Energy Engineering

Analysis of Multiple Annular Pressure in Gas Storage Well and High Pressure Gas Well

Bo Zhang, Lihu Cao, Jinsheng Sun, Nu Lu, Yuqiang Xu — Fri, 28 Oct 2022 00:00:00 +0800

In gas storage wells or high pressure gas wells, annular pressure is an unavoidable threaten for long-term safe production. The more complex situation is multiple annular pressure, which means annular pressure happens in in not only one annulus, but two or more. Such situation brings serious challenge to the identification of well integrity. Therefore, this paper studies the mechanism of multi annular pressure, so as to provide foundation for its prevention and diagnosis. Firstly, the multi-annular pressure is classified according to the mechanism and field data. Then the failure mechanism and function of wellbore safety barrier in the process of passage formation are analyzed. Finally, some suggestions are put forward for the identification and control of multi-annular pressure. The results show that gas storage wells and high-pressure gas wells have the conditions to generate pressure channel, which leads to the expansion of annular pressure from single annulus to the multiple annuli. The pressure channel is composed of tubing string, casing string and cement mantle, and the failures among the three have causal and hierarchical relationship. According to the channel direction, it can be divided into two types: tubing-casing annulus to casing annulus and casing annulus to tubing-casing annulus, of which the former is more harmful. Some measures can be considered to prevent pressure channeling, including improvement of cementing quality, revision of maximum allowable annular pressure and suitable frequency of pressure relief.

Two phase flow simulation of complex oil reservoir based on meshless method

Xian Zhou, Yunfeng Xu — Mon, 24 Jan 2022 00:00:00 +0800

Reservoir is the network rock skeleton of sealed oil and gas trap and the general name of fluid contained in pore fracture and karst cave. Reservoir rock has heterogeneity and complex internal pore structure. Based on the oil water two phase flow model of oil reservoir, the fractal permeability expression is introduced, and the numerical model of fractal oil reservoir two phase flow is established, and the weighted least squares meshless method (MWLS) is used to solve the problem, and compared with the exact solution, the correctness of the method is verified. Considering the influence of different initial crude oil viscosity and different initial formation pressure, the stability and convergence of this method are proved.

Study of CO2 flooding to improve development effect in conglomerate reservoirs

Haihai Dong, Yaguang Qu, Ming Liu, Lei Zhang — Mon, 23 May 2022 00:00:00 +0800

CO₂ flooding for low permeability reservoirs is an effective method to improve recovery and has significant oil enhancement effect. In contrast, no research has been conducted for conglomerate reservoirs with strong non-homogeneity, especially strongly water-sensitive low-permeability conglomerate reservoirs. According to the principle of CO₂ flooding test area selection for conglomerate reservoirs in Xinjiang oilfield, a 15-injection and 43-recovery area was selected as the CCUS test area. Firstly, by evaluating the production dynamics and residual oil in the test area, the residual oil saturation is high, which indicates that the test area has a large residual oil potential. Then the fine tube experimental model was used to obtain the relationship curve between CO₂ flooding efficiency and flooding pressure by varying the flooding pressure to determine the minimum miscible pressure of CO₂ flooding. The minimum miscible pressure of CO₂/crude oil was determined as 24.1 MPa by the fine tube experiment, and the change of phase state of the formation crude oil in the test area after CO₂ injection was further investigated by the CO₂ gas expansion experiment. The results showed that the saturation pressure of the formation crude oil increased significantly after CO₂ injection, and the more CO₂ was injected, the higher the saturation pressure was. The saturation pressure of the CO₂-formation crude oil system reached 31.60 MPa when the injected CO₂ content in the formation crude oil was 55.29 mol%. In order to better simulate the real reservoir conditions in the conglomerate reservoir, the outcrop was taken from the field and processed and made into a two-dimensional planar visualization model to analyze the CO₂ microscopic oil flooding mechanism. After the water flooding, the model was subjected to continuous CO₂ injection gas flooding experiments. The experiments showed that the remaining oil mainly existed in the form of clusters, membranes, columns and blind ends after water flooding, and some remaining oil existed in the form of islands, clusters and membranes after gas flooding, and there was obvious gravity overburden phenomenon. By carrying out CO₂ flooding on the basis of water flooding, the wave efficiency is significantly improved and the degree of recovery is increased. The analysis of the field trial injection effect shows that: the single well CO₂ absorption capacity is significantly improved compared with the water absorption capacity; the profile activation degree in the gas injection stage is better than that in the water flooding stage; the CO₂ injection restores formation pressure quickly; the oil production after gas injection in the trial recovery effect is significantly improved compared with that in the water flooding stage.

Supersonic condensation and separation characteristics of CO2-rich natural gas under different pressures

Weijia Dong — Wed, 30 Nov 2022 00:00:00 +0800

A new natural gas sweetening method, where the CO₂ (carbon dioxide) gas is removed by the combination of condensation due to expansion refrigeration and centrifugal separation, was proposed for the treatment of natural gas rich in CO₂. The structures of the Laval nozzle and the supersonic separator were designed, and the mathematical models of supersonic condensation and swirling separation for CO₂-CH₄ mixture gas were established. The supersonic condensation characteristics of CO₂ in natural gas and the separation characteristics of condensed droplets under different inlet pressures were studied. The study shows that higher inlet pressure results in larger droplet radius and higher liquid phase mass fraction, the influence of centrifugal force is more obvious, and the separation efficiency and removal efficiency of CO₂ are higher. The effects of inlet pressures on the removal efficiency of supersonic separator are complicated, which is controlled by the combined effects of liquefaction capacity of the nozzle and centrifugal separation capacity of the swirl vane.

Energy loss analysis of distributed rooftop photovoltaics in industrial parks

Yu Xiao, Kai Li, Hongqiao Huang, Haibo Tan, Hua Li — Wed, 30 Nov 2022 00:00:00 +0800

The analysis of the loss of distributed photovoltaic power generation system involves the interests of energy users, energy-saving service companies and power grid companies, so it has always been the focus of the industry and society. This paper takes the distributed rooftop photovoltaic power generation project in an industrial park as the object, studies the analysis and calculation methods of line loss and transformer loss, analyzes the change of transformer loss under different temperatures and different load rates, and compares the data and trend of electricity consumption and power generation in industrial parks before and after photovoltaic operation. This paper explores and practices the analysis method of the operation loss of distributed photovoltaic power generation, and provides an important reference for the benefit analysis and investment cost estimation of distributed photovoltaic power generation system in industrial parks.

Key optimization issues for renewable energy systems under dual carbon target: Current states and perspectives

Bo Yang, Zhengxun Guo, Jingbo Wang, Chao Duan, Yaxing Ren, Yixuan Chen — Thu, 21 Jul 2022 00:00:00 +0800

The United States, Japan, Canada, the European Union, and other developed countries and regions have all formulated climate strategies and pledged to achieve net-zero CO2 emissions by 2050. Besides, China announced the “dual carbon target” in September 2020 which aims to achieve “carbon peak” by 2030 and “carbon neutrality” by 2060 [1]. In order to achieve low-carbon development, various renewable energies (wind, solar, wave energy, fuel cell, etc.) have become the main candidates for energy conservation and emission reduction [2]. Furthermore, the current energy structure and power generation mode have achieved dramatic transformation.

Due to the inherent strong intermittent and randomness characteristics of renewable energy, the integration of large-scale renewable energy leads to a series of tricky obstacles for current power system, i.e., (a) Accurate modeling of large-scale integrated systems; (b): Precise power forecast of renewable energy; (c) Optimal planning and dispatching of distributed generation; (d) Reliability and security analysis of renewable energy systems and grid and so on [3-5]. It is difficult yet crucial to undertake some advanced techniques in the modern power system to ensure the power generation output can be effectively optimized and consumed. Hence, the exploitation and implementation of various advanced techniques to deal with the reasonable consumption and optimization of renewable energy systems are imperative. This paper provides a comprehensive and systematic statement of the above problems and proposes several promising perspectives for further study.

Evaluation of Process and Economic Feasibility of Implementing A Topping Cycle Cogeneration

Unique Karki, Bhaskaran Gopalakrishnan — Wed, 30 Nov 2022 00:00:00 +0800

Industrial applications that require steam for their end-uses generally utilize steam boilers that are at higher size than what is typically required. Similarly, gas turbine-based power plants corroborate a gas turbine system and may eventually relieve the exhaust into the atmosphere. This paper focuses on the economic and technical feasibility of a topping cycle combined heat and power (CHP) system. It does so by increasing the load on an existing, underutilized industrial boiler or a gas turbine. A decision support tool (COGENTEC) was developed to evaluate the technical and economic feasibility of a topping cycle CHP system, which can emulate a given facility’s steam or gas system and its operational parameters with steam turbines. First, it assists a user to realize the point of break-even (fuel cost incurred and cost savings) at the desired steam flow rate for a corresponding boiler or a gas turbine-based CHP system. Second, to understand the relationship between various variables, it also conducts sensitivity analysis between energy usage, cost savings, and payback of the investment on operating parameters. The research provides necessary insights into the most appropriate parameters that enables a CHP system to be technically and economically advantageous. The research determines that the fuel cost, electricity cost, and steam flow rate are the most important parameters for a payback on the investment.

Management and Capacity Optimization of Photovoltaic, Energy Storage, Flexible Building Power System

Wed, 30 Nov 2022 00:00:00 +0800

Carbon emissions from building operation account for a large proportion of the total carbon emissions, and the key to carbon reduction lies in replacing the use of non-renewable fossil fuels with electrification of production and living. Considering the trend that the carbon trading market is gradually expanding to the building sector, this paper proposes an optimal operation scheme for the photovoltaic, energy storage, flexible building power system(PEFB). Based on the model of conventional photovoltaic(PV) and energy storage system, the mathematical optimization model of the system is established by taking the combined benefit of the building to the economy, society and environment as the optimization objective, taking the near-zero energy consumption and carbon emission limitation of the building as the main constraints. The optimized operation strategy proposed in this paper is able to give optimal results by making a trade-off between user benefit and the environmental friendliness of the building. The influence of different groups of carbon price and carbon emission baseline about the combined benefit of buildings is further analyzed. The efficiency and effectiveness of the proposed methods are verified by simulation.

Relationship between Industrial Coupling Coordination and Carbon Intensity in the Bohai Rim Economic Circle

Mei Song, Liyan Zhang, Mingxin Zhang, Dandan Li, Yaxu Zhu — Wed, 18 Nov 2020 00:00:00 +0800

Coordinated development of new high-tech industries and traditional industries is crucially important for economic growth, and it has become a focus of academic and governmental bodies. This study uses a model involving the degree of industrial coupling and coupling coordination to determine the level of coordinated development and to further analyze the correlation between regional industrial coupling coordination and carbon intensity of the seven provinces in the Bohai Rim Economic Circle (BREC). The results are as follows. (1) There is a negative correlation between industrial coupling coordination and carbon intensity. (2) The degree of industrial coordination of Beijing, Tianjin, and Shandong is significantly higher than other provinces in the BREC, as both the high-tech industries and traditional industries of these three provinces have reached a high level of development and achieved high coupling. The high-tech industries of the three provinces show positive changes, whereas the traditional industries show negative changes, which indicates that the new high-tech industries are driving the upgrading of the traditional industries by the application of high technologies. (3) From 2011 to 2016, the number of provinces with a low degree of high-tech and traditional industrial coordination fell from three to one. The traditional industries in Hebei and Inner Mongolia have been upgraded by strengthening their technological innovation with the introduction of rapid high-tech industrial development. These findings are a useful reference for regional industrial coupling coordination and carbon emission reduction.

The The Impact of Greenization on the Marginal Utility of Carbon Emission Intensity and Its Influential Factors in China

Adham Liu — Fri, 25 Dec 2020 00:00:00 +0800

Abstract: The impact of greenization on the marginal utility of carbon emission intensity and the factors influencing their relationship in China were evaluated in this study. China’s greenization level was evaluated by an index system and a comprehensive index method, carbon emission intensity was developed using the standard conversion coefficient of coal equivalent and carbon emission coefficient. The impact of greenization on the marginal utility of carbon emission intensity was evaluated by an elastic formula, and the factors were verified by a regression analysis. The results and policy implications were as follows. (1) China’s greenization level displayed a constantly increasing trend. The carbon emission intensity followed a continuous downward trend, while the impact of greenization on the marginal utility of carbon emission intensity was declining. (2) The level of urbanization and scientific and technological development had negative impacts on the diminishing marginal utility of carbon emission intensity. The energy consumption structure had a positive impact on the diminishing marginal utility of carbon emission intensity under the diminishing impact of greenization. The living standards of the population, environmental regulation intensity, and environmental quality have different influences under different conditions.

Factor Decomposition and Econometric Analysis of the Regional Carbon Emission from Energy Consumption from the Perspective of Industrial Structure in Shandong Province of China

weifeng gong, baoqing zhu, chuanhui wang — Wed, 02 Jun 2021 00:00:00 +0800

The energy consumption and carbon emissions of the Chinese Province of Shandong are relatively large when compared to the rest of China. Under the backdrop created by the “13th Five-Year Plan” and the “Replacing Old Growth Drivers with New Ones” in China, in-depth research in carbon emissions from energy consumption has important practical significance for carbon emission reduction and structural adjustment in Shandong Province and throughout China. Based on the perspective of industrial structure, the extended Kaya identity to measure the carbon emissions from energy consumption of the Primary industries (Resources and Agriculture) and Secondary industries (Manufacturing and Construction) and Tertiary industries (Retail and Service) was utilized in Shandong Province from 2011 to 2017. The carbon emissions among industries in Shandong Province were empirically analyzed using the Logarithmic Mean Divisia Index decomposition approach. The results were follows: (1) under the three industrial dimensions, the energy structure effect and the energy intensity effect have a restraining influence on the carbon emissions of the three industries. (2) The development level effect and the employment scale effect play a pulling role in carbon emissions. (3) From the perspective of the employment structure effect of the primary industry, there is a restraining effect on carbon emissions, while the employment structure effects of the secondary and tertiary industries play a pulling role in carbon emissions, and the employment structure effect of the tertiary industry has a greater pulling effect on carbon emissions than the secondary industry.

Behaviors of Multi-Stakeholders under China’s Renewable Portfolio Standards: A Game Theory-Based Analysis

zhenming sun, Bing Wang, Kailei Deng, Liting He — Sat, 17 Jul 2021 00:00:00 +0800

China has implemented both quantitative and price incentive policies for renewable energy development since 2019, and been currently in the policy transition stage. The implementation of quota policy is in difficulty by the interest involvement of multi-stakeholders of power generation enterprises, power grid companies, power users, local governments and central government. Based on China's Renewable portfolio standards policy and power system reform documents, this research sorted out the core game decision problems of China's renewable energy industry, and established a conceptual game decision model of renewable energy industry from three aspects of local governments, power generation enterprises and power grid companies. Results reveal that for local governments, the probability of meeting the quota and the earnings or punishments for the quota completion are the major determinants for active participation in the quota supervision. For power grid firms, the willingness to accept renewable electricity quotas depends on the extra cost of receiving renewable electricity and governmental incentives. It is reasonable from the theoretic perspective to implement the renewable energy quotas policy on the power generation side. The electricity reform will help clarify the electricity price system and increase the transparency of the quota implementation process. Policy implications are suggested to achieve sustainable development of renewable energy industry from price incentives and quantity delivery.

A Low Cost, Real Time Rooftop IoT Based Photovoltaic (PV) System for Energy Management and Home Automation

Sat, 04 Dec 2021 00:00:00 +0800

This work discusses the importance of monitoring and energy management of green energy resources in
order to minimize the negative impacts of electricity generation by regular power plants. The paper
introduces a highly efficient, low cost rooftop photovoltaics (PV) solar panel system which can provide
monitoring, controlling and automation. The proposed system is based on Internet of Things (IoT) and can
be used to control different utilities in any premises automatically or set by the user defined priority list, as
compared to the existing IoT based PV systems which can only perform monitoring and maintenance of the
PV panels or only certain parameters, i.e., temperature, dust, etc. This is a new step in improving the
efficiency of IoT based PV system where the facility loads are automated by the IoT network. The proposed
system can also provide a constant feedback about different parameters, i.e., voltage, dust, sun irradiance
and humidity, etc., via low cost open source platforms for telemonitoring and controlling purposes. The
results show that the proposed system provides a high efficiency to energize the utilities and utilize the
available energy as compared to the manual control. The proposed system can also easily be enhanced and
implemented for any large scale monitoring and energy management

Energy Services as a Business: Eco-Transformation Logic to Support the Low-Carbon Transition

Oleksandr Victorovich Novoseltsev — Sat, 04 Dec 2021 00:00:00 +0800

The transition to low-carbon development has been recognized as one of the most important directions for the transformation of national economies in most countries. Today we can identify two of the most common service-oriented logical models of this transition. These are models of Service-Dominant Logic and Product-Service Systems that are used in this paper to create a service-oriented platform for stimulating business development in the field of energy services. The establishment of such a platform is being considered on the basis of the conceptual provisions of the global business ecosystem. Such a platform has been found to be a powerful tool for systematic coordinated cooperation among actors in both energy and energy services and related production markets, ultimately unleashing the benefits of synergies, resulting from such cooperation. The logical models of attracting energy service companies to the creation of virtual communities (centers) for large-scale implementation of measures in the field of energy efficiency and renewable energy sources are presented in detail.

Assessment Framework of Green Intelligent Transformation of Small Hydropower in China

Jun Shi — Mon, 24 Jan 2022 00:00:00 +0800

With the comprehensive promoted construction of the establishment of green small hydropower, the defects of existing small hydropower station are gradually emerging, and it is necessary to implement green intelligent transformation to promote the construction of energy internet in China. This study focus on constructing a green intelligent planning and transforming assessment framework, which assists management department to filtrate the small hydropower stations can be transformed reasonably. Firstly, power station economy, ecological environment, technical safety management and social benefits are involved in the assessment index system. Secondly, multi-expert judgment aggregation based on fuzzed comparison scale is put forward to calculate the index value and evidence synthesis is used to comprehensively assess the feasibility of green and intelligent planning and transformation for several small hydropower stations. The simulation case analysis shows the constructed assessment framework can reflect the actual situation of objectives properly and would provide decision-making basis for green and intelligent planning and transformation of small hydropower stations.

Bi-level Energy Management Model of Grid-connected Microgrid Community

Houqi Dong; Haibin Cao, Yongjie Ren — Fri, 01 Apr 2022 00:00:00 +0800

As the proportion of renewable energy power generation continues to increase, the number of grid-connected microgrids is gradually increasing, and geographically adjacent microgrids can be interconnected to form a Micro-Grid Community (MGC). In order to reduce the operation and maintenance costs of a single micro grid and reduce the adverse effects caused by unnecessary energy interaction between the micro grid and the main grid while improving the overall economic benefits of the micro grid community, this paper proposes a bi-level energy management model with the optimization goal of maximizing the social welfare of the micro grid community and minimizing the total electricity cost of a single micro grid. The lower-level model optimizes the output of each equipment unit in the system and the exchange power between the system and the external grid with the goal of minimizing the operating cost of each microgrid. The upper- level model optimizes the goal of maximizing the social welfare of the microgrid. Taking a microgrid community with four microgrids as an example, the simulation analysis shows that the proposed optimization model is beneficial to reduce the operating cost of a single microgrid, improve the overall revenue of the microgrid community, and reduce the power interaction pressure on the main grid.

Simulating Error-opening of Pressure Relief Valves of a Station on a Continuous Undulating Oil Pipeline with Large Elevation Difference

Xiaohua Chen, Caifu Lan, Honghao Zheng, Wang Li, Chao Zhao, Wenjun Dang — Mon, 23 May 2022 00:00:00 +0800

This research focuses on the safety issues associated with the pressure relief system of a continuous undulating oil pipeline with large elevation difference. Due to the large elevation difference, there is high hydro-static pressure in the pipeline, which may cause error-opening of the pressure relief valves. The oil is then discharged into pressure relief tanks, and spilling over accident of the pressure relief tanks may occur. Thus, simulating the error-opening situations of the pressure relief valves, investigating the variation of the discharge volume as well as velocity, and making judgement of the possibility of spilling over accident are necessary. Then improvement to the pressure relief system reasonably according to the analysis results can be performed. A station along a continuous undulating oil pipeline with large elevation difference is studied, which is named B station in this paper. By OLGA software, simulation model of the pressure relief system of B station is established, and the accuracy of the model is verified by reconstructing a real accident and making a comparison with actual accident data. On this basis, for error-opening of the pressure relief valves at the inlet and outlet of B station, simulation is performed to investigate variations of the discharge velocity, discharge flowrate, accumulated discharge volume and ventilation volume of the vent valve. The discharge velocity is found to be over the allowed maximum velocity allowed for safety consideration. According to the accumulated discharge volume, it is inferred that spilling over of the pressure relief tanks will be caused once error-opening of the pressure relief valve occurs. Also it is judged that the existing breathing valve can not satisfy the ventilation requirement in case of failure of the pressure relief valves. From these simulation results, it is proposed that increasing the number of vent valves, replacing the manual valves with electrically operated valves, and employing security control interlock protection program are improvement measures to guarantee safe, efficient and reliable operation of the pressure relief system at B station.

T-shaped Transmission Line fault location Based on Phase-angle Jump Function Checking

XIE JIA AN — Thu, 21 Jul 2022 00:00:00 +0800

In order to effectively solve the dead-zone and low-precision of T-shaped transmission line fault location, a new T-shaped transmission line fault location algorithm based on phase-angle jump function checking is proposed in this paper. Firstly, extract the 3-terminal synchronous fundamental positive sequence voltage and current phasors when the fault occurs and use them to realize the T-shaped fault branch selection; Secondly, use the condition of equal amplitude of the fundamental positive sequence voltage phasor at the fault point to calculate all roots (including real root and imaginary root); Finally, the phase-angle jump function is used for checking calculation, and then the only real root can be determined as the actual fault distance, thereby achieving the purpose of high-precision fault location. MATLAB simulation results show that the proposed new algorithm is feasible and effective with high fault location accuracy and good versatility.

Research on Downscaling Method of Meteorological Data Spatial Combination Applied to Photovoltaic Power Forecast

yan jin — Thu, 21 Jul 2022 00:00:00 +0800

Aiming at the problem of low spatial resolution of meteorological data output by numerical model in photovoltaic power prediction, a combined downscaling method of meteorological data is proposed, which considers elevation (DEM), vegetation index (NDVI), aspect, longitude and latitude and other factors. Based on the correlation between meteorological data and DEM, NDVI, aspect, longitude and latitude, this method introduces DEM and local Moran index to improve the downscaling model. At the same time, EOF iterative analysis is carried out by using the original and measured meteorological data. The results are obtained by equal weight average method, and the spatial resolution is improved to 100m, Finally, the downscaling results are verified by the measured data in the study area. The results show that: after downscaling, the error between the meteorological data and the measured value is significantly less than that between the original meteorological data and the measured value, which can better make up for the lack of future meteorological changes in the area predicted by the numerical model, and provide a more reliable meteorological basis for improving the prediction accuracy of photovoltaic power.

Two-Stage Low-Carbon Economic Dispatch of Integrated Demand Response-Enabled Integrated Energy System with Ladder-Type Carbon Trading

Song Zhang, Wensheng Li, Zhao Li, Xiaolei Zhang, Zhipeng Lu, Xiaoning Ge — Fri, 28 Oct 2022 00:00:00 +0800

Driven by the goal of “carbon neutrality” and “emission peak”, effectively controlling of system carbon emissions becomes significantly important. To this end, a novel two-stage low-carbon economic scheduling framework which considers the coordinated optimization of ladder-type carbon trading and integrated demand response (IDR) is proposed for integrated energy system (IES), where the first stage determines the energy consumption plan of users by leveraging the price-based electrical-heat IDR, while the second stage minimizes the system total cost to optimize the outputs of generations with consideration of the uncertainty of renewables. In addition, to fully exploit the system's emission reduction potential, a carbon trading cost model with segmented CO2 emission intervals is built by introducing a reward-penalty ladder-type carbon trading mechanism, and the flexible thermal comfort elasticity of customers is taken into account by putting forward a predicted mean vote index on the load side. The two-stage model is resolved by the CPLEX optimizer, and the study results on a modified IES situated in North China show the proposed model can effectively reduce carbon emissions and guarantee the economical operation of the system.

Diesel Engine Performance Fueled by Biodiesel – Ed Blend

Fri, 28 Oct 2022 00:00:00 +0800

Diesel engines are widely used in various sectors, such as transportation, industry, and agriculture. This is an internal combustion engine with high thermal efficiency, which also uses biodiesel fuel, an environmentally friendly, non-toxic, and low sulfur content. Biodiesel has been around for a long time due to its similar characteristics to diesel fuels which has limited availability. However, several disadvantages are associated with biodiesel, such as poor volatility and high viscosity, which reduces engine performance. Therefore, this study was carried out to improve the diesel engine performance by mixing biodiesel with Eco diesel (ED), an additive produced from natural ingredients that is dissolvable in biodiesel. The results showed that biodiesel-ED mixture could improve engine performance and the optimum performance was at a speed of 3000 RPM on 43.30 (kW), 124.93 (N.m) of the engine torque, and 2.45 (kg/kW.s) of the specific fuel consumption.

Energy Management of Networked Smart Railway Stations Considering Regenerative Braking, Energy Storage System, and Photovoltaic Units

Saeed Akbari, Seyed Saeed Fazel, Hamed Hashemi-Dezaki — Fri, 28 Oct 2022 00:00:00 +0800

In the form of a smart grid, the networking of microgrids has received a great deal of attention. In this paper, a set of smart railway stations, which are assumed as microgrids, are connected together. It has been tried to manage the energy exchanged between the networked microgrids in order to reduce received energy from the utility grid. Also, the operational costs of stations under various conditions are decreased by applying the proposed method. The smart railway stations are studied in the presence of photovoltaic (PV) units, energy storage systems (ESSs), and regenerative braking strategies. Studying regenerative braking is one of this research’s contributions. Moreover, the stochastic behaviors of the ESS’s initial state of energy and the uncertainty of PV power generation are taken into account through a scenario-based method. The networked microgrid scheme of railway stations (based on coordinated operation and scheduling) and independent operation of railway stations are studied in this article. The proposed method is applied to realistic case studies, including three stations of Line 3 of Tehran Urban and Suburban Railway Operation Company (TUSROC). The rolling stock is simulated in the MATLAB environment. Thus, the coordinated operation of networked microgrids and independent operation of railway stations are optimized in the GAMS environment utilizing mixed-integer linear programming (MILP).

Numerical Simulation of Contamination Accumulation Characteristics of Composite Insulators in Salt Fog Environment

Yu kun Lv, Ze ze Chen, Quan zhi Ge, Qian Wang, Ya Zhao Zhang — Wed, 30 Nov 2022 00:00:00 +0800

To investigate the fouling characteristics of the composite insulator surface under the salt fog environment, the FXBW-110/120-2 composite insulator was taken as the research object. Based on the field-induced charge mechanism, the multi-physical field coupling software COMSOL was used to numerically simulate the fouling characteristics, explored the calculation method of ESDD, and demonstrated its rationality. Based on this method, the pollution characteristics of the composite insulator under the pollution fog environment were studied, and the influence of wind speed, droplet size, and voltage type on the pollution characteristics of the composite insulator was analyzed. The results showed that: with the increase in wind speed, the amount of accumulated pollution of insulator increases in the range of droplet size, and the relationship between wind speed and accumulated pollution is approximately linear; at the same wind speed, the amount of accumulated pollution increases with the increase of droplet size under the action of DC voltage; when there is no voltage, the amount of dirt on the upper surface of the insulator is more than that on the lower surface, while it is the opposite under DC voltage.

Simulation Research on Coal-Water Slurry Gasification of Oil-Based Drilling Cuttings Based on Fluent

Liang Hu — Mon, 09 Oct 2023 00:00:00 +0800

In this paper, based on Fluent software, a five-nozzle gasifier reactor was established to simulate the gasification process of oil-based drilling cuttings coal-water slurry, and the influence of concentration and oxygen/carbon atom ratio on the gasification process of oil-based drilling cuttings coal-water slurry was studied. The results show that when the oxygen flow is constant, the outlet temperature of gasifier decreases, the content of available gas increases, and the carbon conversion rate decreases with the increase of concentration; When the ratio of oxygen to carbon atoms is constant, the available gas content rises and the temperature rises with the increase of the concentration, and the carbon conversion rate reaches the maximum value when the concentration of oil-based drilling cuttings coal-water slurry is 65%; When the concentration is constant, the effective gas content decreases and the outlet temperature rises with the increase of the oxygen/carbon atom ratio, and the carbon conversion rate reaches 99.80% when the oxygen/carbon atom ratio is 1.03. It shows that this method can effectively decompose the organic matter in oil-based drilling cuttings and realize the efficient and cooperative treatment of oil-based drilling cuttings.

An Experiment study on exhaust-gas heat exchanger for small and medium-sized marine diesel engine

Li Luo, Guannan Xi — Fri, 28 Oct 2022 00:00:00 +0800

Abstract: This paper aims to design a special exchanger to recover the exhaust gas heat of marine diesel engine used in small and medium-sized fishing vessels, which can be used to heat water up to 55–85°C for membrane desalination device to produce fresh water. A new exhaust-gas heat exchanger of fins and tube, with a reinforced heat transfer tube section, unequal spacing fins, a mixing zone between the fin groups and four routes tube bundle, was designed. Numerical simulations were also used to provide reference information to the structure design. Experiments were carried for exhaust gas waste heat recovery from a marine diesel engine in an engine test bench by using the heat exchanger. The experimental results show that the difference between heat absorption by water and heat reduction of exhaust gas is less than 6.5%. After the water flow rate was adjusted, the exhaust gas waste heat recovery efficiency is higher than 70% and the outlet water temperature of the exhaust-gas heat exchanger is in the range of 55-85℃ at different engine loads. This means that the heat recovery from the exhaust gas of marine diesel engine meets the requirement to drive membrane desalination device to produce fresh water for fishermen working in small and medium-sized fishing vessels.

Determination of Effectiveness of Energy Management System in Buildings

Vivash Karki, Roseline Mostafa, Bhaskaran Gopalakrishnan, Derek R. Johnson — Wed, 30 Nov 2022 00:00:00 +0800

Building Energy Management Systems (BEMS) are computer-based systems that aid in managing, controlling, and monitoring the building technical services and energy consumption by equipment used in the building. The effectiveness of BEMS is dependent upon numerous factors, among which the operational characteristics of the building and the BEMS control parameters also play an essential role. This research develops a user-driven simulation tool where users can input the building parameters and BEMS controls to determine the effectiveness of their BEMS. The simulation tool gives the user the flexibility to understand the potential energy savings by employing specific BEMS control and help in making intelligent decisions. The simulation is developed using Visual Basic Application (VBA) in Microsoft Excel, based on discrete-event Monte Carlo Simulation (MCS). The simulation works by initially calculating the energy required for space cooling and heating based on current building parameters input by the user in the model. Further, during the second simulation, the user selects all the BEMS controls and improved building envelope to determine the energy required for space cooling and heating during that case. The model compares the energy consumption from the first simulation and the second simulation. Then the simulation model will provide the rating of the effectiveness of BEMS on a continuous scale of 1 to 5 (1 being poor effectiveness and 5 being excellent effectiveness of BEMS). This work is intended to facilitate building owner/energy managers to analyze the building energy performance concerning the efficacy of their energy management system.

A Displacement field variable modeling method for heterogeneous materials in wind power blade core plates

Ying He, Yongshuang Wen, Xuemei Huang, Leian Zhang, Rujun Song, Chang Li — Wed, 30 Nov 2022 00:00:00 +0800

In order to study the mechanical properties of the heterogeneous core plate of the wind turbine blade, a modeling method of the core plate based on displacement field variables was proposed. Firstly, the material characteristics of the wind turbine blade core plate were modeled according to the theory of modeling heterogeneous material characteristics. Secondly, the three-point bending finite element model of the wind turbine blade core plate was solved by the display dynamic equation to obtain the deformation pattern and force-deformation relationship of the core plate. Finally, the three-point bending static test was conducted to compare with the finite element analysis. The test results showed that: the damage form of the wind turbine blade core plate included elasticity, yield, and failure stages. The main failure modes were plastic deformation, core material collapse, and panel-core delamination. The failure load measured by the test was 1.59 kN, which was basically consistent with the load-displacement results obtained by the simulation, with a difference of only 1.9%, which verified the validity and reliability of the model. It provided data references for wind turbine blade structure design.

Solar Energy Power Generation and Forecasting: A State-of-the-Art Survey

H.J. Shao, Xing Deng, Feipeng Da, Xia Wang — Wed, 30 Nov 2022 00:00:00 +0800

Photovoltaic power generating is one of the primary methods of utilizing solar energy resources, with large-scale photovoltaic grid-connected power generation being the most efficient way to fully utilize solar energy. This paper attempts to provide a survey investigation and technical analysis of machine learning-related approaches, statistical approaches, and optimization techniques for solar power generation and forecasting, with the intention of providing reference strategies for relevant researchers as well as potential implementation. In particular, deep learning can theoretically deal with arbitrary nonlinear transformations through proper model structural design, such as hidden layer topology optimization, objective function analysis to save information that can improve forecasting accuracy while filtering out irrelevant or less affected data for forecasting. In addition, to assess the present state of new energy development and market trends at home and abroad, scenario application and PV system investment methods are offered.

Evaluation of Long-term Operational Stability of Underground Gas Storage in Salt Rock with Interlayer Based on Variable Weight Method

Jun Zhou, Shijie Fang, Guangchuan Liang, Qing Li, Xinyu Huang — Fri, 28 Oct 2022 00:00:00 +0800

Salt rock has extremely low permeability, good creep performance and self-recovery characteristics of damage, so it has become an internationally recognized ideal medium for underground energy storage. Compared with the salt domes or thick salt rock formations in the United States and Russia, the Chinese salt rock has the characteristics of "many interlayers, thin single layers, impurities in mudstone interlayers". Gas storages are built or modified in this interbedded salt rock mass, whether it is Early-stage water-dissolving cavity construction or long-term operation stability are inevitably affected by mudstone interlayers. Therefore, it is necessary to conduct research on the long-term operation stability of interbedded salt rock gas storage. This paper constructs a long-term stability evaluation system for underground gas storage, determining the impact factor scoring model according to the simulation of the cavern creep of the gas storage. Introduce the variable weight theory on the basis of the traditional constant weight method, determining the variable weight of the evaluation index, and calculate the comprehensive stability score based on the sub-item score of each index. Compared with the traditional constant weight method, the evaluation results are more rigorous and objective.

A single-ended protection principle for LCC-VSC-MTDC system with high resistance fault tolerance

Chuanjian Wu, Dahai Zhang, Jinghan He — Fri, 28 Oct 2022 00:00:00 +0800

Line-commutated converter-voltage source converter (LCC-VSC) power transmission technology does not have the problem of commutation failure, and can support long-distance and large-capacity transmission of electric energy. However, factors such as topology, control strategy, and short-circuit capacity make the traditional protection principle not fully applicable to LCC-VSC hybrid transmission systems. To enhance the reliability of hybrid DC system, a single-ended principle based on transmission coefficient is proposed. First, the equivalent circuit of the LCC-VSC hybrid DC system is analyzed, and the expression of the first traveling wave is deduced accordingly. Then, the concept of multi-frequency transmission coefficient is proposed by analyzing the amplitude-frequency characteristics of each element. Finally, the LCC-VSC DC system model is built to verify the reliability and superiority of the principle. Theoretical analysis and experimental verification show that the principle has strong interference resistance.

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Admin Manager — Wed, 10 Jun 2020 00:00:00 +0800

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Improved Thermal Efficiency of Salinity Gradient Solar Pond by Suppressing Surface Evaporation Using an Air Layer

Hameed Balassim Mahood — Fri, 16 Oct 2020 00:00:00 +0800

Renewable energy, especially solar power, offers an important source of sustainable and reliable energy that can be exploited to meet growing global demand and reduce dependence on fossil fuels. Salinity gradient solar ponds (SGSPs) – are attracting increasing interest. They provide a tremendous way to collect and store solar radiation as thermal energy, and can help meet the critical need for sustainable ways of producing fresh water. However, surface evaporation results in the loss of both water and heat, reducing efficiency and increasing maintenance. This study therefore theoretically investigates the effect on temperatures within an SGSP when its surface is covered with a layer of air encased in a nylon bag. An earlier SGSP model was slightly modified to add the air layer and to estimate the temperature distributions of the upper layer or the upper convective zone (UCZ) and the bottom layer or lower convective zone (LCZ). The results for a year-long period showed that adding the air cover increased the LCZ temperature to a maximum of 94 oC in July, with a total average increase of about 9% over the uncovered pond. In the UCZ, temperatures showed an average increase of approximately 45%, reaching a maximum of 34 ^oC. The temperature of the air layer was meanwhile found to be close to the ambient temperature and behaved identically. These findings invite future experimental and theoretical investigations into the use of air layers to prevent surface evaporation, thereby enhancing the efficiency of SGSPs as a source of clean energy.

R Research on distribution network full cost-benefit optimization considering different renewable energy penetration

yu xue — Fri, 16 Oct 2020 00:00:00 +0800

To further study the impact of renewable energy penetration on the technical transformation of distribution networks. Based on the output power characteristics of wind power and photovoltaics, a renewable energy grid-connected capacity model and a distribution network full cost-benefit model were constructed. Based on this, with the goal of maximizing the comprehensive income of the distribution network and the renewable energy penetration rate, establishing the technical reform optimization model, and searching for the optimal solution through the improved NSGA-Ⅱ algorithm. Finally, the effectiveness of the proposed model was verified by setting up three scenarios of simultaneous wind power, grid-connected wind power, grid-connected wind power, and grid-connected photovoltaic power.

Research on Effect of Icing Degree on Performance of NACA 4412 Airfoil Wind Turbine

Bin Cheng — Fri, 16 Oct 2020 00:00:00 +0800

In order to study the growth characteristics of wind turbine blade icing in a natural environment, and the effect of icing on the wind turbine blade tip speed ratio and wind energy utilization coefficient under working conditions. In this paper, the icing test of the NACA4412 airfoil wind turbine was carried out using the natural low temperature wind turbine icing test system. An evaluation model of icing degree was established, and the influence of wind speed and icing degree on the performance parameters of wind turbines was compared and analyzed. It is shown that icing is mainly concentrated on the leading edge of the blade and the windward side. The icing on the leeward surface is concentrated near the leading edge of the blade. The amount of icing varies significantly along the direction of blade expansion, with the least amount of ice accumulation at 0.2R, followed by 0.6R, and most at 0.95R. At the beginning of the experiment, the icy thickness at the 0.2R, 0.6R and 0.95R locations increased at a rate of 12.03%, 8.87% and 6.00% respectively, and then the growth rate gradually decreased and stabilized. At the same wind speed, the blade tip speed ratio and wind energy utilization coefficient are inversely related to the change trend of the icing degree. When the blade icing degree is 0.82%, 1.49% and 2.73%, the maximum tip speed ratio is reduced by 7.1%, 14.1% and 21.2% and the maximum wind energy utilization coefficient is reduced by 36.3%, 51.2% and 61.6% respectively.

Investigation of Core Loss Calculation Methods for Nanocrystalline Core in Medium Frequency Range

Yunxiang Guo, Cheng Lu, Feng Yu, Liang Hua, Xinsong Zhang — Fri, 16 Oct 2020 00:00:00 +0800

Nanocrystalline core is often adopted in high-power medium-frequency transformer, whose excitation voltage is usually a rectangular wave with an adjustable duty ratio. In this paper, several kinds of methods are proposed for core loss calculation under non-sinusoidal voltage excitation by modifying the original Steinmetz equation (OSE). Firstly, these correction methods are compared in theory, and their analytical equations under rectangular voltage with an adjustable duty ratio are deduced. Then, a hysteresis loop measurement system is established to measure the core loss density of a nanocrystalline core. Based on the measured results of the core loss density under sinusoidal voltage excitation, the coefficients of OSE for the core are fitted. Finally, core loss calculation results using the proposed correction methods under different amplitudes and duty ratios are analyzed and compared with the measured values. The results verify the correctness of the theoretical analysis, that waveform-coefficient Steinmetz equation is the most suitable method for loss calculation of nanocrystalline core in medium frequency range when the excitation voltage is a rectangular wave with an adjustable duty ratio.

A Subsynchronous Oscillation Suppression Method Based on Self-Adaptive Auto Disturbance Rejection Proportional Integral Control of VSC-MTDC System with Doubly-Fed Induction Generator-Based Wind Farm Access

Miaohong Su; Haiying Dong, Kaiqi Liu, Weiwei Zou — Fri, 16 Oct 2020 00:00:00 +0800

A subsynchronous oscillation suppression strategy based on self-adaptive auto disturbance rejection proportional integral controller (SAADR-PI) is proposed for doubly-fed induction generator (DFIG)-based wind farm integrated into grid through voltage source converter based multi-terminal direct current (VSC-MTDC). In this strategy, the nonlinear PI controller is constructed by fal function to replace the traditional linear PI controller, and then the tracking differentiator is used to arrange the appropriate transition process in combination with the idea of active disturbance rejection control (ADRC), and the SAADR-PI controller is designed. By applying the controller to the inner loop of the converter on the rotor side of the DFIG, the adaptability of the control parameters of the inner loop to the change of operating conditions of the system can be improved, and the dynamic performance of the system can be improved. The simulation results on the PSCAD/EMTDC show that the SAADR-PI controller can realize the effective suppression of the SSO under different operating conditions of the wind farm via the comparison with the additional subsynchronous damping control (SSDC) of DFIG. Besides, when the suppression method based on SAADR-PI controller on the rotor side of DFIG is combined with the multi-channel variable-parameter additional SSDC of VSC-MTDC converter, the convergence speed of SSO can be improved and the stability of the system can be enhanced.

Accurate Study and Evaluation of Small PV Power Generation System based on Specific Geographical Location

Lian Zhang — Fri, 16 Oct 2020 00:00:00 +0800

As an important new energy, solar energy has been widely used in the world and different types of solar energy systems are used in different fields. The advantages of photovoltaic power generation system are more and more obvious. However, the small-scale photovoltaic power generation system has a wider application in the field of power generation. In this paper, small-scale photovoltaic power generation system is studied in different areas. Based on the determination of photovoltaic model system, four typical geographical locations are selected and PVsyst is applied to the simulation study. The annual power output is 4829kWh, 3444kWh, 4455kWh and 2766kWh for the four typical cities respectively from the simulation results. The results show that the radiation conditions, the optimum tilt angle, the minimum distance and different geographical locations are the main reasons for the difference of power generation. In addition, Changchun City is selected as the experimental area to carry out experimental research to verify the conclusion of the simulation study. The volt ampere characteristic curve and power output curve show that the photovoltaic system has no defects, hot spots, partial shading and damage. The annual total power generation of Changchun is 4119 kwh. Hence, the simulation results are in good agreement with the experimental results. Therefore, the application of small photovoltaic power generation system needs to fully consider the regional conditions to obtain better power generation efficiency.

Wind Farm-Battery Energy Storage Assessment in Grid-Connected Microgrids

Umar Taiwo Salman, Shafiqur Raheman, Luai Muhammad Alhems — Fri, 16 Oct 2020 00:00:00 +0800

Renewable energy (RE) has received much attention in the last few decades and more investment is being attracted across the world to boost its contribution towards the existing energy mix. In the Kingdom of Saudi Arabia (KSA), many studies have been conducted on the potential of renewable energy sources (RES), such as wind, solar, and geothermal. Many of these studies have revealed that the Kingdom is blessed with abundance of RES with wind energy being among the popular ones. This paper presents an analysis of windfarm distributed generation (WFDG) for energy management strategy in the Eastern Province of KSA. The study investigates the possibility of partially powering the load of the area from a wind farm of 100MW installed capacity. The study also investigates the effect of supplementing the WFDG with diesel generators. Based on the historical wind resources and the load data, the cost of electricity is analyzed using a dynamic pricing system. Simulations are carried out using quadratically constrained programs (QCP) available in the General Algebraic Modeling System (GAMS) to obtain the operational cost of the WFDG needed to achieve the target. Furthermore, the dispatch of the battery energy storage system (BESS) is analyzed during the 24 hours’ simulation period.

Energy Retrofitting of School Buildings in UAE

Abdelsalam Aldawoud, Fatma Elzahraa Hosny, Rasha Mdkhana — Fri, 16 Oct 2020 00:00:00 +0800

The opportunities for energy savings by retrofitting of the existing school buildings in the United Arab Emirates (UAE) are significant because of their excessive energy consumption and space cooling demand. In this research, energy modeling and simulation are utilized with the use of DesignBuilder software to examine the influence of various retrofitting measures of air-conditioning (A/C) system and building envelope components on the energy use. Several individual and combined measures are implemented and assessed in order to achieve the main goal of this research of selecting the best course of actions to reduce cooling energy consumption for existing school buildings in UAE. The results show that the intensity of the reduction in cooling energy requirement varies from one retrofitting set of measures to another. The used electricity can be reduced by 29% to provide the required cooling demand with replacing the existing air conditioning equipment with more energy-efficient and properly sized system. A reduction of 21.5% in the annual electricity consumption to provide the required cooling demand can be obtained by adding insulation to the building roof and exterior walls. In addition, reduction in electricity consumption of 57% can be potentially achieved to provide the required cooling load by improving the thermal resistance of the existing school walls, roof and windows combined with high efficiency air conditioning (A/C) system.

Energy Services: A Proposed Framework to Improve Results

Oleksandr Victorovich Novoseltsev — Sat, 17 Oct 2020 00:00:00 +0800

Energy services markets are actively developing around the world, but their growth rates need to be accelerated in order to help the world meet energy policy goals. One barrier to energy services markets is confusion created from different terminology used in different parts of the world. In this context, various definitions of the term “energy service” have been analyzed in this paper and it has been recommended to distinguish between “energy services” and “energy-related services”. The structural and functional features of the energy services market conceptual design and its implementation models, as well as the use of energy service companies (ESCOs) concept has been also investigated. We hope that this standardization will clarify business activity as well as improve the ability for investors and stakeholders to further expand the market, especially considering the recent market impacts of the Covid-19 virus.

Heterogeneous pricing and affordability of residential natural gas consumption: lifestyle-driven or income-determined?

Bing WANG, Yao Yao, Liting He, Xiangqian Pei — Sat, 17 Oct 2020 00:00:00 +0800

With the huge increase in natural gas consumption, the distortion of natural gas prices, especially in the residential sector, is prominently shaped into a heavy burden for public finance. Although the price of residential natural gas stations has been sorted and a price linkage mechanism has been established, the price tolerance of residential natural gas should be considered when the price of residential gas fluctuates with the upstream gas price. Determinants of the price affordability of residential natural gas consumption at different economic levels (Beijing, Nanjing, Zhengzhou) were investigated by field survey and online investigation and analyzed by a factor analysis and discriminant analysis. The results show that most residents are not sensitive to the price of natural gas, and their motivation for replacing gas with other energy is not strong. More than half of the residents have strong natural gas price affordability, while the weakest affordability occurred in poor research areas. The income level of the consumers, the convenience and reliability of natural gas, and the duration of natural gas consumption are the top three factors affecting the affordability of natural gas prices for residents. Policy implications are proposed to ease the implementation of natural gas price reform.

Dissolution and degradation of spent radioactive cation exchange resin by Fenton oxidation combining microwave

Jiangbo Li, Lielin Wang, Hua Xie, Xiaoyu Li, Zhiqiang Feng, Wenxiu Zhang — Sat, 17 Oct 2020 00:00:00 +0800

The microwave-enhanced Fenton process is surely a favorable technique in degrading spent radioactive cation exchange resins. A fresh strategy for degrading spent radioactive cation exchange resin was proposed through several design experiments. This unique microwave enhancement Fenton reaction has the highest degradation rate for spent radioactive cation exchange resin degradation (98.55% after 60 min), compared with Fenton (99% after 180 min) and electro-Fenton (92% after 300 min). According to the report survey of XRD, FT-IR and NMR analysis, it’s been statistically added that the degradation process of cation exchange resin will formulate carbon dioxide, sulfate and small molecular compounds. A model for explaining the degradation mechanism of cation exchange resin was constructed. The microwave was implemented to boosting the concentration of hydroxyl radicals in the Fenton reaction, infiltrating the cation resin to form a channel that facilitates the entry of the hydroxyl group into the interior of the resin. This paves the way for speeding up the treatment of spent radioactive ion exchange resin, which could exert significant influence on the road for degradation of radioactive organic matter.

Research on Optimal Matching of Heating Ventilation Air Conditioning System Based on Energy Saving Requirements

Dongsheng Xu — Sat, 17 Oct 2020 00:00:00 +0800

With the continuous development of society and the progress of science and technology, the living standards of the people also constantly improve, people pay more and more attention to the pursuit of material life, and the living space of everyday life and office space requirements are also rising, the air conditioning has become the essential in people daily life a kind of electrical equipment. The traditional optimal matching methods of HVAC (heating ventilation air conditioning) system have common problems such as long matching time, low matching accuracy and many matching times. The application of the best matching method of HAVC system based on energy saving requirements is in line with the requirements of strengthening energy saving, and it is also an urgent need to actively respond to global climate change and establish a responsible image through energy saving. For this situation, this study proposes an optimal matching method for HVAC systems based on operating energy consumption. By analyzing the operation characteristics and energy consumption of hvac refrigerator, calculating the operating energy consumption of hvac system; Based on the results of energy consumption, analyzing the capacity matching relationship among photovoltaic modules, fans and batteries in hvac system, to construct the best matching model between the three groups of devices. The experimental results show that the method proposed in this study has shorter matching time, higher matching accuracy and fewer matching times.

An energy efficiency improvement method for manufacturing process based on ECRSR

Haiming Sun, Quande Dong, Cuixia Zhang, Jianqing Chen — Sat, 17 Oct 2020 00:00:00 +0800

The improvement of energy efficiency is considered as one of the key to the sustainable development of manufacturing enterprises. This paper proposes an energy efficiency improvement method for manufacturing process. Based on the analysis of the characteristics of energy consumption in the manufacturing process, the necessary energy consumption model, assistant energy consumption model and ineffective energy consumption model are constructed for identifying the process energy consumption attribute of the manufacturing process. Then, the relationship model of energy consumption is constructed, and the optimization method of manufacturing process for energy efficiency is proposed based on ECRSR (Eliminate, Combine, Rearrange, Simplify and Recovery). Finally, taking the production process of an injection molding machine in a workshop as an example, the results show that the average hourly power saving rate of single machine is 37.3%, and the average power saving rate per PCS is 30.9%. This paper provides a feasible optimization method for improving energy efficiency of manufacturing process, and provides both theoretical and methodological support for the sustainable development of manufacturing industry.

Energy Efficiency Effectiveness of Smart Thermostat Based BEMS

Sat, 17 Oct 2020 00:00:00 +0800

Building Energy Management System (BEMS) is a computer-based system that can control, monitor and optimize the energy consumption of the buildings. To determine the economic feasibility, residential users should know the energy costs associated with the current and the proposed Heating Ventilation and air conditioning (HVAC) system and the implementation costs associated with the installation of the system. The work that is intended here is to develop software that allows the user to observe the estimated energy costs related to a HVAC system after installing a smart thermostat based BEMS. The main factors considered are occupancy of the rooms, weather factor, volume of the room, building envelope and thermostat set point. The software will need some inputs from the user to run the simulation and simulate the energy usage of the HVAC system for one year with a frequency of 30 minutes. This simulation result helps the users to evaluate the economic feasibility of the smart thermostat based BEMS.

Single factor sensitivity analysis of ply parameters to structural properties of wind turbine blade

Lanting Zhang — Sat, 17 Oct 2020 00:00:00 +0800

The ply parameters of composite wind turbine blade have crucial influence on the static strength and stiffness of the blade, factors that are closely related to its performance. The influence degree of different ply parameters on blade performance is also different. In this article, the method of the single-parameter sensitivity analysis is presented. Taking a 1.5 MW wind turbine blade as an object, the load of the blade is calculated and its finite element model is established. According to engineering practice, the investigation range of ply parameters is determined, and the test design scheme of ply parameter for the blade is constructed. The Tsai-Wu failure factor and the maximum displacement for various ply parameters combinations are calculated, and the empirical mathematical models between blade performance and ply parameters are established through polynomial regression analysis method. Furthermore, the sensitivity functions between ply angle, biaxial ply thickness ratio and the blade’s static strength and the static stiffness are established using the single-parameter sensitivity method, and the sensitivity of key parameters on the blade performance is investigated. Finally, the authors provide the changing rule of ply parameter to blade performance and the optimized value for ply angle and biaxial fabric ply thickness ratio. These calculations constitute the method and technology support for the design and optimization of the blade ply structure.

Thermal analysis of the transcritical organic rankine cycle using R1234ze(E)/R134a mixtures as working fluids

Panpan Zhao, Wang Dongdong, Zhou Dao, Zhang Huan, Sun Yun — Sat, 17 Oct 2020 00:00:00 +0800

Abstract: The aim of this work is to research the thermodynamic properties of the transcritical organic rankine cycle system using R1234ze(E) /R134a mixtures as the working fluids for the engine exhaust heat recovery. R1234ze(E) was selected due to its zero ozone depletion potential, relative lower global warming potential and it can remedy the thermodynamic properties of traditional working fluid R134a. The influences of the mass fraction of R1234ze(E) in R1234ze(E)/R134a mixtures, engine exhaust inlet temperature, evaporator temperature on the transcritical organic rankine cycle system performances were analyzed. The results show that the performances of transcritical organic rankine cycle working with R1234ze(E) /R134a mixtures is better than that with pure R134a， but cannot catch up with that working with pure R1234ze(E). When the engine exhaust inlet temperature was a preset value of 250℃, there exists a best expander inlet temperature that is 150℃. Simultaneously, the working system has a highest thermal efficiency and exergy efficiency, 8.78 and 3.03 respectively.

Improvement and experimental study of scroll expander for organic Rankine cycle

Lei Li, Leren Tao, Yanan Gou, Shan Zhang — Sat, 17 Oct 2020 00:00:00 +0800

The scroll expander used in the organic Rankine cycle (ORC) system is improved, and its performance is analyzed experimentally. The modified profile and inlet hole of the scroll expander are enhanced, and the performance of the scroll expander before and after the improvement is analyzed. The results show that when the inlet pressure exceeds 0.7 MPa, the waist-shaped hole with a larger area is preferable. The scroll expander with a waist-shaped hole has a larger output power and wider optimal pressure range. When the inlet pressure is 1.6 MPa, the maximum output power reaches 1260 W, increasing by 230 W. The output power and isentropic efficiency of the scroll expander can be improved by modifying the profile. When the inlet pressure is 1.6 MPa and the rotational speed is 1750 r/min, the maximum output power of the scroll expander is 1235 W, which is 120 W higher than that before the improvement.

EVALUATION OF SMALL WIND TURBINE BLADES WITH UNI-VINYL FOAM ALIGNMENTS USING STATIC STRUCTURAL ANALYSIS

B Venkateshwarlu — Sat, 17 Oct 2020 00:00:00 +0800

Mechanical characteristics of small wind turbine blades of NACA 63-415 series with different Uni-vinyl foam alignments have been evaluated experimentally using Universal Testing Machine and numerically using Finite Element Analysis software ANSYS. The wind turbine blade models considered are selected from US National Advisory Committee for Aeronautics (NACA) 63415 series to give a power output of 1 kW. The blades in this study are made like a sandwich beam structure. The outermost portion of the blade is made of glass fiber reinforced plastics with epoxy resin as composite and Uni-vinyl foam alignments are placed in the inner portion which acts as a stiffener. The alignments used in the blades are rectangular, taper, and teardrop. In FEA analysis, the load is converted into equivalent wind force and applied to the blade structure. Deformation and stress distribution are evaluated at different locations of the blade under different loading conditions. It is observed that the blade with teardrop alignment is having more resistance towards bending compared to blades with other alignments. It is also observed that the taper alignment blade is more capable to sustain higher stresses as compared to the solid and hollow blades.

New correlations for determination of optimum slope angle of solar collectors

Sat, 17 Oct 2020 00:00:00 +0800

The energy coming from solar radiation could be harvested and transformed into electricity through the use of solar-thermal power generation and photovoltaic (PV) power generation. Placement of solar collectors (thermal and photovoltaic) affects the amount of incoming radiation and the absorption rate. In this research, new correlations for finding the monthly optimum slope angle (OSA) on flat-plate collectors are proposed. Twelve equations have been developed to calculate the monthly OSA by the linear regression model, for the northern and the southern hemisphere stations from 15° to 55° and -20° to -45°, respectively. Also, a new method of calculating the yearly tilt angle is developed and compared with several other calculation methods. Results confirm a 20% increase in solar energy absorption by adjusting the collectors' tilt angle in monthly time periods. This is while the adjusted collectors with the yearly optimum slope angle receive approximately 7% higher solar radiation. Furthermore, the proposed equations outperformed the other calculation methods in the literature.

Parameter analysis of CO2 capture with cryogenic anti-sublimation process

Hua Tian, Ke Kang, Lingfeng Shi, Rui Sun — Sat, 17 Oct 2020 00:00:00 +0800

The cryogenic anti-sublimation CO₂ capture technology has attracted the attention of researchers due to its advantages such as no pollution and high product purity. The anti-sublimation process is the core link of this technology, so the study of this process is of great significance to the cryogenic capture system. At present, there are few research works on the CO₂ anti-sublimation process. In order to study the influence of key parameters on the capture performance during CO₂ anti-sublimation, a one-dimensional steady-state of CO₂ anti-sublimation process in a double pipe heat exchanger was established based on the mixture gas of N₂ and CO₂. The effects of cooling nitrogen inlet temperature, mixture gas velocity and pressure on the CO₂ volume fraction, deposition rate distribution, capture rate and valid capture length are investigated. Optimal operation parameters are obtained, which could be used to provide guidance for parameter setting and design of anti-sublimation heat exchanger.

Deep Learning Approach with Optimizatized Hidden-layers Topology for Short-term Wind Power Forecasting

Haichain Shao — Sat, 17 Oct 2020 00:00:00 +0800

Deep learning approach has restricted its generalization ability because of its indigestion hidden-layer information presentation. In particular, recurrent neural networks (RNNs) as one of the representative method of deep learning to deal with time series always bring a challenge issue due to improper analysis of hidden-layer in forecasting modeling. This paper analyzes the hidden-layer information of RNNs by the clustering methods, such as Kmeans, Kmeans++ and Iterative self-organizing data analysis (Isodata) treated as an effective method to divide the similarity of raw data points, and maps the hidden-layer information into the feature space where sample separation is much easier. The architecture of RNNs is therefore optimized since the proper handling of hidden-layer information can directly reduce the risk of over-fitting usually caused by too many neuron nodes, realize the goal of streamlining the number of hidden layer neurons and improve the generalization ability of deep learning. Experiments based on dataset from the National Renewable Energy Laboratory (NREL) is proposed to demonstrate the performance of the proposed approaches, the average forecasting errors of which is respectively increased by 9%, 22% and 24% with respect to 6-steps, 12-steps and 18-steps in four seasons over the ones that achieved using the traditional deep learning approaches.

Seasonal Characteristics Analysis and Uncertainty Measurement for Wind Speed Time Series

Haichain Shao — Sat, 17 Oct 2020 00:00:00 +0800

Wind speed’s distribution nature such as uncertainty and randomness imposes a challenge in high accuracy forecasting. Based on the energy distribution about the extracted amplitude and associated frequency, the uncertainty measurement is processed through a time-frequency Rényi entropy analysis method. Nonparametric statistical method is used to test the randomness in wind speed, more precisely, whether or not the wind speed time series is independent and identically distribution based on the output probability. Seasonal characteristics of wind speed are analyzed based on self-similarity in periodogram under scales range generated by wavelet transformation to reasonably divide the original dataset and effectively reflect the seasonal distribution characteristics. Experimental evaluation based on the dataset from National Renewable Energy Laboratory (NREL) is given to demonstrate the performance of the proposed approach.

Design of a Multichannel Dynamic Temperature Measurement System for Developing Thermal Management System of New Energy Vehicles

Li Wei, Xiong Shusheng, Zhou Xiaojun — Sat, 17 Oct 2020 00:00:00 +0800

A 6-channel temperature measurement system based on labview and PXI modular instrument is described. External analog switches arrays are used to expand the analog input channel of the instrument. The feasibility of the interface circuit for the 3-wire resistance temperature device (RTD) powered by the voltage reference, the filtering algorithm based on moving average filter (MAF) and the data conversion method by direct computation of the polynomial are verified. The results of the comparison test with the commercial temperature measurement instrument clearly shows that each channel has basically the same curve progression with a deviation of less than 1℃. In the range of +20 ℃to +80 ℃, the temperature measurement accuracy is better than ±0.5 ℃, and the sampling rate reaches 1 kHz. The temperature measurement system can be used in the development of new energy vehicle(NEV) thermal management system.

Study on the Online Reforming of Low Concentration Alcohol as Vehicle Fuel

chloe weiss — Sat, 17 Oct 2020 00:00:00 +0800

This research studied catalytic reforming mechanism of low concentration alcohol, analyzed the producing conditions and influencing factors of a mixture of combustible gas, took an analysis towards the composition of the mixture produced by reforming, and studied the respective effects of temperature, traffic, alcohol concentration and catalyst on the components of mixed gas. It is found that, under different working conditions of the engine, the external condition of the reforming reaction changes, and the composition of the reforming gas will differ as well. As a result, the optimum air-fuel ratio of the engine must at the same time adapt to different working conditions.

Solar Thermal Heating and Freeze Concentration for Non-centrifugal Sugar Production

Sat, 17 Oct 2020 00:00:00 +0800

The integration of renewable energy resources in the production of Non-centrifugal Sugar (NCS), known as Jaggery, have been analysed. The work investigates the energy requirements of a system incorporating a freeze-concentrator and a solar thermal heater to reduce the reliance on the combustion of bagasse or other fuels in a Jaggery production process. Depending on the extent to which freeze concentration can be incorporated into the process, results show that the minimum theoretical energy required to produce Jaggery can be reduce by 91.30% overall. Although difficult in practice, this theoretical analysis demonstrates that the integration of freeze concentration close to the eutectic limit of concentration has significant advantages. For optimal configuration and ideal operation of the system the analysis reports a requirement of approximately 3.8 MJ to produce a kilogram of Jaggery from cane juice. When typical process efficiencies (furnace, boiling pan, solar thermal collector, and chiller) are included, the energy required ranged from 4.8 - 5.2 MJ/kg Jaggery. This represents a potential energy saving in excess of 38 MJ/kg Jaggery and a fuel saving of more than 2 kg of bagasse/kg of Jaggery produced.

Experimental Thermal Performance of Different Capillary Structures for Heat Pipes

Wed, 18 Nov 2020 00:00:00 +0800

The temperature control in electronic packaging is the key in numerous applications, looking forward to avoid overheating and hardware failure. Due to high capability of heat transfer, good temperature uniformity, and no power consumption, heat pipes can be widely used for heat dissipation of electronic components. This paper reports an experimental thermal analysis of different capillary structures for heat pipes. The wicks considered are metal screens, axial microgrooves, and sintered metal powder. The heat pipes are made of copper, a 200 mm length tube and a 9.45 mm external diameter. Working fluid used was distilled water. The devices are investigated in three positions: 0°, 90°, and 270° to the horizontal under powers of 5 up to 45W. The results show that in horizontal (0°) and with the evaporator under the condenser (270°), the heat pipes showed similar results. Nevertheless, in the reverse condition (the position against the gravity with the evaporator above the condenser, 90°), the heat pipe with sintered wick presented the best thermal performance, as it has the lowest thermal resistance and supported a higher power. Besides that, the sintered powder capillary structure demonstrates the most homogeneous thermal behavior for every position, making the most suitable for applications susceptible to diverse inclinations.

A Lattice Boltzmann Simulation of Magnetic Field Effect with Different Inclination Angles in Rayleigh-Benard Convection

Wed, 18 Nov 2020 00:00:00 +0800

The magneto-hydrodynamics (MHD) effect is studied at different inclined angles in Rayleigh-Benard (RB) convection inside a rectangular enclosure using the lattice Boltzmann method (LBM). The enclosure is filled with electrically conducting fluids of different characteristics. These characteristics are defined by Prandtl number, Pr. The considered Pr values for this study are 10 and 70. The influence of other dimensionless parameters Rayleigh numbers and Hartmann numbers Ha=0, 10, 25, 50, 100, on fluid flow and heat transfer, are also investigated considering different inclined angles f of magnetic field by analyzing computed local Nusselt numbers and average Nusselt numbers. The results of the study show the undoubted prediction capability of LBM for the current problem. The simulated results demonstrate that the augmentation in heat transfer is directly related to Ra values, but it is opposite while observing the characteristics of Ha values. However, it is also found that f has a significant impact on heat transfer for different fluids. Besides, isotherms are found to be always parallel to the horizontal axis at as conduction overcomes the convection in the heat transfer, but this behaviour is not seen at when. Furthermore, at, oscillatory instability appears but LBM is still able to provide a complete map of this predicted behavior. An appropriate validation with previous numerical studies demonstrates the accuracy of the present approach.

Experimental investigation of flame structure and combustion limit during premixed methane / air jet flame and sidewall interaction

Ying Chen, Jianfeng Pan, Qingbo Lu, Yu Wang, Chenxin Zhang — Wed, 18 Nov 2020 00:00:00 +0800

The effects of inlet gas parameters and sloping sidewall angle on the flame structure and combustion limit with and without sidewall were experimentally investigated. Flame height and impact angle were obtained by chemiluminescence intensity analysis of CH* distribution. First, the combustion characteristics of flame with and without sidewall at different equivalence ratios are explored; then, the influence of Reynolds number and inlet gas temperature on flame structure and combustion limit of v-shaped flame with sidewall are analyzed, and the results with sidewall are compared with those without sidewall. Finally, the variation trend of flame parameters with different sloping sidewall angles is analyzed. The experimental results show that the existence of sidewall makes flame shape change from " M-shaped " to "inverted N-shaped ", and conical shape to trapezoidal shape. The inhibition effect of sidewall on flame stretching downstream is strengthened with the increase in Reynolds number; but as the temperature of the inlet gas increases, the inhibitory effect is obviously weakened. When sloping sidewall angle decreases from 90 ° to 55 ° at 5 ° intervals, flame height and impact angle of v-shaped flame reach the extreme value when β=80°. Compared with the case without sidewall, the range of v-shaped flame with sidewall has no obvious trend of broadening or shrinking when inlet gas temperature is increased; however, as sloping sidewall angle decreases, the range of the v-shaped flame shrinks obviously and flammability limit increases significantly.

Comparative Simulation on Off-design Performance of Gas Turbine Power Units with Alternative Load-control Strategies

Zhiqiang Pan, Zhiwen Lin, Kunle Fan, Cheng Yang, Xiaoqian Ma — Wed, 18 Nov 2020 00:00:00 +0800

Gas turbine power generation units are faced with deep peak-regulation due to the high accommodation of renewable energy in power grids. For this purpose, heavy-duty gas turbine units can operate at various load-regulating strategies fundamentally based on alternative air-fuel ratio and air mass flowrate. To comparatively investigate the part-load performance of gas turbine power units operating at alternative load-regulating strategies, a mathematical model was applied for simulating the off-design performance of the compressor with inlet guide vane (IGV), combustor and turbine. The above three components were modelled respectively by stage-stacking method based on blade average geometric parameter, energy conservation and turbine stage model. Besides, a physical model was built for design and off-design analysis based on GT PRO and THERMOFLEX respectively. The comparative simulation validated the reliability of the results. The influence of the ambient temperature and different load-regulating strategies on the off-design performance of gas turbine power units installed with compressor IGV was studied. The results in the case of a PG 9351FA gas turbine show that the maximum error between the two models is less than 4%; the ambient temperature has a great impact on system performance, i.e. every 5 ℃ increase in the ambient temperature produces a reduction of 3.7% in the relative full-load output and 1.1% in the relative efficiency respectively; when gas turbine operates under constant turbine inlet temperature (TIT), turbine exhaust temperature (TET) starts to rise till it reaches the maximum allowable value. When the load rate is lower than 65%, IGV keeps at a stable minimum angle and both TIT and TET decrease with the load reduction; when gas turbine operates under constant TET within the allowable IGV angle range, TIT drops slightly at load rate of above 60%; while both TIT and TET evidently decreases below 60% load rate operating along the constant corrected speed line at the minimum allowable IGV opening. Gas turbine efficiency is greatly affected by load rate and the performance degradation is more obvious especially in lower load rate regions; Constant TET strategy is superior in the operating efficiency to constant TIT strategy under part-load conditions.

Study on Oil Film Model of EFI Motorcycle Engine Cylinder

Li Wei — Wed, 18 Nov 2020 00:00:00 +0800

Based on the principles of heat transfer, an oil film model in the engine cylinder was established. Under the condition of cold state, the influence of factors such as engine fuel injection, fuel drop point, cylinder inner wall temperature, and inlet fluid on the oil film is comprehensively considered to establish an oil film quality prediction model. Based on the measurement of the compensation oil quantity in the transition conditions, the variation of the oil film during the transition is analyzed. The experimental results show that the velocity of the airflow in the intake port and the temperature and pressure on the wall of the intake port are the main factors affecting the oil film in the cylinder. Based on the above-mentioned experimental and theoretical studies, an oil film distribution model for each cycle of the transition condition was established based on the engine inlet oil film model, and the model is in good agreement with the experimental results.

U Upgrading the Quality of Solid Fuel Made From Nyamplung (Calophyllum inophyllum) Wastes Using Hydrothermal Carbonization Treatment

Pambudi Nugroho Agung — Wed, 18 Nov 2020 00:00:00 +0800

Hydrothermal carbonization (HTC) is a conversion technology of biomass, adopted to obtain solid fuel. This study, therefore, uses HTC to upgrade the Calophyllum inophyllum waste. In addition, the experiment employs variation in temperature of 160°C, 190°C, and 220°C, and holding time of 30 and 60 minutes. Furthermore, the results show that an increase in temperature and holding time causes a decline in the extent of moisture, ash, and volatility, and further increased the carbon content. In addition, the highest calorific value of 4149 cal/gr was produced at a temperature of 220°C, and within 60 minutes of holding time. This was observed to be above the recommendations of the American Standard Testing and Materials (ASTM), with lignite coal at 3500-4611 cal/gr. Therefore, this concludes that HTC enhanced the quality of Calophyllum inophyllum waste used as solid fuel.

Performance Assessment of Heat Exchangers for Process Heat Integration

Fenwicks Shombe Musonye — Fri, 25 Dec 2020 00:00:00 +0800

Pinch Analysis is an attractive solution for thermal energy cost reduction in thermo-chemical industries. In this approach, maximum internally recoverable heat is determined and a heat exchange network is designed to meet the recovery targets. The heat exchanger thermal performance over its lifetime is however a concern to industries. Thermal performance of a heat exchanger is affected by many factors which include the properties of the shell and tube materials, and the chemical properties of the heat transfer fluid. In this study, thermal performance of shell and tube heat exchangers designed to meet heat recovery targets in a Pinch Analysis study is simulated. The aim of this paper is to present predictions of thermal performances of shell and tube heat exchangers with different heat transfer fluids as they undergo fouling degradation and highlight on tube geometrical dimension adjustments required in lieu of considering the fouling factors. Engineering approaches based on thermodynamic analysis, heat balance and Kern Design equations, as well as what if simulation modeling are used in this work. Shell and tube heat exchangers were designed to meet internal heat recovery targets for three process plants, A, B and C. These targets were published in a separate paper. The effects of degradation of the tubes-due to growth of fouling- on thermal performance of the exchanger were simulated using Visual Basic Analysis (VBA). Overall, it was found that growth in fouling reduces thermal efficiency of shell and tube heat exchangers exponentially. An increase in 100 % of fouling factor leads to an average reduction of 0.37 % heat transfer. The Logarithmic mean temperature difference (LMTD) and the ratio of external diameter to internal diameter of the exchanger tubes amplifies the effect of fouling growth on thermal performance of shell and tube heat exchangers. The results of this work can be applied in pinch analysis, during design of heat exchangers to meet the internal heat recovery targets, especially in predicting how fouling growth can affect these targets. This can also be useful in helping operators of shell and tube heat exchangers to determine when to clean the exchangers to avoid heat transfer loss.

Parameter scaling of the aerodynamic breakup of the acoustic levitated droplets in an air jet flow

deng sheng cai, Yanju Wei — Fri, 25 Dec 2020 00:00:00 +0800

The aerodynamic breakup of droplet has been intensely studies, in this paper we aim to establish a unified relationship of dimensionless kinematic parameters such as displacement, spreading diameter, Weber number, time and so on. The breakup characteristics of the acoustic levitated ethanol droplet are experimentally investigated when exposed into an air jet flow. The breakup phenomena was recorded with a high speed camera, the breakup characteristics were analyzed, and the physical models of the moving and transforming behaviors were established to explain the breakup mechanisms. We found that the displacement of the windward side of the droplet follows free acceleration rule, with the displacement, acceleration and time in the dimensionless form. The spreading of the diameter during deformation can also be written in a simple equation as a function of Weber number and displacement. More other details were also discussed.

Demand Response Oriented Market Behavior Decision and Electricity Price Mechanism Design under Low-carbon Energy System

Hongming Yang, Xiao Huang, Ben Niu, Min Qi — Fri, 25 Dec 2020 00:00:00 +0800

智能电网与客户之间的双向互动将在提高绿色和低碳电力行业的整体效率以及实现可再生资源的适当分配方面发挥越来越重要的作用。现有的电价机制与智能电网的技术特征不符；它也无法促进更多最终用户参与电力市场。因此，本文提出了新的模型和方法，以实现市场参与者的最优决策和电价的机制设计，从而可以与智能电网中最终用户的需求响应相兼容。在满足智能电网的技术约束并考虑自身经济利益的同时，将电动汽车和生产者集中在一起。根据可控负荷的需求响应，为零售商提出了实时定价，奖励定价和保险定价的方法，并提出了他们对批发市场的投标决策，以提高可再生能源的渗透水平。面向需求响应的市场行为决策和电价机制设计等关键问题，为低碳能源系统的发展提供了有益的参考。

A An advanced approach for improving the prediction accuracy of natural gas price

quanjia zuo — Fri, 25 Dec 2020 00:00:00 +0800

Natural gas futures as one of the most important commodity futures, its price forecasting is of great significance for hedging and risk aversion. This paper mainly focuses on natural gas futures pricing which considers seasonality fluctuations. In order to study this issue, we propose a modified approach called six-factor model based on the basic three-factor model. Using Monte Carlo method, we first assess and comparative analyze the fitting ability of three-factor model and six-factor model for the out of sample data. It is found that six-factor model has better performance than three-factor model. We then apply the proposed model to predict the price of natural gas futures in the year 2019. It is found that natural gas prices have a weak upward trend in the coming year and are relatively volatile in winter.

An Analysis of the Operation Mechanism of Chemical Industry Park Ecosystem Based on Theory of Ecological Organization

winnie wang — Fri, 25 Dec 2020 00:00:00 +0800

Based on the theory of ecological organization, this paper analyzed the operation mechanism of chemical industry park (CIP) ecosystem by means of dynamic simulation. Research shows that the CIP ecosystem is a complex ecological system whose operation mechanism includes two levels, namely individual enterprises and ecosystem. At the level of individual enterprises, all individual enterprises in the CIP ecosystem have competitive, symbiotic, invasive and other mutual relations, and generate respective operation path. Through interaction and influence, enterprises with different levels of environmental protection achieve long-term equilibrium within the ecosystem. At the level of ecosystem, the CIP ecosystem will make self-organizing and self-adaptive adjustments and changes due to the changes of the external environment in policy, manpower, technology, capital, market, etc. so as to reach the equilibrium state of coordinated operation and stable symbiosis with the external environment.

A Novel Polymorphic Topology with Hybrid Control Strategy based LLC Resonant Converter for Ultra-Wide Input Voltage Range Applications

Yong Shi — Fri, 25 Dec 2020 00:00:00 +0800

Due to realize effective utilization of renewable energy sources, a novel polymorphic topology with hybrid control strategy based LLC resonant converter is analyzed and designed in this paper. By combining the merits of full bridge LLC resonant converter, three-level half bridge LLC resonant converter, and variable frequency control mode, the converter realizes an intelligent estimation of the input voltage with automatically changing its internal circuit topology. Under this control strategy, the different input voltage determines different operation modes. It works in full bridge LLC mode when the input voltage is low. If the input voltage rises to a certain level, it operates in the three-level half bridge LLC mode. These switches are digital and entirely carried out by the DSP (Digital Signal Processor), which means that an auxiliary circuit is not needed, but only modifying the software, and the strategy is simple. Experimental results of a 500W prototype with 100V~600V input voltage and full load efficiency of up to 92% are developed to verify the feasibility and practicability. Thus, the converter is suitable for applications with an ultra-wide input voltage range, such as wind turbines, photovoltaic generators, bioenergy, and other renewable energy sources.

Internet of Things Enabled Intelligent Energy Management and Control System for Heavy Equipment Industrial Park and its Fuzzy Assessment

Jia Zhu — Fri, 25 Dec 2020 00:00:00 +0800

In order to solve the problems of poor information flow, low energy utilization rate and energy consumption data reuse in the heavy equipment industrial park, the Internet of things (IoT) technology is applied to construct the intelligent energy management and control system (IEMCS). The application architecture and function module planning are analyzed and designed. Based on fuzzy group decision and modified TOPSIS by contact vector distance, a fuzzy assessment method for IEMCS scheme alternatives is proposed to achieve scheme selection to ensure the normal subsequent implementation. A case with eight IEMCS scheme alternatives in a heavy equipment industrial park is given for the validation. Through the comparisons with other methods, the reliability of the results obtained by the proposed method is discussed.

Development of environmentally-friendly and energy efficient refrigerant for medium temperature refrigeration systems

piyanut saengsikhiao — Fri, 25 Dec 2020 00:00:00 +0800

This research presents the development of environmentally-friendly and energy efficient refrigerant for medium temperature refrigeration systems that new azeotropic refrigerant mixture of hydrofluorocarbons and hydrocarbon that can retrofit in the refrigeration system using R404A. The medium back pressure refrigeration testing standard that follow CAN/ANSI/AHRI540 standard air-conditioning, heating, and refrigeration institute (AHRI) and The properties of refrigerants and refrigeration simulation system that used national institute of standards and technology (NIST) reference fluid thermodynamic and transport properties database (REFPROP) software and NIST vapor compression cycle model accounting for refrigerant thermodynamic and transport properties (CYCLE_D-HX) software. The methodology uses decision tree function in datamining by rapid minor software that first of KDnuggets annual software poll that showed new azeotropic refrigerant mixture had cooling capacity, refrigerant effect, GWP and boiling point were lower than R404A but work and pressure for medium temperature refrigeration system of azeotropic refrigerant mixture were higher than R404A. The artificial intelligence (AI) by data mining technic can predictive environmentally-friendly and energy efficient refrigerant for medium temperature refrigeration. The result of refrigerant mixed by R134A, R32, R125 and R1270 and is consistent with the evolution of fourth-generation refrigerants that contain a mixture of HFCs and HCs which are required to produce a low-GWP, zero-ozone-depletion-potential (ODP), high-capacity, low-operating-pressure, and nontoxic refrigerant.

Industrial and small-scale biomass dryers: A overview

K Sudhakar — Mon, 22 Mar 2021 00:00:00 +0800

The quality of the drying process depends mainly on the efficient use of thermal energy. Sustainable systems based on solar energy takes a leading role in the drying of agro-products because of low operating cost. However, they are limited in use during off -sun periods. Biomass dryer is one of the simplest ways of drying because of its potential to dry products regardless of time and climate conditions. The other benefit is that crop residues could be used as fuel in these systems. However, the major limitation of the dryer is unequal drying because of poor airflow distribution in the drying medium, which can be improved by integrating some design changes in the dryer. This paper analyzes several designs of industrial and small-scale biomass dryer systems, along with their performance. The study serves as a valuable reference for better implementation of technically feasible and cost-effective biomass dryer.

Life cycle analysis of flat plate solar collectors

Mon, 22 Mar 2021 00:00:00 +0800

In this work, a life cycle analysis is accomplished for flat plate solar collectors. The purpose of this investigation is to predict the sector of overall production that consumes most of the energy and accordingly produces the largest amount of carbon-dioxide. Energy consumption and system efficiency enhancement will be studied and predicted. CES EduPack software is used to perform the analysis of the currently commercial system and the suggested changes to increase the efficiency and make the comparison. Even though cost analysis is done, the priority of selection is given to the most energy conserver and environmentally friendly alternative. However, if the compared alternatives result in the same energy consumption and CO₂ emissions, the cost analysis would be a better approach. It can be stated that solar flat plate collectors are sustainable and renewable energy systems that do not produce CO₂ emissions during their active usage, the processes they undergo during the design contribute to the greenhouse gasses emission.

Transient Free Convection and Heat Transfer in a Partitioned Attic-Shaped Space under Diurnal Thermal Forcing

Suvash Chandra Saha, Ali M Sefidan, Atta Sojoudi, MD Mamun Molla — Mon, 22 Mar 2021 00:00:00 +0800

One primordial consideration in residential ventilation standards is the comfort of provided to people living in those habitations. This is highly dependent on the thermal and fluid flow conditions, the space geometry and so on. Efficient designs may reduce the energy usage, making the buildings more sustainable over a longer period of time. This study aims to investigate the impact of whole day thermal conditions on the fluid flow structure and heat transfer phenomena, mainly natural convection, inside a partitioned attic-shaped configuration. The Finite Volume Method is applied to solve the governing equations. Sinusoidal thermal boundary condition is applied on the sloping walls to illustrate the characteristics of primary flow through daily cycles. A highly thermal conductive partition was placed vertically at the middle of the cavity. Note that through the partition, only heat could freely transfer between two fluid zones. Results show that, during day-time, a stratified fluid flow structure is obtained, which originates from the prevailing conduction heat transfer mechanism, while, for the night-time it changed into a strong convection mechanism which significantly affects the flow structure. These results are particularly important for understanding the fluid dynamics inside the attic shaped building and also designing new residential building.

Research on Operation of Electrothermal Integrated Energy System Including Heat Pump and Thermal Storage Units Based on Capacity Planning

Dingchen Wu — Mon, 22 Mar 2021 00:00:00 +0800

In view of the Three North areas existing wind power absorption and environment pollution problems, the previous scholars have improved the wind abandon problem by adding electrothermal coupling equipment or optimizing power grid operation. In this paper, an electrothermal integrated energy system including heat pump and thermal storage units was proposed. The scheduling model was based on the load data and the output characteristics of power units, each power unit capacity was programmed without constraints, and the proposed scheduling model was compared with the traditional combined heat and power scheduling model. Results showed that the investment and pollutant discharge of the system was reduced respectively. Wind power was fully absorbed. Compared with the traditional thermal power unit, the proportion of the output was significantly decreased by the proposed model. The proposed system could provide a new prospect for wind power absorption and environment protection.

Optimization of combustion characteristics and fuel injection timing of a new type dual-pit combustor rotary engine

Zhongjia Li — Tue, 23 Mar 2021 00:00:00 +0800

In order to improve the performance of the rotary engine, this paper designs a rotary engine with a dual-pit combustion chamber structure, and compares the combustion and emission characteristics with the rotary engine with a traditional combustion chamber. The existence of the dual-pit combustion chamber strengthens the overall vortex intensity in the cylinder, effectively promotes the mixing process of fuel and air in the cylinder, the maximum combustion pressure in the cylinder increased by 8.6%, significantly increases the diffusion combustion speed, and significantly improves the dynamic performance of the rotary engine. On this basis, the effects of fuel injection timing parameters on fuel distribution, combustion and emission characteristics were studied. Fuel distribution is more even and dispersed during injection in the later stage of compression.When the fuel injection timing was 105°BTDC in the middle of the compression phase, the matching effect of fuel distribution law and ignition scheme was the best. When the injection timing was 75°BTDC and 85°BTDC in the late compression stage, the mass fraction of NO_x remained at a low level. The correlation between soot generation and the change of fuel injection timing was weak. When the injection time was 85°BTDC, the soot generation remained at a relatively high level.

Research on Reliability of Desorption Indexes of Drilling Cuttings (K1 and ∆h2): A Case Based on Pingdingshan Mining Region, China

Biao Hu — Tue, 23 Mar 2021 00:00:00 +0800

To accurately predict the risk of coal and gas outburst and evaluate the reliability of desorption indexes of drilling cuttings (K₁ and ∆h₂) in No. 16 coal seam of Pingmei No. 12 coal mine, two sets of coal samples were selected from the target coal seams for proximate analyses, methane adsorption/desorption tests, and desorption indexes of drilling cuttings tests. The results indicated that the desorption volume in the initial stage of desorption is large, and increases slowly in the later stage. The methane desorption volume of PMD1 and PMD2 coal samples accounts for 15.14%–18.09% and 15.72%–18.17% respectively in the first 1 minute, and 43.92%–48.55% and 41.87%–52.25% respectively in the first 10 minutes in the 120-minutes desorption tests. Both K₁ and ∆h₂ present power function relationships with the methane pressure. Similarly, the power function relationships also can be found between the initial desorption characteristics (Q₁ and Q_4-5) and the methane pressure. Finally, the average relative error between measured value and estimated value of the K₁ is less than that of ∆h₂, which indicates that K₁ is a more reliable index than ∆h₂ to predict the risk of coal and gas outburst in the No. 16 coal seam of Pingmei No. 12 coal mine.

Qualitative Comparison between the Brazilian Labeling Program for Buildings and the Portuguese Energy Certification System for Buildings

Tue, 23 Mar 2021 00:00:00 +0800

Buildings represent a significant share of the world's energy consumption, and the sector has drawn the attention of governments, which have adopted policies to reduce energy expenditure. The Certifications of Energy Efficiency in Buildings stand out as one possible solution to achieve this goal, employed in several countries worldwide. The European Union presents advanced energy assessment programs for buildings, being a reference and model for several other regulations in the world. The Energy Certification System for Buildings (SCE) of Portugal is considered a success case, reflected in the significant number of energy certificates issued. The Brazilian Labeling Program for Building (PBE Edifica), first launched in 2009, does not find a broad application today in the Brazilian scenario. This work shows a synthesis of the European Energy Performance of Buildings Directive (EPBD) and the Brazilian and Portuguese regulations' history. A qualitative comparison is made between the SCE and the PBE Edifica to verify a European and a developing country's regulations with a certain degree of cultural and climatic similarities. Through this comparison, proposals are made for improvements to Brazilian certification, seeking to improve its energy planning and energy policy concerning its building stock. The suggestions for improvement presented may also be appropriate for other developing countries that have started and have not yet successfully implemented their energy certification programs in buildings.

Simulation of Electric Field Distribution Along Insulator Surface in Polluted Environments

Yukun Lv, Jiawen Wang, Yuechi Wang, Jing Wang, Jiaxi Yang — Tue, 23 Mar 2021 00:00:00 +0800

In recent years, more than 50% of the cities in the inland area of our country have suffered from moderate pollution. It can affect the distribution of electric field along the surface of insulator and the pollution characteristics of its surface area, even endangers the safe operation of transmission lines. Using the COMSOL software, the simulation of the electric field and pollution accumulation of the XSP-160 porcelain three umbrella insulator was carried out. In view of the medium pollution environment which often occurs in the inland area, the force of the polluted particles deposited on the insulator under of 110kV DC voltage was analyzed. The distribution characteristics of the electric field along the surface in the clean and three kinds of pollution environment (light, medium and heavy) were simulated and compared. The results showed that: 1) In the moderate pollution environment, the pollution particles are greatly affected by the field drag force at the later stage. 2) The electric potential along the surface of each umbrella skirt of the insulator increases non-linearly with the increase of pollution concentration. 3) The pollution particles have obvious influence on the electric field along the low-pressure end umbrella skirt. The maximum distortion rate of the electric potential can reach 220 times.

Research on 48V Super Capacitor Micro Hybrid System with 12V Power Supply Multiplexing Function

Wei Shi, Shusheng Xiong, Wei Li; Bohao Zhang — Tue, 23 Mar 2021 00:00:00 +0800

48V lithium battery micro hybrid system is the most fuel economy vehicle which can be mass produced at present. However, with the irreversible internal resistance increase of the key component 48V lithium battery, and the capacity continues to decline, the system performance deteriorate. Worst case could be the system not functional in the middle and later age of vehicle life cycle. This paper studies the feasibility of using 48V super capacitor as the replacement to 48V lithium battery, and uses a 12V module of 48V super capacitor as the traditional 12V power supply, further reducing the number of components or reducing the demand for parts of 48V micro hybrid system. This paper analyses the 48V super capacitor micro hybrid system scheme, based on which a prototype is built, and carries out the vehicle comparative test, aging test of 48V super capacitor and 48V lithium battery. The results show that: (1) the performance of 48V super capacitor micro hybrid system perform comparably with 48V lithium battery micro hybrid system, and 12V multiplexing function does not cause power loss of super capacitor; (2) The SOC fluctuation of super capacitor is larger than that of lithium battery, but it can satisfied all test conditions through the strategy; (3) the voltage mutation of super capacitor is smaller than that of lithium battery. It can greatly reduce the impact of voltage on vehicle electrical appliances; (4) Through accelerated aging test, the increase of internal resistance and capacity attenuation of super capacitor are better than that of lithium battery. The 48V super capacitor micro hybrid system with 12V multiplexing function is of great significance.

The Non-linear Effect of China's Energy Consumption on Eco-Environment Pollution

chloe weiss — Tue, 23 Mar 2021 00:00:00 +0800

With the increase of total energy consumption, eco-environmental quality drops sharply, which has attracted concerns from all circles. To clarify the influences of energy consumption on the level of eco-environmental pollution has become the top priority of construction of socialist ecological civilization. In this essay, entropy method is adopted to measure the composite indexes of eco-environmental pollution of 30 provinces and cities in China, based on which kernel density function is used to analyze the dynamic law of eco-environmental pollution. And then, traditional fixed effect model and panel quantile regression model are adopted respectively to analyze the influences of energy consumption on eco-environmental pollution. The research finds that composite index of eco-environmental pollution shows N-shaped curve of "rising-dropping-rising" during the sample period, with the overall difference decreasing gradually and the polarization disappearing gradually; in areas with higher eco-environmental pollution, energy consumption has aggravated eco-environmental pollution, while in areas with lower eco-environmental pollution, energy consumption could alleviate eco-environmental pollution to some degree; foreign direct investment could relieve eco-environmental pollution. Therefore, corresponding measures should be taken to improve the quality of eco-environment based on the changes of energy consumption in areas with different eco-environmental pollution.

Design and analysis of a small sewage source heat pump triple supply system

kate Wang — Tue, 23 Mar 2021 00:00:00 +0800

Based on the characteristics of sewage from beauty salons, a simulation model of a small sewage source heat pump triple supply system that can be applied to such places is established to optimize the operating conditions of the system. The results show that with the increase of sewage temperature and flow, the performance of the system also increases. In summer conditions, the system provides cooling, recovers waste heat and condensed heat from sewage, with a COP value of 8.97; in winter conditions, the system heats and produces hot water, with a COP value of 2.44; in transitional seasons, only hot water is produced. The COP value is 2.75. Compared with conventional systems, this system can save energy by 50.9%.

Prediction Model for Gas Outburst Intensity of Coal Mining Face Using Improved PSO and LSSVM

Fuzhong Wang — Tue, 23 Mar 2021 00:00:00 +0800

For the problems of nonlinearity, uncertainty and low prediction accuracy in the

gas outburst prediction of coal mining face, the method of least squares support vector

machine (LSSVM) is proposed to predict the gas outburst, and the mapping model between

the gas outburst and its influencing factors is established. Based on the fact that the regression

accuracy and generalization performance of LSSVM models depend on a proper setting of its

parameters, an improved particle swarm optimization (PSO) algorithm is introduced to search

the parameters automatically. The gas outburst samples from Jiuli Hill Coal Mine in Jiaozuo

City are selected to verify the proposed prediction model. The experimental results show that

the relative errors of the proposed model are not greater than 2.7%, and that the model is

better than both the BP and IGA-LSSVM in prediction accuracy. The improved PSO-LSSVM

model can be used to predict the intensity of gas outburst of coal mining face effectively.

Optimum Calculation of Coal Pillars in Inclined Weathered Oxidation Zone

Shi Chen — Tue, 23 Mar 2021 00:00:00 +0800

Hongyi Coal Mine’s first mining working face 1150401 working face were threatened by weathered oxidation zone which were founded in the west side of the first coal mining working face. The weathered oxidation zone were recharged by Paleogene aquifer which is rich aqueous strong and threat the mining of Hongyi Coal Mine. On the other hand, the water flowing fractured zone of the fist mining working face may connect the Paleogene aquifers. A waterproof pillar should be set between the weathered oxidation zone and the fist mining working face. In order to ensure that waterproof pillar's width not only meets the requirements of resistance the lateral hydro-static pressure from the weathered oxidation zone, but also meets the requirements of ensure that the water flowing fractured zone couldn't connect the Paleogene aquifers. In consideration of the coal seam dip angle, under the premise of a variety of factors crevice belt height, belt rock movement influence, optimization of the first anti-impermeable coal pillar mining face, in order to finalize the waterproof pillar outcome leaving in pillar basis.

Evaluation of Environmental Quality for Abandoned Coal Mine Based on Environmental Vulnerability Index

Peng Qi, yu shang — Tue, 23 Mar 2021 00:00:00 +0800

With the increase of the environment problems of abandoned coal mines, the evaluation significance of environmental vulnerability for those mines was discussed. It established vulnerability evaluation model of abandoned coal mine environment based on multi-factor evaluation, and proposed to rank criteria of nine factors index. Then it formulated the evaluation process. Finally, evaluation hierarchies’ criterion of environmental vulnerability evaluation for the abandoned coal mines was established.

Progress on Heat Transfer of Hot Dry Rock Enhanced Geothermal System

Wed, 02 Jun 2021 00:00:00 +0800

Hot Dry Rock (HDR) is the most potential renewable geothermal energy in the future. Enhanced Geothermal System (EGS) is the most effective method for the development and utilization of HDR resources. Due to the particularity of the mathematical models of heat transfer, research in this field has been at an exploratory stage, and its methods are mainly experimental tests and numerical simulations. This paper introduces the research progress of the mathematical models of heat transfer of Hot Dry Rock EGS in detail at home and abroad, makes a comparative analysis of various research results, summarizes their advantages and disadvantages, and draws the following conclusions: The relevant scholars should study the mathematical models of heat transfer of multiple parallel fractures, single irregular curve fracture or multiple branches fractures of HDR on the basis of experiment and numerical simulation of the model of single fracture and crossed fractures of HDR. The unsteady heat transfer process among the multi-fractures of HDR should be studied in depth based on the results of the three-dimensional models. The complex three-dimensional mathematical models of heat transfer of Hot Dry Rock EGS should be studied deeply considering the anisotropy of rock masses.

Application of Superhydrophobic Surface on Boiling Heat Transfer Characteristics of Nanofluids

Cong Qi, Yuxing Wang, Zi Ding, Jianglin Tu, Mengxin Zhu — Wed, 02 Jun 2021 00:00:00 +0800

Boiling heat transfer is a mode using the phase change of working medium to strengthen the heat exchange due to its good heat exchange capability, and it is widely used in heat exchange engineering. Nanofluids have been used in the direction of enhanced heat transfer for their superior thermophysical property. The wetting, spreading and ripple phenomena of superhydrophobic surfaces widely exist in nature and daily life. It has great application value for engineering technology. In this article, the boiling heat exchange characteristics of nanofluids on superhydrophobic surface are numerically studied. It was found that with the increase of superheating degree, the steam volume ratio of unmodified heated surface increases to saturation, while the steam volume and evaporation ratio of modified superhydrophobic surface increase firstly and then decrease. At the same time, bubbles are generated and accumulated more fully on superhydrophobic surface. It was also found that nanofluids with low viscosity are more affected by superhydrophobic surface characteristics, and the increase is more significant with high superheating degree, and the superhydrophobic surface is beneficial to enhancing boiling heat exchange. Compared with the simulation results, it could be concluded that the boiling heat exchange performance of CuO-water nanofluids on the modified superhydrophobic surface is better than that of CuO-ethylene glycol nanofluids under high superheating degree.

Performance Of Desiccant-Based Cooling Systems In Hot-Humid Climates: A Review

Maatouk Khoukhi, Omar Al Khatib — Wed, 02 Jun 2021 00:00:00 +0800

This paper reviews the principle and application of the thermally activated desiccant cooling systems with their capability to perform efficiently in hot-humid climates of the Middle East. The paper first introduces the continuous increase of thermal comfort required in building and their relation with the consumption of conventional energy sources. The importance of desiccant cooling technology and its applications has been introduced as well. The energy and environmental issues with the conventional energy supply and the demand with the environmental problems and conditions mainly related to indoor air quality have been also discussed in the second chapter of this paper. The third part of this paper deals with different techniques and systems applied for cooling and dehumidification including the principles of solid and liquid desiccant applications. Indeed, these systems have high potential in terms of thermal performance and efficiency if well applied particularly in hot and humid climates. The result of a case study of the solid desiccant cooling system combined with solar energy for the desiccant wheel regeneration has been presented in the last chapter in this paper to show the capability of these systems once well applied in a hot-humid climate.

Multi-scale superhydrophobic anti-icing coating for wind turbine blades

Wed, 02 Jun 2021 00:00:00 +0800

As a surface functional material, super-hydrophobic coating has great application potential in wind turbine blade anti-icing, self-cleaning and drag reduction.In this study, we proposed a simple preparation process to prepare a new type of superhydrophobic coating. The embedding method is used to directly construct a superhydrophobic coating with a mechanically flexible ZnO/SiO2 multi-scale micro-nano structure. The prepared coating has a higher static water contact angle (153°) and a lower rolling angle (3.3°). More importantly, due to the synergy of the mechanical properties provided by SiO2 and the micro-nano structure of the nano-particle, the coating has excellent mechanical durability. What's more noteworthy is that the coating also shows good self-cleaning and anti-icing properties. This research provides a theoretical reference for the preparation of a mechanically stable coating with a simple preparation process, as well as a basic research on the anti-icing behavior of the coating.

Impact of Demographic Transition on household energy consumption: A case from China

Dequn Zhou, Xinyi Gu, Hao Ding — Wed, 02 Jun 2021 00:00:00 +0800

Aging population and low fertility, two key concerns during the demographic transition, have great influences on household energy consumption. Understanding their impacts on household energy consumption is important for predicting future energy consumption and reaching effective policies. This paper studies the impacts of demographic transition on household energy consumption based on panel data of 30 provinces in China from 2005 to 2016. Child-age dependency rate (CDR) and old-age dependency rate (ODR) are selected to track the shifts in age structure. They are introduced into a STIRPAT model to measure their impacts on household energy consumption. Both static and dynamic models are implied to compare their differences. Besides, 8 representative regions are additionally investigated to find some regional characteristics. The results show that the current demographic transition to aging population expands household energy consumption. The aging population and low fertility cause additional difficulties for energy saving and emission reduction. Household energy consumption in less developed areas are more likely to be affected by CDR and ODR. Regions with large population are also more easily influenced by demographic tansitions especially CDR. It indicates that policy interventions in demographic transition and continuous optimization of household energy consumption structures according to the population dynamics are necessary.

Impact of Electricity Shortages on Productivity

Zhongcheng Wang, Xinhong Xue — Wed, 02 Jun 2021 00:00:00 +0800

Electricity plays an important role in industrialization and growth. Unreliable electricity supply will affect firms’ investment and production. This paper uses data of Chinese manufacturing firms to explore how firms response to electricity shortages and the impact on productivity. In general, self-generation of electricity and investment in Research and Development (R&D) have significant positive relationship with electricity shortages. Further investigation reveals that self-generation brings about labor productivity losses. Investment in Research and Development can promote productivity, but cannot offset the negative impact of electricity shortages on labor productivity. The responses and their effects on productivity vary among firms of different sizes. Large firms are more likely to investment in R&D. Only in medium-sized firms can R&D investment reduce productivity losses through R&D investment. Large firms also suffer significant productivity losses due to self-generation of electricity. The findings reveal that policy-makers and firms should put greater efforts on technologies and reliable electricity supply.

Will Coal Price Fluctuations Affect Renewable Energy Substitution? A Computable General Equilibrium-Based Study of China

Yibo Yin, Wenhui Zhao, Lu Mao; Konglu Zhong, Guanghui Yuan; Hai Huang — Wed, 02 Jun 2021 00:00:00 +0800

Changes in the energy price system will determine the direction of evolution of the energy industry structure. As a country where coal is the dominant energy source, what is the effect of coal price fluctuations on China’s industry development costs and energy consumption structure? To investigate this problem, this paper utilized an economy–energy–environment computable general equilibrium model. In this study, four aspects were analyzed: energy supply side, proportion of renewable energy consumption, macroeconomy, and changes in CO₂ emissions. The results of this study show that an increase of 10%–20% in coal prices contributes to a shift into using renewable energy, which leads to energy saving and emission reduction. Renewable energy and clean energy rose by 0.57%–4.47% in the energy structure, but this has a certain negative impact on the macroeconomy. The gross domestic product (GDP) fell by 0.07%–0.18%. As a result, the decline in coal prices became an obstacle to renewable energy substitution and energy conservation. In addition, we put forward policy suggestions according to the results in energy, economic, and environmental effects.

Analysis of Driving Factors of Natural Gas Consumption in China: Based on Regional Integration and LMDI Method

Huiwen Xu, Zhen Wang — Wed, 02 Jun 2021 00:00:00 +0800

China is now at the stage of rapid development in the natural gas industry. Driven by regional economic integration, a regional natural gas market composed of neighboring provinces has gradually come into being, which leads to consistency in terms of policy formulation, resource coordination, facility construction, and market expansion. This paper attempts to conduct a horizontal comparative analysis of the economic level, natural gas consumption characteristics and natural gas pipeline network density of three regions with obvious integration characteristics in China. In addition, the paper adopts the method of Logarithmic Mean Divisia Index (LMDI), and applies four core indicators, namely economic growth effect, energy intensity effect, energy structure effect, and substitution effect. On this basis, it means to explore the contribution of different indicators in various regions to the growth of natural gas consumption. According to the research results, it can be concluded that driving factors of natural gas consumption differ significantly in various regions. In places with a more developed economy, the energy substitution effect contributes greater to natural gas consumption; while the economic growth effect contributes less. Moreover, different regions show slight discrepancy in the contribution of energy intensity, and the energy structure contributes the least. All these conclusions further explain the current differences in China’s natural gas consumption characteristics and their reasons.

An intelligent diagnosis method of working conditions in sucker-rod pump well based on convolutional neural network and transfer learning

Ruichao Zhang, Liqiang Wang, Dechun Chen — Wed, 02 Jun 2021 00:00:00 +0800

In recent years, the deep learning model represented by convolutional neural network has shown incomparable advantages in image recognition, and has been widely used in various fields. In the diagnosis of sucker-rod pump working condition, due to the lack of large-scale dynamometer card data set, the advantages of deep convolutional neural network are not well reflected, so its application is limited. Therefore, this paper proposes an intelligent diagnosis method of working conditions in sucker-rod pump well based on transfer learning, which is used to solve the problem of few samples in dynamometer card data set. Based on the dynamometer diagrams measured in the oilfield, image classification and preprocessing are carried out, and the dynamometer diagram data set including 10 typical working conditions is created. On this basis, with the help of the trained deep convolutional neural network learning model, the model training and parameter optimization are carried out, and the learned deep dynamometer diagram features are transferred and applied, so as to realize the intelligent diagnosis of indicator diagram. The experimental results show that the transfer learning is feasible, and the performance of deep convolutional neural network is better than that of shallow convolutional neural network and general fully connected neural network. It can effectively and accurately diagnose the working conditions of sucker-rod pump well, and provides an effective way and method to solve the problem of few samples in dynamometer card data set.

Position Sensorless Control System of Permanent Magnet Synchronous Linear Motor Based on Sliding Mode Observer with an Improved Phase-locked Loop

Feng YU — Wed, 02 Jun 2021 00:00:00 +0800

In this paper, position sensorless control system of permanent magnet synchronous linear motor (PMSLM) based on sliding mode observer (SMO) with an improved phase-locked loop (PLL) is studied. Firstly, according to the mathematical model, a SMO is designed for sensorless control PMSLM drive. Thereafter, an improved PLL is proposed to tackle the imperfection of data overflow existed in the traditional PLL. The designed SMO incorporating with the improved PLL can be effectively suppress the pulsation of the estimated position and hence the chattering of the derived electrical angular velocity. At last, simulated and experimental results are presented to verify the effectiveness and feasibility of the position sensorless control system.

Technical system construction in the market trading system on demand response in the Energy Internet environment

yinhe bu — Wed, 02 Jun 2021 00:00:00 +0800

With the rapid development of the economy and society and the explosive growth of new energy generation, the balance between the supply and demand of power grid is faced with new challenges. Information and communication technology promotes the deep integration of Internet technology and the energy industry. Therefore, the Energy Internet has emerged as required and has become a new focus and mode of market-oriented development and friendly economic operation in the field of demand response. Based on the technical architecture of the Energy Internet platform and combined with the design concept of the Cyber-Physical Systems (CPS) architecture, this paper constructs the technical system of the "end-side-net-cloud" four-hierarchy demand response system, including user resource management, transaction strategy issuance, and response process monitoring. Through integration of "Internet +" thinking, this paper innovates the interactive mode to allow users to participate in demand response, forms a market-oriented adjustable load participation mechanism for grid operation, and realizes coordinated interaction of "supply-network-load-storage", thereby effectively alleviating the tension between power supply and demand in some regions, promoting new energy consumption, and ensuring the safety and economy of grid operation.

Wind Power Revenue Potential - High Frequency Simulation for Finland

Sakarias Paaso, Ali Khosravi, Postdoctoral Researcher — Wed, 02 Jun 2021 00:00:00 +0800

Potential revenue from wind power generation is an important factor to be considered when planning a wind power investment. In the future, that may become even more important because it is known that wind power generation tends to push electricity wholesale prices lower. Consequently, it is possible that if a region has plenty of installed wind power capacity, revenue per generated unit of electricity is lower there than could be assumed by looking at the mean electricity wholesale price. In this paper, we compare 17 different locations in Finland in terms of revenue from wind power generation. That is done by simulating hourly generation with three different turbine types at two different hub heights and multiplying that by the hourly electricity spot price for years 2018 and 2019. Estimated revenues differ greatly between locations and turbine types, major factor being technical potential, i.e. the amount of electricity generated. Differences between revenues per generated MWh seem to be small, however, the smallest figures being on the western coast where installed capacities are also the largest in Finland.

Structure and Combustion Characteristics of Methane/Air Premixed Flame Under the Action of Wall

Feiyang Li — Wed, 02 Jun 2021 00:00:00 +0800

In order to obtain the combustion characteristics of the CH₄/Air premixed flame under the action of the wall, a study on the impact of the jet flame on the wall at different separation distances was carried out. The separation distance from the burner outlet to the lower surface of the wall is changed and the flame structure is obtained through experiments. The temperature, velocity and reaction rate are obtained through numerical simulation, and the law of flame characteristics change is obtained through analysis. The results show that as the separation distance increases, the premixing cone inside the flame gradually changes from a horn to a complete cone and the length of the premixing cone profile increases. The temperature peak and velocity peak of the mixture in the axial direction gradually increase, and the temperature and velocity in the radial direction first increase and then decrease. The gradient of temperature and velocity reach the maximum when the separation distance is 11mm. The net reaction rate peaks of reactants (CH₄), intermediate products (CO) and products (CO₂, H₂O) on the axis and the axial distance corresponding to the peaks increase accordingly. The chemical reaction rate near the wall also gradually decreases with the increase of the separation distance.

The Method of the SiC MOSFET replacing the Si IGBT in the Traditional Power Electronics Converter without Redesigning the Main Circuit and the Driver Circuit

Lei Zhang, Dejian Yang, Lei Ren, Yun Cheng, Qiufeng Yan, Yinlong Yuan — Wed, 02 Jun 2021 00:00:00 +0800

As a wide bandgap power electronics device, the SiC MOSFET has the advantages that the traditional Si IGBT cannot reach. Using the SiC MOSFET to replace the Si IGBT in the existing power electronics converter is an effective measure to improve the performance of the power electronics circuit and to promote the upgrading of the converter. Generally, in order to maximize the advantages of the SiC MOSFET, the Si IGBT in the traditional power electronics circuit cannot be simply replaced by the SiC MOSFET, but the main circuit and the driver circuit need to be redesigned because the oscillation problem and the cross-talk problem caused by the parasitic parameter is very serious when the SiC MOSFET switches. However, due to the requirements of the equipment development cost and cycle, it is often difficult to redesign the circuit hardware structure of all converters. In order to solve this contradiction, the ferrite bead is inserted into the main circuit at a certain position in this paper. Without redesigning the hardware structure of the main circuit and the driver circuit, the SiC MOSFET can replace the Si-based power electronics device directly, and the loss can be reduced with small oscillation. Finally, the effectiveness of the method is proved by experiments.

Application of Model Predictive Control Based on Kalman Filter in Solar Collector Field of Solar Thermal Power Generation

Xiaojuan Lu, Zeping Liang — Wed, 02 Jun 2021 00:00:00 +0800

There are two prominent features in the process of temperature control in solar collertor field. First, the dynamic model of solar collertor field is nonlinear and complex, which needs to be simplified. Secondly, there are a lot of random and uncontrollable measurable and unmeasurable disturbances in solar collertor field. This paper uses Taylor formula and difference approximation method to design a dynamic matrix predictive control (DMC) by linearizing and discretizing the dynamic model of the solar collector field. In addition，the purpose of controlling the stability of the outlet solar field salt temperature is achieved by adjusting the mass flow of molten salt.In order to further improve the system's ability to suppress unmeasured disturbances , a steady-state Kalman filter is designed to estimate state variables, so that the system has better stability and robustness.The simulation verification results show that the DMC control system based on Kamlan filtering has better control effect than the traditional DMC control system. The DMC control system based on Kamlan filtering reduces the overshoot of the system by 4%, and its robustness is stronger.

Effect of NCZ Thickness on Thermal Efficiency of Salt Gradient Solar Ponds

Nan Li — Wed, 02 Jun 2021 00:00:00 +0800

Current models for solar ponds are no accurate for estimating radiation transmission or thermal efficiency. Here, we combine the Hull Model and Wang and Seyed-Yagoobi Model to establish an improved radiation transmission model and a thermal efficiency model. The new models are more accurate to actual measured conditions because multiple reflections and turbidity effects are included. Absorption penetration, thermal conductivity loss and thermal efficiency are numerically analyzed and thoroughly discussed. ΔT/I₀ plays a critical role for the thermal efficiency of solar pond. Furthermore, it was found through calculation that there is an optimum thickness of the NCZ. When the thickness of the NCZ is greater than this critical threshold, the amount of solar energy that is able to reach and is absorbed by the LCZ is reduced by the NCZ, and both temperature and thermal efficiency are decreased in the pond. In addition, NCZ thickness is also related to the temperature, turbidity, salinity variation and bottom reflectivity.

Operation strategy analysis and configuration optimization of solar CCHP system

Duojin Fan, Chengji Shi, Kai Sun, Xiaojuan Lu — Wed, 02 Jun 2021 00:00:00 +0800

This paper proposed a new type of combined cooling heating and power (CCHP) system, including the parabolic trough solar thermal (PTST) power generation and gas turbine power generation. The thermal energy storage subsystem in the PTST unit provides both thermal energy and electrical energy. Based on the life cycle method, the configuration optimization under eight operation strategies is studied with economy, energy, and environment indicators. The eight operation strategies include FEL, FEL-EC, FEL-TES, FEL-TES&EC, FTL, FTL-EC, FTL-TES, and FTL-TES&EC. The feasibility of each strategy is verified by taking a residential building cluster as an example. The indicators under the optimal configuration of each strategy are compared with that of the separate production (SP) system. The results show that the PTST-CCHP system improves the environment and energy performance by changing the ratio of thermal energy and electric energy. The environment and energy indicators of FEL-TES&EC are superior to those of FTL-TES&EC in summer, and the results are just the opposite in winter. The initial annual investment of the PTST-CCHP system is higher than that of the SP system, but its economic performance is better than that of the SP system with the increase of life-cycle.

Development of Advanced Biomass Cookstove and Performance Comparisons using the Modified Star Rating Methodology

S K TYAGI, Prof., Himanshu Himanshu, Kunwar Pal, Dr., Sanjeev Jain — Sat, 17 Jul 2021 00:00:00 +0800

A disruptive approach to a fundamental process has been applied in a biomass combustion device with two variable speed fans to supply air for gasification and another for combustion processes, separately. Further, the preheating of secondary air, required for combustion process was also ensured through annulus chamber before being fed into the combustion chamber. The turbulent flow and homogenous mixing were also ensured by controlling the flow rate resulting in the reduced emissions of carbon monoxide (CO) and fine particulate matter (PM 2.5, particulate matter having aerodynamic diameter <2.5 micron). The design approach applied here has also ensured the homogeneous mixing of preheated air with the volatiles, resulted in cleaner combustion. This arrangement has led to the emissions of PM2.5 and CO much better than those of the earlier cookstove models, and very close to that of a liquefied petroleum gas (LPG) stove. Implemented on a national scale, this could correspond to a reduction of CO2 by ~10% from all emissions.

An experimental study on oxidized mercury adsorption by bromide-blended coal combustion fly ash

Sat, 17 Jul 2021 00:00:00 +0800

The application of forced mercury oxidation technology would lead to an increase of Hg²⁺ concentration in the flue gas. Although Hg²⁺ can be removed in the WFGD, the mercury re-emission in the WFGD can increase the total removal of mercury from coal-fired power plants. Hence, it is necessary to remove Hg²⁺ in the devices before the WFGD. Fly ash adsorbent is considered as a potential alternative for commercial activated carbon adsorbent. However, the adsorption efficiency of the original fly ash is low, modification procedure is needed to enhance the adsorption performance. In this study, the adsorption of brominated fly ash on Hg²⁺ was studied obtained from the bromide-blended coal combustion technology. The brominated fly ash exhibited excellent performance for Hg²⁺ adsorption. The HBr and SO₂ in flue gas could improve adsorbent’s performance, while HCl would hinder its adsorption process. Also, it was demonstrated by Hg-TPD experiments that the adsorbed Hg²⁺ mainly existed on the fly ash surface in the form of HgBr₂. In summary, the brominated fly ash has a broad application prospect for mercury control.

Improving Functionality of 2DOF Piezoelectric Cantilever for Broadband Vibration Energy Harvesting Using Magnets

chloe weiss — Sat, 17 Jul 2021 00:00:00 +0800

This paper presented a 2DOF nonlinear piezoelectric energy harvester for improving the efficiency of energy harvesting in low frequency range. The device consisted an L-shaped piezoelectric cantilever with a magnet at the tip of the first beam and two external magnets on the pedestal. The distance between the magnets which generated nonlinear magnetic attraction was adjusted such that the system can exhibit monostable or bistable characteristics. First, the model of this piezoelectric energy harvester was established and the dynamic equation was derived based on the magnetic attractive force. Then, the nonlinear dynamic responses of the system subject to harmonic excitation were explored by a numerical method and validated by experiments. At an excitation level of 4 m/s2 in reverse sweep test for the proposed nonlinear harvester, nearly 240% increase in frequency bandwidth was obtained compared to 2DOF linear one in the first two resonance regions under both monostable and bistable state. Moreover, the nonlinear device yielded a closer frequency band gap between the first two resonance regions. The findings provide insight for the design of a broadband energy harvester when there is nonlinearity using magnets.

Evaluation for Regional Differences and Convergence on Electricity Productivity: A case of China

Pinjie Xie, Ying Zhai, Fan Yang, Zhuowen Mu — Sat, 17 Jul 2021 00:00:00 +0800

Energy and environment issues have elicited extensive attention, given that China has entered a “New Normal” of economic development. In fact, accurately evaluating the difference and convergence characteristics of the electricity productivity and enhancing electricity productivity in an all-round way is critical to achieve economic growth and energy saving. The Gini coefficient, Theil index, and Mean log deviation are utilized to measure regional differences in China’s electricity productivity from 1997 to 2016 in five regions, and conditional β convergence is empirically analyzed with the spatial Durbin model. Results show that first, China’s electricity productivity is improving. The overall feature is that the east has a higher efficiency than the west. Second, the difference in electricity productivity is the smallest in the northeast and the largest in the northwest. The overall difference has been exhibiting maintained growth since 2014, and its growth rate has been slowing down. Meanwhile, inter regional difference plays an important role and gradually dominates. Lastly, the electricity productivity in China exhibits beta convergence, except for the northwest. It can be improved by gross domestic product and research and development expenditure. Moreover, the spatial spillover effect exists. Spatial spillover must be considered fully to build regional cooperation mechanisms, further reduce the regional gap, and improve regional electricity productivity.

Optimal Trading Decision Making of Power Supply Chain under Renewable Portfolio Standards

Xu HaoCheng, Wang Hui, Zhao WenHui — Sat, 17 Jul 2021 00:00:00 +0800

Under a background of the implementation of the renewable portfolio standardsand the ever-improving tradable green certificate scheme, the increasing environment-friendly preference of power users is leading to changes in electricity demand, which, in turn, is driving changes in the decision-making behaviors of various actors in the power supply chain. Based on this, with the goal of maximum profit, consumer power demand functions have been introduced with some consideration of the factors of consumer preference to establish an optimal profit model for each trading subject in the non-cooperative state of the power supply chain, under the constraints of meeting the renewable energy portfolio standards. Here, the optimal strategy of each trading subject is presented through adopting the reverse induction method. Furthermore, examples are used to analyze factors such as the influence of environmental protection preferences, quota ratios, price substitutions, and market demand as well as the optimal profit of each trading subject in view of providing a reference for the decision making in the power supply chain trading subjects.

The relationship between urbanization and domestic energy consumption：An empirical study of Shandong Province, China

chloe weiss — Sat, 17 Jul 2021 00:00:00 +0800

The rapid development of urbanization has led to a swift increase in total energy consumption, while the transformation of residents’ lifestyles has led to changes in the types of energy used in daily life and an increase in consumption. The level of urbanization varies greatly in different regions, and this difference causes disparities in living energy consumption. Therefore, it is necessary to study the impact of urbanization development on domestic energy consumption from the regional level on the basis of local actual conditions. Through field investigations and questionnaires, this study systematically examines the current situation and changing trends of domestic energy consumption in Shandong Province and applies a time series econometric model to analyze empirically the relationship between urbanization rate and total domestic energy consumption. Research results show that the total domestic energy consumption and urbanization rate of Shandong are generally increasing. A long-term stable and balanced relationship exists between the level of urbanization development and domestic energy consumption. The improvement of urbanization level can promote the increase of domestic energy consumption. There is little difference in the average total energy consumption of urban and rural residents. The total energy consumption per capita of urban residents is 380.22 kilograms of standard coal while that of rural residents is 367.97 kilograms of standard coal. Each time the urbanization rate increases by 1 percentage point, the domestic energy consumption increases by approximately 795,200 tons of standard coal.

Maximizing the Benefit of Rate Transient Analysis for Gas Condensate Reservoirs

Ahmed Mohamed Farag, Mahmoud Tantawy, Ahmed El-Gibaly — Sat, 17 Jul 2021 00:00:00 +0800

In recent years, many trials have been made to use the Rate Transient Analysis (RTA) techniques as a method to describe the gas condensate reservoirs. The problem with using these techniques is the multi-phase behavior of the gas condensate reservoirs. Therefore, the Pressure Transient Analysis (PTA) is commonly used in this case to analyze the reservoir parameters. In this paper, we are going to compare the results of both PTA and RTA of three wells in gas condensate reservoirs. The comparison showed a great match between the results of the two mentioned techniques for the first time using a reference GOR of 75,000 SCF/STB. Therefore, we came to the fact that we can depend on RTA instead of PTA in order to spare the cost associated with the PTA in the gas condensate reservoirs.

The Using the Taguchi Method and Grey Relational Analysis to Optimize the Performance of a Solar Air Heater

Manar Bahjat AL Hajji — Sat, 17 Jul 2021 00:00:00 +0800

Solar energy is regarded as one of the promising renewable energy sources in the world. This study aims to validate the thermal performance of a Solar Air Heater (SAH). A typical Grey-Taguchi method was applied. The Orthogonal Array (OA), Signal-to-Noise ratio(S/N), Grey Relational Grade (GRG) ، and Analysis of Variance (ANOVA) were employed to investigate the performance characteristics of (SAH). Experimental observations were made in agreement with Jordanian climate 31˚00ﹶ N latitude and 36˚00ﹶE longitude with a solar intensity of 500 W\m2. The Process operating factors selected for optimization are the tilt angle with three levels (0˚, 22˚, 45˚), inlet velocity with two levels (1.2 m\s, 1.8 m\s), and absorber plate material with two levels (Aluminum, wood). In this study, the Grey-Taguchi approach is validated by performing 12 individual experiments (L12). The results show that the process factors sequence required for a maximum SAH efficiency (SAH µ) is V > T > M. Using this approach, we combined the OA design of L12 experiment with Grey Relational Analysis(GRA). As a result of that, the level of each operating conditions which optimizes both process responses (Temperature difference, ∆T and Solar air heater efficiency, SAH µ) can be specified with a minimum number of tests compared with classic GRA. The optimal operating conditions of a SAH for multiple performance characteristics are determined as T2, M2, and V2 respectively, which are in congruence with the experimental results.

Study of polymer flooding in heterogeneous porous media by using nuclear magnetic resonance

Xing Zhang — Sat, 17 Jul 2021 00:00:00 +0800

Polymer has been successfully used to enhance crude oil recovery of water flooding. However, the application of polymer flooding is limited by the heterogeneity of reservoir. In this work, the role of polymer flooding in heterogeneous reservoir was explored by nuclear magnetic resonance (NMR) spectroscopy. Parallel core displacement experiments were carried out to study polymer flooding in high permeability formation. The results showed that the polymer flooding area was related to permeability and pore connectivity. At the end of the water flooding stage, the residual oil was not evenly distributed within the porous media. The percent crude oil recovery increased with the increase in the pore diameter. Crude oil recovery from larger pore sand packs was higher, and water broke through the highly permeable core first. At 0.3 PV polymer injection, the water mobility of the high permeability sand pack decreased. Polymer injection appeared to a dual effect, an oil displacement effect and a traction effect. The oil displacement effect was responsible for driving out the crude oil in large pore, whereas the traction effect was responsible for driving out residual from small pores. At 1 PV polymer injection, the polymer solution channeled through the highly permeable sand pack rapidly. The crude oil in the macro pores was washed out completely. The NMR water-phase spectrum line of the highly permeable sand pack was much higher than that of the low permeability sand pack. Under different core permeability and porosity, the NMR peak of the crude oil-phase spectrum line indicated that the polymer flooding is mainly effective on pores > 40 microns.

Aging characteristics of XLPE insulation of 110kV cables in the initial stage of operation

Jie Chen, Wei Zhang, Man Ding, Libin Hu, Jinpeng Wang, Chenying Li, Jingying Cao — Sat, 17 Jul 2021 00:00:00 +0800

in this paper, the electrical and physicochemical characteristics of the XLPE insulation of cables in the initial stage of operation are studied, and the degradation characteristic of the XLPE insulation material under multiple stress during operation is analyzed. The dielectric constant and loss characteristic of the XLPE film is derived from the broadband dielectric spectroscopy from 10^-1Hz to 10⁶Hz, and the morphological structure of the XLPE film is determined from the differential scanning calorimetry method and X-ray diffraction method, and the AC breakdown characteristic of the dielectric film is also studied. From the experiment, the crystallinity of XLPE insulation reaches its maximum in 3 ~ 4 years of operation, and then decreases gradually with the increase of service life; the XLPE insulation breakdown strength of the operated cables is higher than that of new cables; and the measurement results of broadband dielectric spectrum are consistent with those of physicochemical analysis and breakdown experiments.

Experiment Investigation of Organic Rankine Cycle (ORC) for Low Temperature Geothermal Fluid: Effect of Pump Rotation and R-134 Working Fluid in Scroll-Expander

Nugroho Agung Pambudi, Santiko Wibowo, Ranto Ranto, Lip Huat Saw — Mon, 26 Jul 2021 00:00:00 +0800

Organic Rankine Cycle (ORC) is one of the solutions to utilize a low temperature geothermal fluid for power generation. The ORC system can be placed at the exit of the separator to extract energy from brine. Furthermore, one of the main components of the system and very important is the pump. Therefore, in this research, the pump rotation is examined to investigate the effect on power output and energy efficiency for low temperature geothermal fluid. The rotation is determined by using an inverter at the frequency of 7.5 Hz, 10 Hz, 12.5 Hz, 15 Hz, and 17.5 Hz. R-134 working fluid is employed with 100oC evaporator temperature related to low temperature of geothermal fluid. Furthermore, the condenser temperature and fluid pressure were setup to 20oC and 5 bar. The results showed that there is an increase in mass flow rate, enthalpy and generator power output along with increasing pump rotation. The maximum generator output power is 377.31 W at the highest pump rotation with 17.5 Hz frequency.

The Effect of Injected Air Bubble Size on the Thermal Performance of a Vertical Shell and helical Coiled Tube Heat Exchanger

Hameed Balassim Mahood, Saif S Hasan, Mr, Ali Sh Baqir, Prof. — Fri, 17 Sep 2021 00:00:00 +0800

The effect of injecting air bubble size on the thermal performance of a vertical counter-current shell and coiled tube heat exchanger is carried out experimentally. The experiments were accomplished in a cylindrical shape heat exchanger with size of 50 cm height and 15 cm diameter. Copper coil with 4 m equivalent length and 0.6 cm dimeter was used to carry the hot fluid (water). Four different cold fluid flow rates (shell side, Qs = 2,4,6 and 8 LPM) and three different hot fluid rates (coil side, Qh= 1,1.5, and 2 LPM), four different injected air flow rates (Qa = 0.5,1,1.5, and 2 LPM), and invariant temperature difference () were tested at constant bubbles number (1400). To demonstrate the effect of bubble size, a sparger with orifice size of 0.1 mm, 0.8 mm and 1.5 mm were manufactured and used. The overall heat transfer coefficient (U), NTU, effectiveness and pressure loss were invested. The experimental results clearly showed that the heat exchanger's thermal efficiency was significantly improved with increasing the shell side flow rate, and the injected air flow rate, while it was only slightly improved with increasing the injected air bubble size. Although the latter finding is agreed with recent CFD published results, it needs more studies to be confirmed.

A Study on Heat Transfer Enhancement through Various Nanofluids in a Square Cavity with Localized Heating

Fri, 17 Sep 2021 00:00:00 +0800

A two-dimensional (2D) laminar flow of nanofluids confined within a square cavity having localized heat source at the bottom wall has been investigated. The governing Navier-Stokes and energy equations have been non dimensionalized using the appropriate non dimensional variables and then numerically solved using finite volume method. The flow was controlled by a range of Rayleigh numbers, length of heat source and nano particle volume fraction. The numerical results are represented in terms of isotherms, streamlines, velocity and temperature distribution as well as the local and average rate of heat transfer. A comparative study has been conducted for two different base fluids, ethylene glycol and water as well as for two different solids and. It is found that the ethylene glycol-based nanofluid is superior to the water-based nanofluid for heat transfer enhancement.

FCS-MPC strategy for PV grid-connected inverter based on MLD model

Xiao-juan Lu, Qing-BO Zhang — Sat, 18 Sep 2021 00:00:00 +0800

In the process of grid-connected photovoltaic power generation, the properties of photovoltaic grid-connected inverters directly determine the power quality output by the power generation system. In this work, in order to improve the power quality of the grid-connected inverter into the grid, we exhibit an approach toward establishing mixed logical dynamical (MLD) mode where logic variables were introduced to switch dynamics of the inverter. In addition, based on the model, our recent efforts in studying the finite control set model predictive control (FCS-MPC) and devising the output current full state observer are exciting for several advantages, including effectively avoiding the problem of the mixed integer quadratic programming (MIQP), lowering the THD value of the output current of the inverter circuit and improving the quality of the power that the inverter breaks into the grid. Finally, the effectiveness of mentioned methods is verified by MATLAB/Simulink simulation.

Multidisciplinary methodology for loss analysis of electromagnetic linear actuator considering load

Jiayu Lu, Qijing Qin, Cao Tan, Yingtao Lu, Bo Li, Xinyu Fan — Sat, 18 Sep 2021 00:00:00 +0800

As an energy converter，EMLAs have been widely used in industries. Multidisciplinary methodology is a preferred tool for the design and optimization of electromagnetic linear actuators (EMLA). In this paper, a multidisciplinary method was proposed for revealing the influence mechanism of load on EMLA’s loss. The motion trajectory of EMLA is planned through tracking differentiator, an adaptive robust control was adopted to compensate the influence of load on motion trajectory. A control-electromagnetic-mechanical coupling model was established and verified experimentally. The influence laws of load change on EMLA’s loss, loss composition and loss distribution were analyzed quantitatively. The results show that the data error of experiment and simulation result of input energy, mechanical work and iron loss are less than 3%. The iron loss accounts for less than 54.9% of the total loss under no load condition, while the iron loss increases with the increase of load. For iron loss distribution, only the percentage of inner yoke keeps increasing with the increase of load. The composition and distribution of loss is the basis of thermal analysis and design.

Aging Characteristics and Influencing Factors of the Sheds of Composite Insulators in Karst Regions of China

Wei Zhao, Miao Jiang, Jun Dong, Lee Li — Sat, 18 Sep 2021 00:00:00 +0800

In recent years, more and more high-voltage overhead transmission lines were built passing through the karst regions in southwestern China. This type of special landform seems to have an adverse effect on the aging of the sheds of the line suspension composite insulators, which may lead to unexpected flashover and line tripping. In order to find out the particularity of the aging characteristics of insulators operating in the karst regions, samples in operation were selected from both the karst regions and the flatlands. Hydrophobicity, amount of surface contamination, and contaminant composition of the sheds were studied, then a comparison of performance between the two was made, and the possible influencing factors that cause such differences were discussed. The results show that the overall aging of the sheds of the composite insulators operating at the karst regions is more aggravated, which is caused by the combined influence of factors including the special topography, climate, and pollution in the area. The strong wind crossing the col will bring about the mutual scraping on the edges and stress concentration at the root of the sheds, leaving scratches and root cracks; the infiltration from these rupture of acid liquid, if any, will accelerate the aging and corroding of the internal silicone rubber material; moreover, the carbonates enriched on the surface of the sheds will gradually transform into more corrosive sulfates in an acidic environment, leading to further deterioration and chalking of the sheds of the insulators.

A Investigation of Plans Shape and Glazing Percentage for the Energy Efficiency of Residential Buildings

Tayyebeh Yazarlou, Mohammad Djavad Saghafi — Sat, 18 Sep 2021 00:00:00 +0800

The plan shape of the room, the area of the window and the effect of the materials are the important parameters in determining the thermal needs of buildings. In traditional houses of hot and dry climate of Iran, the plan shape of the room, the ratio between the window area to the plan area and the effect of less materials have been studied. This study investigated the thermal performance of seven different models of the plans shape, five different ratios of window area to plan area and three material structures in a selected room of Yazd city using EnergyPlus software. Seven models have different plan shapes but the same area, whose thermal balance process calculations have been performed by CTF method. The results show that the best thermal comfort conditions for the residents are at the window area to floor area ratio of 12% for the brick buildings and 15% for the buildings with thermal insulation and proposed materials. The lowest cooling and heating needs are obtained in a room with east-west extension and a length-to-width ratio of about 1.38, which indicates the proper plan shape of the selected room. This research can be considered as a climatic strategy to improve the energy efficiency of residential buildings in Yazd.

Classification and Visualization of Stability of Surrounding Rock Based on Multi-dimensional Cloud Model

Wenlong Shen, Liming Xue, Zhixue Zheng — Sat, 18 Sep 2021 00:00:00 +0800

The stability classification of surrounding rock is a multiple index and uncertain system. The multi-dimensional cloud model is applied to the classification of surrounding rock stability. Multidimensional cloud model regards each index as an attribute. This model calculates the determinacy of each grade by multi-dimensional cloud generator, and determines the stability grade of surrounding rock according to the maximum, then applied in engineering examples, and compared with one-dimensional and two-dimensional cloud models and engineering practice to verify the accuracy of the model. Multidimensional cloud model is not very visualized. Multidimensional cloud model is reduced to one-dimensional cloud model and two-dimensional cloud model, and the level of multidimensional cloud model is visualized. Multidimensional cloud model is more comprehensive, the results are more accurate, and the visualization results are more intuitive. It provides an accurate and intuitive method for surrounding rock stability classification.

Coal Seam Permeability Improvement and CBM Production Enhancement by Enlarged Borehole：Mechanism and Application

Peng Chu, Zhuang Lu; Yuanyuan Liu, Zibin Zhu; Jin Gao, Xiaoxue Liao; Tao Yang — Sat, 18 Sep 2021 00:00:00 +0800

The permeability is a key factor to determine the efficiency of coalbed methane (CBM) production. The borehole enlargement technology using hydraulic and mechanical measures to cut coal is an effective method to increase the coal seam permeability and improve the efficiency of gas drainage. Reasonable design of the layout of boreholes is the prerequisite for efficient and economical gas drainage. In this paper, based on the strain-softening model, the stress and permeability model of the coal seam around the enlarged borehole was built, and based on the dual-medium model, the gas migration model in the coal seam was established. Then the borehole enlargement gas drainage engineering of E_9/10 coal seam in Pingdingshan No.8 coal mine was simulated by using COMSOL Multiphysics software. The distribution of stress and permeability in the coal seam around a borehole was analyzed, and the reasonable borehole radius of 0.25 m and reasonable borehole spacing of 6 m were determined. Finally, in Pingdingshan No.8 coal mine, field application was carried out in E_9/10 coal seam-21070 working face from the high-level gas drainage roadway. The results show that the actual average coal slag discharge rate is 77.82%, which achieved borehole enlargement. The natural gas flow rate from an enlarged borehole is 2.3-7.3 times that of a normal borehole, and the influence range of enlarged boreholes is more than 6m. The average gas drainage concentration of a group of enlarged boreholes is about 42%, and the average gas drainage amount is about 0.53 m³/min. After two months of gas extraction, the outburst risk in this area was eliminated, which provides a guarantee for safe coal mining.

A Novel Starting Impulse Suppression Method For Active Power Filter Based on Slowly Rising Curve

Jianfeng YANG, Yu DING — Sat, 18 Sep 2021 00:00:00 +0800

With the wide application of power electronic equipment in the power grid, the harmonic problem of the power grid is becoming more and more serious, which reduces the efficiency of power production, transmission, and utilization, and seriously interferes with the normal operation of the power grid. Based on the requirements of harmonic suppression and power system protection, a shunt active power filter (SAPF) is proposed as an effective harmonic suppression method. However, there are problems with impulse current and impulse voltage in the starting process of shunt active power filter. Impulse current and impulse voltage make the power grid and switchgear bear greater current stress and voltage stress, which seriously affect the security and reliability of the power grid, and may damage the switchgear. To effectively solve the problem of impulse current and impulse voltage at the starting time of SAPF, the starting process of SAPF is divided into uncontrolled rectification stage and transition stage. Firstly, the mathematical model of the DC side of APF is established. The causes of impulse current and impulse voltage in uncontrolled rectifier and transition phase are analyzed. By introducing voltage square, a new starting impulse suppression strategy of active power filter based on the slow rising curve is proposed, which fundamentally solves the problems of impulse current and impulse voltage. Simulation results verify the effectiveness and feasibility of the method.

A Hybrid Model Based on Back-Propagation Neural Network and Optimized Support Vector Machine with Particle Swarm Algorithm for Predicting Blade Icing on Wind Turbines

Xiyang Li, Bin Cheng, Hui Zhang, Xianghan Zhang, Zhi Yun — Sat, 18 Sep 2021 00:00:00 +0800

随着全球风能比例使用的不断增加，由风力涡轮机叶片结冰引起的发电效率降低和安全隐患引起了更多的研究关注。因此，准确预测风力涡轮机叶片上的结冰厚度很大，这可以作为充分的支持控制机器（SVM）和反向传播神经网络（BPNN）的优势，并添加了提出了一种基于动态限制规则的PSO-SVM和BPNN混合预测模型。以风轮机旋转工作状态下的三组结冰数据为例进行验证。通过与其他模型的比较分析，结果表明，该模型在预测风力涡轮机叶片的结冰方面具有更好的准确性和稳定性。

Comprehensive Study, Design and Economic Feasibility Analysis of Solar PV Powered Water Pumping System

Karthick K, Jaiganesh K, Kavaskar S — Sat, 18 Sep 2021 00:00:00 +0800

Solar photovoltaic (SPV) powered water pump is a very useful method to pump the water in agricultural sector. The energy efficient product can be operated with longer duration. They offer wonderful solutions compared to other conventional water pumping system as it needs less maintenance, simple in installation, zero fuel cost, longer operating life, highly reliable and free from production of greenhouse gases. In this paper we analysed the different topologies of DC-DC converter in terms of their operating region of MPPT, quality of input and output currents. We discussed about the MPPT algorithms to address partial shading effects in SPV array, present state of the technology, factors affecting the performance of the system, efficiency improvements and identified the research gaps. Also, the economic feasibility analysis has been done for the real time scenario using the Homer Pro software. The estimation of total dynamic head and horse power calculation has been done to decide the total load capacity. The economic analysis results such as cumulative cash flow over project lifetime of 25 years are presented. It is observed that the capital investment requirement is $7,425 for installing Fronius PV system that has a nominal capacity of 2.47 kW and annualized savings will be $134.93. In the long-term perspective, the return on investment is -2.18% as per the present tariff plan.

Evaluation of Energy Efficiency Performance of Heated Windows

Sat, 04 Dec 2021 00:00:00 +0800

The current study attempted to evaluate the performance of the heated windows by developing an experimental setup to test the window at various temperatures by varying the power input to the window. The heated double pane window was installed in an insulated box. A temperature gradient was developed across the window by cooling one side of the window using gel-based ice packs. The other face of the window was heated by passing power at different wattages through the window. The temperature of the inside and outside panes, current and voltage input, room and box temperature were recorded, and used to calculate the apparent R-value of the window when not being heated vs when being heated. It has been concluded from the study that the heated double pane window is more effective in reducing heat losses by as much as 50% than a non-heated double pane window, if the window temperature is maintained close to the room temperature. If the temperature of the window is much higher than the room temperature, the losses through the window appear to increase beyond that of a non-heated counterpart. The issues encountered during the current round of experiments are noted, and recommendations provided for future studies.

The Effect of a Liquid Cover on the Thermal Performance of a Salinity Gradient Solar Pond: An Experimental Study

Sat, 04 Dec 2021 00:00:00 +0800

Salinity Gradient Solar Ponds (SGSPs) offer the potential to capture and store solar energy for use in a range of domestic and industrial activities in regions with high solar insolation. However, the evaporation of water from these ponds is a significant problem that must be overcome for them to be deployed successfully. Thus, two ponds were constructed in the city of Nasiriya, Iraq. The two ponds were cylindrical with a diameter of 1.4 m and a total depth of 1.4 m. The water body in the two ponds was constructed with layer depths of 0.5, 0.75 and 0.1 m for the lower convective zone (LCZ), non-convective zone (NCZ) and the upper convective zone (UCZ) respectively. One of the two ponds was covered with a thin liquid paraffin layer (0.5 cm) to eliminate evaporation from the surface of the UCZ. The behavior of the standard SGSP and that of the covered pond with evaporation suppressed could be straightforwardly compared. The experimental units were run for six months from 1st of February to 31st of July 2019. It was shown in the first instance that by covering the pond with a thin layer of paraffin, that evaporation could be suppressed. The results showed that for the conventional SGSP, the temperature of the LCZ reached a maximum of ca. 76 °C while in the covered pond the temperature of the LCZ was consistently lower than that in the uncovered pond by approximately 5-6 °C. The results also indicated that the temperature of the UCZ in the covered pond was higher than that in the uncovered pond by about 10 °C in the second half of the study period. However, it was noted that on rainy days the paraffin layer was swept away from the surface; and this could hinder the implementation of thin liquid cover in the large SGSP.

Spark Plug Fault Recognition by Classification Method in A Spark Ignition Engine

Azrin Aziz — Sat, 04 Dec 2021 00:00:00 +0800

An intelligent practical approach was developed to recognize the spark plug fault in a SI engine by implementing classification method on the breakdown voltage signal of the spark plug. The time-domain data acquired from digital oscilloscope were converted to frequency-domain by employing Fast Fourier Transform (FFT) and a number of statistical features (standard deviation, mean, kurtosis and skewness) were extracted. significant features were then identified from the information gain (IG) scoring. KNN, ANN and SVM models were studied to identify the best classifier for classification stage. It was shown in the study that the KNN classifier acquired the highest classification accuracy of 100% on the test data compared to the other evaluated classifiers.

Inferential Statistics and Machine Learning Models for Short-term Wind Power Forecasting

Haichain Shao, Ming Zhang, Hongbo Li, Xing Deng — Sat, 04 Dec 2021 00:00:00 +0800

The qulity of the wind power system is susceptible to the inherent randomness, intermittentity and volatility of wind power generation, which always brings uncertainty to the optimal scheduling of the system. Therefore, accurate wind speed prediction can not only improve the quality of electricity, but also benefit the real-time power grid scheduling as well as wind farm grid-connected operation. In this paper, inferred statistics are used to infer general characteristics based on the selected dataset, which verifies thre there is indeed differences between two forecasting categories: Forecast Category 1 (0-11 hours ahead) and Forecast Category 2 (12-23 hours ahead). The corresponding quantative results are provided by the null hypothesis in z-tests. Five benchmark approaches such as persistence model, LMNN, NARX network, LMRNN and LSTM are used to verify the final performance of the forecasting result. The experiments based on the real dataset indicate that LSTM network has the highest forecasting accuracy compared with the ones that achieved by other benchmark approaches such as persistence model, LMNN, NARX network and LMRNN, and the 23-steps forecasting accuracy has improved by 19.61%.

Classification of Average Capillary Pressure Curves and Water Saturation Using J-Function and Flow Zone Indicator

Mohamed N Tarhuni, W R Sulaiman1, M Z Jaafar, K M Sabil — Sat, 04 Dec 2021 00:00:00 +0800

The X field is located in the southwestern part of block NX89 of Kentan Basin in Libya. This field is produced from Hailan multilayer consolidated sandstone with moderate rock property and a relatively low bubble point pressure (545 psia). Using the global hydraulic element technique, four rock types were identified for this reservoir ranging from medium to good reservoir quality. Six different layers were identified using stratigraphic modified Lorenz plot and available logs at which layer 4 and 6 had three sub-layers (a, b, and c). The reservoir was heterogeneous with a Lorenz coefficient value of approximately 0.72 and a Dykstra-Parsons value of 0.70. Capillary pressure was converted into reservoir conditions and was plotted with water saturation to result in 13 different Capillary pressure (P_c) curves. Using a multi regression method, both values lithology index and pore size distribution index were obtained for all samples. Leverett J-function was used to average the 13 capillary pressure curves into four main curves to represent the whole reservoir based on flow zone indicator values, ranging between 3 and 10. Capillary pressure was calculated and plotted with normalized water saturation; a single average curve was defined to represent the rest of the curves. Water saturation was calculated using single and multiple J functions and compared with the available logs. With multiple J functions, the matching results were good for both high and low-quality layers, whereas using a single J function, the match was poor, especially for low FZI layers such as H4c and H6a.

Fuzzy-TOPSIS Evaluation of Power Product-service system: a Framework Driven by Big Data

Xuchang Hu — Sat, 04 Dec 2021 00:00:00 +0800

Power product-service system (power PSS), which combines industrial electric products with electric energy services, is an effective solution for power enterprises under the background of the rapid development of power systems. In the life cycle of power PSS, evaluation decision of power PSS alternatives is of great significance for subsequent implementation. Driven by the big data of stakeholder comments, a power PSS evaluation framework is explored. Based on the multi-stakeholder comments of power PSS evaluation decision’s influence factors, the index system is constructed through analyzing and summarizing the co-occurrence matrix and semantic network diagram of high-frequency words. To determine the fuzzy index value of power PSS alternative, the stakeholders’ vague opinions expressed by trapezoidal fuzzy number are integrated by group decision method. Fuzzy concept is introduced into the classical Technique for Order Preference by Similarity to an Ideal Solution (TOPSIS) method and fuzzy-TOPSIS method is put forward by using the fuzzy index value. The improved TOPSIS is adopted to sequence the power PSS alternatives. The case of power PSS evaluation of six alternatives for a power enterprise shows that the explored framework is effective.

Discount Rate of China’s New Energy Power Industry

Yafei Rong, Xudong Sun — Sat, 04 Dec 2021 00:00:00 +0800

In the context of great reform in China’s electrical power industry, China’s new energy power industry has become the focus point. In this paper, we study the discount rate, which is a vital parameter for government and investors to invest and regulate in China’s new energy power market. The Capital Asset Pricing Model (CAPM) and Weighted Average Cost of Capital (WACC) are appropriate tools for discount rate computation. Our work proposes a method to limit problems arising from the CAPM assumptions. The main works are that applying Moving Average (MA) modifies the noise information of historical data and forecasts the discount rate values based on the CAPM and WACC methods. Specifically, we use simple MA method to modify the parameters of CAPM and WACC, to get correct discount rate from actual return results. By the way, the noise information of historical data mostly rejects the efficient estimates, so it is vital to remove the noise information. And then we propose a method to forecast the discount rate at the industry level by combined double MA, CAPM and WACC. Moreover, to validate the model results, we calculate and forecast the discount rates of hydropower, nuclear power, wind power and photovoltaic power industries in China. The results show that the discount rates of hydropower industry and nuclear power industry present relative stable trend, and the discount rates of wind power industry and photovoltaic power industry present small fluctuations in China from 2014 to 2019. In 2020, 2025, 2030, the photovoltaic power and wind power industries present increasing trend, the hydropower and nuclear power industries present decreasing trend. The focus of future development in China’s new energy power industries is still on the photovoltaic power and wind power industries.

Evaluation of green development level of electric energy in distribution network based on multilevel fuzzy comprehensive evaluation

Zhong fu Tan, Jing Wang, Cai xia Tan, Ge jirifu De — Sat, 04 Dec 2021 00:00:00 +0800

In order to further improve the comprehensive evaluation level of the development of green power network, this paper studies the green development level of electric energy of distribution network. Based on the existing literature at home and abroad, the index system for evaluating the green development of electric energy in distribution network is constructed from three dimensions: generation side, transmission and distribution side and sales side. Secondly, in order to avoid the influence of subjective factors, the model combining analytic hierarchy process (AHP) and entropy weight method is adopted to give index weight. Then, based on the fuzzy evaluation method, a multi-level fuzzy comprehensive evaluation model for the green development level of electric energy in the distribution network is constructed. Finally, five typical regions are selected for empirical analysis, and the results show that the model established in this paper can reflect the green development level of electric energy in the distribution network of each region and the areas to be improved in each region are proposed.

Using Grey Target Theory for Power Quality Evaluation Based on Power Quality Monitoring Data

Qiang Yu, Xiankai Chen, Xiaoyue Li, Chaoqun Zhou, Zhichao Li — Sat, 04 Dec 2021 00:00:00 +0800

Smart grid puts forward higher requirements for power quality. Power quality evaluation can provide decision-making basis for quality improving. Based on power quality monitoring data, a grey target method is proposed for power quality evaluation. The grey target is composed of power quality evaluation standard and power quality monitoring data to be evaluated. Combining with the characteristics of each power quality evaluation index, the target center of the whole grey target system is found. Then, the power quality monitoring data to be evaluated and the power quality standard mode are compared and analyzed to construct the power quality grey correlation difference information space. Finally, the target center coefficient and target degree of power quality are calculated to realize the comprehensive evaluation of power quality, and the evaluation grade of power quality monitoring data to be evaluated is obtained.

Research on the Intelligent Control Strategy of the Fuel Cell Phase-shifting Full-bridge Power Electronics DC-DC Converter

Lei Zhang, Yinlong Yuan, Yihe Sun, Yun Cheng, Dian Wu, Lei Ren — Sat, 04 Dec 2021 00:00:00 +0800

With the aggravation of energy problems, the development and utilization of new energy has become the focus of all countries. As an effective new energy, the fuel cell has attracted the attention of scholars. However, due to the particularity of proton exchange membrane fuel cell (PEMFC), the performance of traditional PI controlled phase-shifted full-bridge power electronics DC-DC converter cannot meet the needs of practical application. In order to further improve the dynamic performance of the converter, this paper first introduces several main topologies of the current mainstream front-end DC-DC converter, and analyzes their performance in the fuel cell system. Then, the operation process of the phase-shifted full-bridge power electronics DC-DC converter is introduced, and the shortcomings of the traditional PI control are analyzed. Finally, a double closed-loop adaptive fuzzy PI controller is proposed, which is characterized by dynamically adjusting PI parameters according to different working states to complete the intelligent control of phase-shifted full-bridge DC-DC converter. The simulation results in MATLAB/Simulink show that the proposed algorithm has good control effect. Compared with the traditional algorithm, the overshoot and stabilization time of the system are shorter. The algorithm can effectively suppress the fluctuation of the output current of the fuel cell converter, and is a very practical control method.

Initiation mechanism of transverse cracks in wind turbine blade trailing edge

Jinghua Wang, Leian Zhang, Xuemei Huang, Jinfeng Zhang, Chengwei Yuan — Sat, 04 Dec 2021 00:00:00 +0800

Transverse crack often occurs in the trailing edge region of the blade when subjected to the excessive fatigue load in edgewise. In this paper a refined model was established through local mesh refinement methods in order to investigate the initiation mechanism of crack and its extension in blade trailing edge. The material stress around the crack in trailing edge region under different thicknesses is calculated based on the fracture mechanics theory. Then the coupons test is conducted to verify the simulation results. The factors affecting the fatigue robustness of blade trailing edge are concluded by investigating the results of finite element analysis and coupons test. In final, a practical design scheme to prevent crack initiation is given for the manufacture of wind turbine blade.

Pressure-induced instability characteristics of a transient flow and energy distribution through a loosely bend square duct

Sat, 04 Dec 2021 00:00:00 +0800

An extensive numerical study on pressure-induced instability characteristics and energy distribution of a transient flow in a loosely bend square duct (BSD) is presented by applying a spectral-based numerical technique. The geometry is such that the bottom and the outer wall are heated while the other two in room temperature. The flow is accelerated due to the combined action of the non-dimensional parameters, the Grashof number Gr (= 1000), the curvature (= 0.001), and the Prandtl number Pr (= 7.0) over a large domain of the Dean number for . The structure of steady solutions (SS) has been investigated and obtained six branches of asymmetric SSs composed of 2- to 6-vortex solutions. Then, oscillating behavior, including transitional stages of unsteady flow (UF), is discussed by obtaining time-dependent solutions followed by power-spectrum analysis. Results show that the trend of UF endures in the sequence (steady-state, multi-periodic, steady-state, chaotic, multi-periodic, chaotic) as Dn is increased, and asymmetric 2- to 4-vortex solutions are evidently observed. Convective heat transfer (CHT) is then examined and presented through unsteady solutions (US), including energy contours, and it is observed that CHT is significantly enhanced by the secondary flow (SF). The present study reveals that the role of secondary vortices in transferring heat from the heated walls to the fluid is highly significant and heat transfer (HT) occurs substantially for the chaotic solution as well as chaotic flow regime. Finally, for the interest of validation, the present numerical result is also compared with the previously published experimental outcomes, and a good agreement is remarked.

Impact of Rotation on Fluid and Heat Flow in Bending Duct

Mohammad Zohurul Islam, Rabindra Nath Mondal, Suvash Chandra Saha — Mon, 24 Jan 2022 00:00:00 +0800

A depth understanding of the fluid past through a curved duct having rectangular cross-section with different aspect ratios are essential for various industrial and biomedical applications. The flow characterization in the rectangular duct has been studied by a large range of numerical and selective experimental studies. However, proper knowledge of the various rotational forces for different aspect ratios is important for better understanding of the transitional flow behaviour and the subsequent heat generation, which is required to improve further. The purpose of this study is to use various aspect ratios to get insight into the transitional flow pattern and heat generation in a rectangular domain. The Navier-Stokes equations are solved using the spectral method, while the Crank-Nicolson method is used to solve the heat equation. An in-house FORTRAN code is developed to get the numerical solution. For post-processing purposes, Tecplot-360 and Ghost-script tools are used. The present study analyses the development of Dean vortices that affect heat generation as well as thermal performance near the unstable solution region. From the vortex pattern of the Dean flows, transient characteristics of time-dependent results are calculated, where 2- to 8-vortex solutions are found for the periodic flow. For the chaotic flow regime, more complicated 4- to 13-vortex solutions are obtained. The chaotic flow that occurs at the certain range of Taylor number proficiently intensifies the heat transfer than the unperturbed, periodic or multi-periodic flow. The overall investigation reveals that in the rotating duct, the temperature-influenced buoyancy compulsion and centrifugal-coriolis joint forces are dominant, influencing the characteristic of the fluid and thus optimizing the transfer of heat.

Identification and Classification of Multiple Power Quality Disturbances Using a Parallel Algorithm and Decision Rules

Nagendra Kumar Swarnkar, Om Prakash Mahela, Baseem Khan, Mahendra Lalwani — Mon, 24 Jan 2022 00:00:00 +0800

Multiple power quality (MPQ) disturbance is a disturbance where two or more power quality (PQ) disturbances are superimposed on voltage signal. A compact and robust technique is required to identify and classify the MPQ disturbances. This manuscript investigated an algorithm which is designed using parallel processing of voltage with multiple power quality (MPQ) disturbance using Stockwell transform (ST) and Hilbert transform (HT). A MPQ identification index (IPI) is computed using statistical features extracted using the ST and HT from the voltage signal. IPI has different patterns for various types of MPQ disturbances which effectively identify the MPQ disturbances. A MPQ location index (IPL) is computed using the features extracted from the voltage signal using ST and HT. IPL effectively identify the initiation and end of PQ disturbances and thereby locating the MPQ events. Classification of MPQ disturbances is performed using decision rules in both the noise free and noisy environment with 20dB noise to signal ratio (SNR). Performance of the technique is better compared to ST and rule based decision tree (RBDT) technique in terms of accuracy of classification of MPQ disturbances. MATLAB software is used to perform the study.

Thermogravimetric and synergy analysis of the co-pyrolysis of coconut husk and laminated plastic packaging

Joselito Abierta Olalo — Mon, 24 Jan 2022 00:00:00 +0800

Unlike plastic, biomass can also be converted and produce high quality of alternative fuel. Co-pyrolysis of coconut husk (CH) and laminated plastic packaging (LPP) were done in this study. Synergy between this two feedstock was calculated by using thermogravimetric (TGA) and derivative thermogravimetry (DTG) analysis. Synergy evaluation using the various temperature and percentage composition of coconut husk with laminated plastic packaging as well as determining the activation energy by way of Coats-Redfern method. Results showed an activation energy ranging from 8 to 37 KJ/mol in the different percentage composition of the co-pyrolysis. Also, thermal degradation happens in two-stages in the co-pyrolysis of CH and LPP, in which CH degrades at temperature range of 210 to 390 ◦C while LPP degrades in temperatures 400 – 600 ◦C. Co-pyrolysis of CH and LPP can be an alternative fuel resource and can also reduce the waste problems in the community.

Research on Phase-shifted Full-bridge Circuit based on Frequency and Phase-shift Synthesis Modulation Strategy

Jiang Mingda, Che Yanbo, Li Hongfeng, Muhammad Ishaq, Xing Chao — Mon, 24 Jan 2022 00:00:00 +0800

The full-bridge converters usually use transformer leakage inductance and parallel resonant capacitors to achieve smooth current commutation and soft switching functions, which is easy to cause problems such as energy leakage and significant duty cycle loss. This paper designs a novel full-bridge zero-current (FB-ZCS) converter with series resonant capacitors and proposes a frequency and phase-shift synthesis modulation (FPSSM) control strategy based on this topology. Compared with the traditional parallel resonant capacitor circuit, the passive components used are significantly reduced, the structure is simple, and the energy loss is slight. By controlling the charging time of the capacitor, it can be achieved without additional switches or auxiliary circuits. The automatic control of capacitor energy based on input current addresses the low efficiency of the traditional control strategies. This paper introduces its principle in detail and verifies it through simulation. The module can be applied to a photovoltaic DC collection system using IPOS cascade to provide a new topology for large-scale, long-distance DC transmission.

Dynamic Simulation and Performance Analysis on Multi-energy Coupled CCHP System

Gejirifu De — Mon, 24 Jan 2022 00:00:00 +0800

Although the Combined Cooing, Heating and Power System (hereinafter referred to as “CCHP”) improves the capacity utilization rate and energy utilization efficiency, single use of CCHP system cannot realize dynamic matching between supply and demand loads due to the unbalance features of the user’s cooling and heating loads. On the basis of use convenience and wide applicability of clean air energy, this paper tries to put forward a coupled CCHP system with combustion gas turbine + ASHP ordered power by heat, analyze trends of such parameters as gas consumption and power consumption of heat pump in line with adjustment of heating load proportion of combustion gas turbine, and optimize the system ratio in the method of annual costs + energy environmental benefit assessment. According to hourly analogue simulation of cooling and heating loads in 100,000 km2 building and analysis on its matching features, it is found that energy and environmental protection benefits of ASHP are relatively poor although its annual costs are low; that shortage of cooling and heating loads in summer may be more than 6.35% due to ordering power by heat; that in combination with the evaluation method of primary energy consumption and zero CO2 emissions, the coupled CCHP + ASHP (load ratio of combustion gas turbine: 41%) system is the optimum configuration, and that this system structure and optimization method can provide some reference to the development of the coupled CCHP system.

Research on Power Consumption Anomaly Detection Based on Fuzzy Clustering and Trend Judgment

Wei Xiong, Xianshan Li, Yu Zou, Shiwei Su, Li Zhi — Mon, 24 Jan 2022 00:00:00 +0800

Among the end-users of the power grid, especially in the rural power grid, there are a large number of users and the situation is complex, and there are more cases of partial insulation damage and leakage or electricity theft by a small number of users. The operation and maintenance personnel need to spend a long time using manual inspection to determine the location of the abnormal watch box. In view of this situation, the method of subjective fuzzy clustering and quartile difference is adopted to determine the threshold, and the power consumption data of end users are divided into three regions: high, normal and low, which can be used to screen users in the area of abnormal power consumption. Then the trend judgment method is used to further accurately screen to improve the accuracy and reduce the number of users in the abnormal range. Finally, the abnormal electricity consumption users are determined according to the abnormal electricity consumption meter box. And the simulation environment is set to verify the application of membership fuzzy clustering and trend judgment in power consumption data partition.

Model-Free Sliding Mode Control for PMSM Drive System Based on UltraLocal Model

Kaihui Zhao,, Wenchang Liu, Tonghuan Yin, Gang Huang — Mon, 24 Jan 2022 00:00:00 +0800

This paper presents a novel model-free sliding mode control (MFSMC) method to improve the speed response of permanent magnet synchronous machine (PMSM) drive system. The ultra-local model (ULM) is first derived based on the input and the output of the PMSM. Then, the novel MFSMC method is presented, and the controller is designed based on ULM and MFSMC. A sliding mode observer (SMO) is constructed to estimate the unknown part of the ULM. Compared with the sliding mode control (SMC) method, the results of simulation and experiment demonstrate that the presented MFSMC method improves the dynamic response and robustness of the PMSM drive system.

A Value-at-Risk Based Approach for PMU Placement in Distribution Systems

chloe weiss — Mon, 24 Jan 2022 00:00:00 +0800

With the application of phasor measurement units (PMU) in the distribution system, it is expected that the performance of the distribution system state estimation can be improved obviously with the PMU measurements into consideration. How to appropriately place the PMUs in the distribution is therefore become an important issue due to the economical consideration. According to the concept of efficient frontier, a value-at-risk based approach is proposed to make optimal placement of PMU taking account of the uncertainty of measure errors, statistical characteristics of the pseudo measurements, reliability of the measurement instrument. The reasonability and feasibility of the proposed model is illustrated with a 12-node system. Simulation results indicated that uncertainties of measurement error and instrument fault result in more PMU to be installed, and measurement uncertainty is the main affect factors unless the fault rate of PMU is quite high.

Comprehensive Energy-Saving Optimization Model of Asynchronous Motor for Voltage Regulation Based on Static Synchronous Compensator

Shuqiao Dan — Fri, 01 Apr 2022 00:00:00 +0800

There are several problems existing in the direct starting of asynchronous motor such as large starting current, reactive power absorption from network side and weak interference-resistance etc. Aiming at this, a comprehensive energy-saving optimization model of asynchronous motor for voltage regulation based on static synchronous compensator (STATCOM) is put forward. By analyzing the working principle and operation performance of static synchronous compensator regulating voltage, a new energy-efficient optimization method for asynchronous motor is proposed based on the voltage regulator model to achieve soft start, continuous dynamic reactive power compensation and the terminal voltage stability control. The effectiveness and superiority of the proposed model is verified by the simulation analysis and the results of compare with the motor started directly.

Equipment Locating and Sizing Method for Distribution Energy Internetwork Based on Whole Life Cycle Cost

Qiang Li — Fri, 01 Apr 2022 00:00:00 +0800

As the development direction of smart grid, the locating and sizing method of distribution energy internetwork has become an important subject. Aiming at locating and sizing method of equipment in distribution energy internetwork including power network, thermal network and gas network, an optimizing model was proposed considering whole life cycle cost. Taking distribution network of system as the framework and the grid-connected position and allocation capacity of the key equipment as control variables, taking into account the purchase cost, installation cost, maintenance cost, comprehensive operation cost and residual value recovery of equipment, whiling taking the minimum comprehensive planning and operation cost of the system as the objective function, at the same time taking into account power balance constraints considering various forms of energy, system operation reliability constraints and other constraints. distribution energy internetwork based on IEEE33 bus distribution system was used to locate and capacitate equipment. The proposed model was verified and solved by chaotic particle swarm optimization. The simulation example shows that the method proposed in this paper is suitable for locating and sizing of equipment in distribution energy internetwork, and can improve the social and economic benefits of system operation.

Optimization scheme of integrated community energy utilization system based on improved sine-cosine algorithm

zhang xin, jinpeng jiang, haoran zheng, jihong zhang — Fri, 01 Apr 2022 00:00:00 +0800

With the rapid development of the multi-energy technology of cold, heat, electricity, and gas, the construction of an integrated energy utilization system at the urban community level has become possible. China has a high consumption of natural gas in winter, but taking natural gas as a fuel input for cold-heat-electricity supply units may cause problems. The integrated community energy utilization system cannot stabilize the output of electricity and heat due to natural gas shortages. Besides, the operation economy of this system still needs to be improved. In view of the above problems, an energy supply structure with garbage power as the core of the integrated community energy utilization system was established firstly in the study. Secondly, an optimal dispatching model of the integrated community energy utilization system was established by making use of the regulating characteristic of the community load. Thirdly, the sine-cosine algorithm based on nonlinear factors and segmented weight was presented to solve the optimal dispatching model of the integrated community energy utilization system. The results showed that the daily system operating cost was effectively reduced by the algorithm proposed in the study, and the electrical load regulation and the economically optimized operation of the integrated community energy utilization system was realized.

Optimal Decision-Making of Trans-Provincial Electricity Market Subjects with Risks under Renewable Portfolio Standards

Shu Yi Chen, Hui Wang, Chao Zi Wu, Cheng Hao Xu — Fri, 01 Apr 2022 00:00:00 +0800

Abstract: The randomness and uncertainty of renewable energy generation are expected to significantly change the optimal decision-making of trans-provincial electricity market subjects. Therefore, it is beneficial to optimize the interests of each of these subjects, considering the unpredictable risks of renewable energy under the renewable portfolio standards (RPS) and researching their effects on the optimal decision-making of trans-provincial electricity market multi-subjects. First, we develop a trans-provincial trading market mechanism for renewable energy and clarify the electricity supply and demand relation and the green certificates supply and demand relation of trans-provincial electricity market multi-subjects. Then, under the RPS, we construct a multi-subject game model of the power supply chain that recognizes the risks, and adopt the reverse induction method to discuss the optimum risk-taking judgment of each subject in the trans-provincial electricity market. Finally, we use MATLAB to verify the viability and efficacy of the proposed game model, and obtain a certain reference value for the optimal decision-making of trans-provincial electricity market subjects. In summary, we consider the uncertainty risk of renewable energy under RPS, study the effects of the green certificate price and risk aversion coefficient in the RPS mechanism on the optimal decision-making of trans-provincial electricity market subjects, and obtain the changing trends of the green certificate price and risk aversion coefficient of two different power products and those of different electricity market subjects under their influence, which have certain reference value for studying the factors affecting the optimal decision-making of trans-provincial electricity market subjects.

Stepwise Pyrolysis by LBCR Downstream to Enhance of Gasoline Fraction of Liquid Fuel from MMSW

Nugroho Agung Pambudi — Fri, 01 Apr 2022 00:00:00 +0800

Pyrolysis is one of thermal cracking method to convert the hydrocarbon material into liquid fuel. The quantity and quality of mass yield of liquid fuel on the pyrolysis process are depend on several operation condition including temperature, reaction time, kind of catalyst and type of the reactor. A gasoline fraction was maximum product be expected in which it was the best one considered. Therefore, this study has attempt to increase the gasoline fraction in the liquid fuel with stepwise pyrolysis with a long bed catalytic reactor (LBCR) downstream. The LBCR downstream that equipped with the top and bottom outlet were employed. The source to produce the gasoline in this study was mixed municipal solid waste (MMSW). The activated natural dolomite at 500 °C was used on LBCR downstream to allow the repetition of the secondary cracking. Also, the temperature of LBCR reactor was setup varied from 200-300 °C and the pyrolizer was held 400 °C. To analyze the gasoline fraction and physical properties of liquid fuel, Gas Chromatography-Mass Spectroscopy (GC-MS) method and ASTM standard were employed. The experimental results revealed that there was a significant increase in the gasoline fraction of liquid fuels compared using of direct catalytic cracking and absence of catalysts. By use a LBCR at 250 °C, the liquid fuel obtained of top outlet (TO) and bottom outlet (BO) have 84.08 and 56.94 percent peak area of gasoline fraction (C5-C12), respectively. The average value (TO and BO) of gasoline fraction at 250 °C by LBCR was 70.51 percent peak area and it was increased around 93.6% and 51.14% compared without catalyst and direct catalytic, respectively. Further, pyrolytic liquid oils were found to have kinematic viscosity 2.979 and 0.789 cSt, density 0.781 and 0.782 gr/cm3, and flash point < -5 °C for BO-250 and TO-250 liquid fuel, respectively. These results show that BO liquid fuel was comparable to diesel conventional fuel while TO liquid fuel was comparable to gasoline conventional fuel. Evidently, the presence of LBCR was made a major contribution to generate multi secondary cracking and to produce more gasoline fraction from mixed MMSW feedstock and to increase the physical properties of liquid fuel.

An Insight into the Second-Harmonic Current Reduction Control Strategies in Two-Stage Converters

Lei Ren, Lei Zhang — Fri, 01 Apr 2022 00:00:00 +0800

Due to the components at twice the fundamental frequency of output voltage in the instantaneous output power of a two-stage single-phase inverter (TSI), the second harmonic current (SHC) is generated in the front-end dc-dc converter (FDC). To reduce the SHC, optimizing the control strategy of the FDC is an effective and costless approach. From the view of visual impedance, this paper conducts an intensive study on the SHC reduction strategies. Origin of the SHC is illustrated first. Then, the equivalent circuit models of the FDC under different control strategies are proposed to analyze the SHC propagation characteristic. The derived model can offer a better insight into how the inductor SHC is affected by control parameters. According to the derived models, a synthesis of different control strategies is presented and the relevant control parameters are listed for improving suppression effect. The benefits and limitations of these control strategies are also discussed. Based on the proposed equivalent circuit models, optimization methods are proposed to achieve a better effect. A 1500VA TSI prototype is built and simulated on MATLAB, verifying the effectiveness of the proposed optimization methods. This paper is aimed to provide a guideline for the control design and control optimization of the TSIs.

A STA current-constrained control for PMSM speed regulation system with function disturbance observer

Bin Zhang, Boqiang Wei — Fri, 01 Apr 2022 00:00:00 +0800

The non-cascade permanent magnet synchronous motor control system has the advantages of simple structure and less adjustable parameters, but the non cascade structure needs to solve the problem of over-current protection.In this paper, a current constrained control method is used to limit the starting current to a safe range,At the same time, in order to ensure the robustness and rapidity of the system,Super twist current constraint controller (CCSTA) is generated by combining super twist algorithm (STA) with current constraint control;Considering the diversity of internal and external disturbances, a functional disturbance observer (FDOB) is proposed to compensate the matched and unmatched disturbances, which further improves the robustness of the system.

A New Diagnostic Method Applied to Gearbox Missing Gear Faults ——LOD-ICA

Lida Liao, Bo Xiao, Kan Huang, Bin Huang, Kang Zhang — Fri, 01 Apr 2022 00:00:00 +0800

The LOD method based on noise-assisted analysis is a new adaptive time-frequency analysis method based on the improvement of the LOD method. The improved LOD method alleviates the signal modal mixing problem generated by the LOD method when decomposing mixed signals to a certain extent, but the method, like EMD, LMD method and LOD method, still cannot completely solve the signal modal mixing problem. The fast ICA method, however, is a widely used method for blind source separation of mixed signals in the field of human voice analysis, but requires a high number of data channels. Based on this, this paper proposes a new method LOD-ICA method that combines the fast ICA method and the LOD method based on noise-assisted analysis. The LOD method with added white noise can provide enough virtual channel data for the fast ICA method; with enough observation channels, the fast ICA algorithm can solve the modal mixing problem of the LOD method with added white noise to achieve blind source separation of the signal. The superiority of the LOD-ICA method in solving the modal mixing problem when processing vibration signals is verified by the comparative analysis of the LOD-ICA method and the LOD method based on noise-assisted analysis in simulated signals. The LOD-ICA method is applied to the wind turbine gearbox fault feature extraction, and the fault sign of the vibration signal is successfully extracted, which verifies the effectiveness of the LOD-ICA method in processing the vibration signal of rotating machinery.

Characteristics of diesel/n-butanol blend on a common rail diesel engine with exhaust gas recirculation

Yanfei Chen, Jingjing He, Hao Chen, Xin Su, Bin Xie — Fri, 01 Apr 2022 00:00:00 +0800

20% n-butanol is blended in diesel by volume (noted as D80B20) and experiment has been carried out to study the effect on the combustion and emission characteristics based on a common rail diesel engine with exhaust gas recirculation (EGR) system. Results reveals that D80B20 has longer ignition delay, shorter combustion duration and higher maximum in-cylinder temperature than pure diesel (noted as D100). Further, the number concentration and volume concentrations of ultrafine particles decrease significantly while NOx emissions increase a little with the addition of n-butanol. When the exhaust gas is induced into cylinder, NOx emissions significantly decrease and ultrafine particles emissions increase. The number geometric mean diameters and volume geometric mean diameters of ultrafine particles increase with EGR ratio. Compared to D100 without EGR, D80B20 with 20% EGR ratio can reduce both NOx and ultrafine particles emissions at 0.14MPa BMEP and 0.56MPa BMEP.

Development of Vehicle-to-Grid System to Regulate the System Parameters of Microgrid

Om Prakash Mahela, Baseem Khan, Rupendra Kumar Pachauri — Mon, 23 May 2022 00:00:00 +0800

A vehicle-to-grid (V2G) power is a new concept for the design of electric vehicles. An electric vehicle having capability of V2G effectively controls and provides charge/discharge. This enables charging when the electricity is cheap and enables discharging when the electricity is costly. This paper proposes a design of vehicle-to-grid system interfaced with the microgrid and utilized for regulating frequency on a microgrid during a period of 24 hours cycle. A microgrid is designed and divided into four components. First component is a diesel generator which is used to act as the base power generator. Second component consists of renewable energy (RE) power plants which include solar photovoltaic (PV) and wind plants. Third component is a V2G system. Last component is the load connected to the microgrid. Microgrid is designed with suitable size to represent a community of which consists of one thousand households for the day period of low consumption in spring or fall seasons. Total 100 EVs are modeled as base model to realize a 1:10 ratio for cars to households which indicates a possible scenario in a near future. System parameters such as frequency and voltage are maintained with the permissible limits. Detailed analysis of the active power, reactive power, voltage, and current is carried out to establish the effectiveness of the proposed design of the system. Proposed study is effectively realized in the MATLAB/Simulink environment.

Case analysis of a Pump-driven Heat Pipe Heat Recovery Ventilator in an Existing Experiment Building

Zhun Li, Zhengrong Ouyang, Tianbao Sun, Qiang Li, Xiaobo Zhao, Rong Yu — Mon, 23 May 2022 00:00:00 +0800

The building energy consumption is an important part among the total society energy consumption, in which the energy consumption for air conditioning occupies almost 70%. The energy consumption of the air conditioning system for fresh air handling can be saved effectively when the exhaust air energy could be recovered to preheat or precool the fresh air. Considering the install locations requirements on field, the pump-driven heat pipes (PHP) were developed as heat recovery ventilators (HRVs) and used in an existing experiment building in Beijing Urban. The thermal performance of the PHP HRVs were tested in real operation time periods under winter running mode. Both the power and heat consumption of the modular air handling units with and without HRVs were monitored and obtained, as well as the hourly power and heat consumption. The energy savings of HRVs were analyzed. The results indicate that the PHP HRVs can work steadily and meet the energy recovery need well. The temperature effectiveness of the HRVs can be kept from 60% to 70%. The test total energy saving rate was 24.48%, and the average hourly heat consumption reduced by 28.54%. The daily energy consumption can be saved by 118 kWh, and the energy savings can reach to 9440 kWh for a whole winter.

Solar Powered Vaccine-19 Cold Storage for a Remote Clinic: Prospect and Challenge

Indra Mamad Gandidi, Apri Wiyono, Nugroho Agung Pambudi, Rahmat Romadhon — Mon, 23 May 2022 00:00:00 +0800

The rapid spread of the COVID-19 pandemic has forced countries globally to stock vaccines in cold storage to protect them from damage and maintain stability. However, remote clinics are faced with vaccine storage challenges due to a lack of electricity supply. Therefore, this study examines and discusses the prospects and challenges of applying solar-powered cold storage to provide cold rooms for remote clinics. The result is expected to contribute to cold chain vaccine management technology significantly.

Short-Term Prediction of PV Power Based on Feature Transfer

Zhongyao Du, Xiaoying Chen, Hao Wang, Xuheng Wang, Yu Deng, Liying Sun — Mon, 23 May 2022 00:00:00 +0800

The open sharing of power data and the grid connection of high-permeability renewable energy are the inevitable choice to achieve the goal of "carbon peaking and carbon neutralization". In this article, based on the open and shared power data, a short-term PV power prediction model based on feature transfer learning is established to improve the generalization ability of the prediction model and solve the problem of insufficient training data of the prediction system of new grid connected PV power stations. Integrate the structure model, heat dissipation conditions and losses coefficient of PV modules. Clear-Sky entropy, characteristic of seasonal and weather data feature based on uniform manifold approximation and projection for dimension reduction (UMAP) jointly describe the main meteorological characteristics of the location of PV power station. Taking gate recurrent unit (GRU) neural network as the framework, the open and shared PV power data as the source domain training label, and a small amount of power data of the new grid connected PV power station as the target domain training label, the neural network hidden layer is shared between the target domain and the source domain. The full connection layer is established in the target domain, and the regularization constraint is introduced into fine-tune to suppress the over fitting in feature transfer. The power prediction is completed according to the actual power data of PV power stations. The results show that the short-term PV power prediction based on feature transfer has strong generalization ability.

Study of Denoising in the Electricity Anti-Stealing Detection Based on VMD-WTD Combination

Mon, 23 May 2022 00:00:00 +0800

In order to solve the failure of electricity anti-stealing detection device triggered by the noise mixed in high-frequency electricity stealing signals, a denoising method based on variational mode decomposition (VMD) and wavelet threshold denoising (WTD) was proposed in this paper to extract the effective high-frequency electricity stealing signals. First, the signal polluted by noise was pre-decomposed using the VMD algorithm, the instantaneous frequency mean of each pre-decomposed components was analyzed, so as to determine the optimal K value. The optimal K value was used to decompose the polluted signal into K intrinsic mode components, and the sensitive mode components were determined through the cross-correlation function. Next, each sensitive mode was reconstructed. Finally, the reconstructed signal denoised using the wavelet threshold to obtain the denoised signal. The simulation analysis and experimental results show that the proposed method is superior to the traditional VMD method, as it can effectively eliminate the noise and enhance the reliability of high-frequency electricity stealing signal detection.

Research on Typical Application Scenarios and Economic Benefit Evaluation Methods of Energy Storage System

Pinduan Hu, Ting Pan, Ming Zeng, Shi Tian, Zhukui Tan, Yikai Sun — Mon, 23 May 2022 00:00:00 +0800

Energy storage system is an important means to improve the flexibility and safety of traditional power system, but it has the problems of high cost and unclear value recovery path. In this paper, the typical application scenarios of energy storage system are summarized and analyzed from the perspectives of user side, power grid side and power generation side. Based on the typical application scenarios, the economic benefit assessment framework of energy storage system including value, time and efficiency indicators is proposed. Typical energy storage projects are selected for economic benefit calculation according to different scenarios, and key factors are selected for sensitivity analysis. Finally, the key factors affecting economic benefit of the energy storage system are analyzed.

Experimental Investigation on Prototype Latent Heat Thermal Battery Charging and Discharging Function Integrated with Solar Collector

Mon, 23 May 2022 00:00:00 +0800

This paper reports the performance investigation of a newly developed Latent Heat Thermal Battery (LHTB) integrated with a solar collector as the main source of heat. The LHTB is a new solution in the field of thermal storage and developed based on the battery concept in terms of recharge ability, portability and usability as a standalone device. It is fabricated based on the thermal battery storage concept and consists of a plate-fin and tube heat exchanger located inside the battery casing and paraffin wax which is used as a latent heat storage material. Solar thermal energy is absorbed by solar collector and transferred to the LHTB using water as Heat Transfer Fluid (HTF). Charging experiments have been conducted with a HTF at three different temperatures of 68, 88, and 108 °C and three different flow rates of 30, 60 and 120 l/h. It is followed by discharging experiments on fully charged LHTB at three different temperatures of 68, 88, and 108 °C using HTF at three different flow rates of 30, 60 and 120 l/h. It is found that both higher HTF inlet temperature and flow rate have a positive impact on stored thermal energy, however, charging efficiency was decreased by increasing the HTF flow rate. The highest charging efficiency of 29% was achieved using HTF of 108 °C at a flow rate of 30 l/h. Most of paraffin melted in this case, while part of the paraffin remained solid in other experiments. On the other hand, the results from discharging experiments revealed that both recovered thermal energy and recovery efficiency increased by either increasing the LHTB temperature or HTF flow rate. Highest recovered thermal energy of 5,825 KJ at 35% recovery efficiency achieved at LHTB of 108 °C using 120 l/h of HTF.

An An Advanced Control Strategy for Dual-actuator Driving System in Full-scale Fatigue Test of Wind Turbine Blades

Guanhua Wang, Jinghua Wang; Xuemei Huang; Leian Zhang, Weisheng Liu — Mon, 23 May 2022 00:00:00 +0800

A new dual-actuator fatigue loading system of wind turbine blades was designed. Compared with the traditional pendulum loading mode, the masses in this system only moved linearly along the loading direction to increase the exciting force. However, the two actuators and the blade constituted a complicated non-liner energy transferring system, which led to the non-synchronization of actuators. On-site test results showed that virtual spindle synchronous strategy commonly used in synchronous control was undesirable and caused the instability of blade’s amplitude eventually. A cross-coupled control strategy based on active disturbance rejection algorithm was proposed. Firstly, a control system model was built according to the synchronization error and tracking error. Furthermore, based on arranging the transition process, estimating the system state and error feedback and compensating disturbance, an active disturbance rejection controller was designed by adopting the optimal control function. Finally, on-site test results showed that the cross-coupled control strategy based on the active disturbance rejection algorithm could ensure the synchronization of two actuators. The maximum speed synchronization error of the two motors was less than 16 RPM, the displacement synchronization error of the two actuators was less than 0.25mm and approaching zero after 4 seconds, and the peak value of vibration of the blade was less than 5mm, which satisfied the fatigue test requirement.

Soot Distribution and Thermal Regeneration of Marine Diesel Particulate Filter

Xiangli Wang, Peiyong Ni — Mon, 23 May 2022 00:00:00 +0800

Particles from marine diesel engine exhaust gas have caused serious air pollution and human health. Diesel particulate filter (DPF) can effectively reduce particle emissions from marine diesel engines. The distribution and regeneration of soot in DPF are two important issues. In this paper, a mathematical model of a marine DPF was built up and the particle trap process and the regeneration dynamics were simulated. The results show that the cake soot mass concentrations during trap process increase linearly with the increase of the exhaust gas flows while the depth soot mass concentrations firstly increase linearly and then keep constant. Soot is mainly concentrated in the front and rear portion of the filter and less soot is in the middle. The soot distribution in the cake and depth layer shows the unevenness during the trap and regeneration process. The initial soot loadings have great effects on pressure drops and soot mass concentrations before regeneration, but little effect after regeneration. The exhaust gas temperature heated to 850 K can achieve 94% efficiency for the DPF regeneration. There is no obvious difference in pressure drops and soot mass concentrations between fast heating and slow heating. The heating duration of exhaust gas has an important impact on DPF regeneration.

Modeling and Simulation Analysis of Solar Thermal Electric Plants Based on Petri Net

LU Xiao-juan — Mon, 23 May 2022 00:00:00 +0800

At present, solar thermal power generation is in the demonstration stage, and the large-scale production is affected by many factors. In view of the characteristics of different operating modes of photothermal power generation, it is analyzed that the turbine needs to be started and stopped frequently due to different operating modes, which will lead to the instability of the output energy and the reduction of power generation efficiency. In this paper, the dynamic equation of energy conversion process is established by using the law of conservation of energy and conservation of mass. Combined with the logic switching criterion of the system, the system model was established by using the extended differential Petri net, and the validity and accuracy of the model were verified. Through the Petri net model of the system, the system's working mode switching and power generation situation are analyzed due to the difference of direct normal irradiation intensity (DNI). Finally, the accuracy of the model is proved by comparing it with experimental data of the photovoltaic and thermal demonstration projects that have been connected to the grid.

Progress on Catalyst Layer Materials for Proton Exchange Membrane Fuel Cells

stefanos tzelepis, Kosmas Kavadias — Thu, 21 Jul 2022 00:00:00 +0800

The constant increase in energy demand and related environmental issues have made fuel cells an attractive technology as an alternative to conventional energy technologies. Like any technology, fuel cells face drawbacks that scientific society has been focused on to improve and optimize the overall technology. Thus, the cost is the main inhibitor for this technology due to the significantly high cost of the materials used in catalyst layers. The current discussion mainly focuses on the fundamental electrochemical half-cell reaction of hydrogen oxidation reaction (HOR) and oxygen reduction reaction (ORR) that are taking place in the catalyst layers consisting of Platinum Platinum-based and Platinum-non noble metals. For this purpose, studies from the literature will be presented, analyzing the main findings from each study by highlighting and comparing the variations on the catalytic activity within the experimental catalyst layers and the conventional. Furthermore, an economic analysis of the main platinum group metals (PGMs) such as Platinum, Palladium and Ruthenium will be introduced by presenting the economic trends for the last decade.

Numerical-Experimental Analysis of Minimization of Frost Formation in Flat Plates

Thu, 21 Jul 2022 00:00:00 +0800

The study presents a numerical-experimental analysis of the formation process of porous ice in flat plates with different surface treatments. This phenomenon occurs when the flow of the air and water vapor mixture comes in contact with surfaces that present temperatures below 0°C, found in several commercial and industrial applications that reach low temperatures, creating a porous structure, characterized by irregular ice crystals. Its accumulation implies an increase in energy demand and a decrease in the performance of various equipment involved in the refrigeration process, reducing its efficiency and making it necessary to periodically remove it, resulting in expenses for the defrost process. In this context, a low-cost experimental apparatus was developed, enabling an experimental analysis of the phenomenon under study. The environmental conditions evaluated are the temperature of the cold surface, room temperature, humidity, and air velocity. The material of the surfaces under study are aluminum, copper, and brass with different surface finishes, designated as smooth, grooved (hydrophilic), and varnished (hydrophobic). The numerical-experimental analysis demonstrates measurements and simulations of the thickness, surface temperature, and deposition speed of the porous ice layer as a function of the elapsed time. The numerical results were in good agreement with the experimental results, indicating that the varnished surface, with hydrophobic characteristics, presents greater difficulty in providing the phenomenon.

Anomaly detection and pattern differentiation in monitoring data from power transformers

jun zhao, Shuguo Gao, Yunpeng Liu, quan wang, Ziqiang Xu, Yuan Tian, Lu Sun — Thu, 21 Jul 2022 00:00:00 +0800

Aiming at the problem of abnormal data generated by a power transformer on-line monitoring system due to the influences of transformer operation state change, external environmental interference, communication interruption, and other factors, a method of anomaly recognition and differentiation for monitoring data was proposed. Firstly, the empirical wavelet transform (EWT) and the autoregressive integrated moving average (ARIMA) model were used for time series modelling of monitoring data to obtain the residual sequence reflecting the anomaly monitoring data value, and then the isolation forest algorithm was used to identify the abnormal information, and the monitoring sequence was segmented according to the recognition results. Secondly, the segmented sequence was symbolised by the improved multi-dimensional SAX vector representation method, and the assessment of the anomaly pattern was made by calculating the similarity score of the adjacent symbol vectors, and the monitoring sequence correlation was further used to verify the assessment. Finally, the case study result shows that the proposed method can reliably recognise abnormal data and accurately distinguish between invalid and valid anomaly patterns.

Production Dynamic Prediction Method of Waterflooding Reservoir Based on Deep Convolution Generative Adversarial Network (DC-GAN)

liyuan xin, Xiang Rao, Xiaoyin Peng, Yunfeng Xu, Jiating Chen — Thu, 21 Jul 2022 00:00:00 +0800

The rapid production dynamic prediction of water-flooding reservoirs based on well location deployment has been the basis of production optimization of water-flooding reservoirs. Considering that the construction of geological models with traditional numerical simulation software is complicating, the computational efficiency of the simulation calculation is often low, and the numerical simulation tools need to be repeated iteratively in the process of model optimization, machine learning methods have been used for fast reservoir simulation. However, traditional artificial neural network (ANN) has large degrees of freedom, slow convergence speed and complex network model. This paper aims to predict the production performance of water flooding reservoirs based on deep convolutional generative adversarial network (DC-GAN) model, and establish a dynamic mapping relationship between well deployment and output oil saturation. The network structure is based on an improved U-Net framework. Through deep convolutional network and deconvolution network, the features information of input well deployment images are extracted, and the stability of the adversarial model is strengthened. The training speed and accuracy of the proxy model are improved, and the oil saturation of water flooding reservoirs is dynamically predicted. The results show that the trained DC-GAN has good performances in predict oil saturation via input well employment figure. The cosine similarity between the oil saturation map given by the trained DC-GAN and the oil saturation map generated by the numerical simulator is compared. In all, DC-GAN is an effective way to conduct a proxy model to quickly predict the production performance of water flooding reservoirs.

Comparative experimental analysis on oxidation and spontaneous combustion

haitao wang — Thu, 21 Jul 2022 00:00:00 +0800

In order to study the similarities and differences laws of thermal oxidation characteristics in multi-coal seam mines, and better predict coal spontaneous combustion in each coal seam of a coal mine, this paper takes five coal seams in Xin'an Coal Mine of Shuangyashan as the research object. The coal quality characteristics of No.6, No.8, No.9, No.12 and No.20 coal seams are analyzed by automatic industrial analyzer. The self-made temperature programming system is used to analyze the thermal oxidation process of coal seams with five different particle sizes (0–0.9mm, 0.9–3mm, 3–5mm, 5–7mm, 7–10mm).The experimental results show that the concentration of CO produced by thermal oxidation in five coal seams increases exponentially with temperature. It can be used as an important indicator of coal spontaneous combustion prediction. The CO production rate is related to the particle size of coal, that is, the smaller the particle size, the faster the production rate, and the higher the temperature, the more the production, the amount of CO released from No.8 and No.12 coal seam is more than that from No.6, No.9 and No.20 coal seam, which indicates that anthracite and weak cohesive coal in coal seam have great influence on CO release during coal thermal oxidation.

Numerical study and economy analysis of two heated crude oil pipelines laid in one ditch

Wenpeng Guo — Thu, 21 Jul 2022 00:00:00 +0800

In this paper, the transportation economy of two heated crude oil pipelines laid in one ditch is analyzed by taking into account the influence of operating temperature, interval between two pipelines, and distance between two heating stations on the consumption of heating energy. To analyze the transportation economy, the two heated crude oil pipelines laid in one ditch are simulated under four operating conditions based on an unstructured finite volume method. Compared with laying two crude oil pipelines separately in two ditches, the results attest notably higher soil temperature, meaning reduced heat dissipation of each pipeline by laying two pipelines in one ditch. It is inferred that for the same desired oil temperature at the inlet of heating station, laying two pipelines in one ditch requires lower oil temperature at the outlet of heating station, indicating decreased energy cost at the heating station and improved transportation economy. Then economy analysis of four configurations of laying two pipelines in one ditch is performed. By comparing the results of four conditions, the interval between two pipelines of 1.2m is found to save the energy most efficiently, which is as large as 26.6% compared with that of laying two pipelines in two separate ditches. In addition, narrowing the pipeline interval and extending the distance between heating stations is beneficial to save heating energy. This study is expected to provide valuable guidance for operation optimization of heated crude oil pipelines.

A Design of 220kV line protection action deduction system based on numerical simulation

Daming Zhou — Thu, 21 Jul 2022 00:00:00 +0800

Accurate conditions monitoring and early wrong action warnings of relay protection in the Smart Substation is the basic guarantee to realize the normal operation of primary and secondary system of the power grid. At present, the traditional operation and maintenance monitoring methods of relay protections have poor timeliness, while some automatic monitoring methods have low intuition and insufficient early warning performance, which is not conducive to the analysis of fault causes. In this paper, a relay protection conditions monitoring and action deduction system based on numerical simulation technology is designed. The protection operation logic includes distance protection logic, longitudinal differential protection logic, zero sequence over-current protection logic, trip to reclosing logic, and equipment software and hardware conditions are twinned to realize the tracking of relay protection operation conditions and wrong action warnings, which effectively improves the operation and maintenance efficiency of the secondary system in the intelligent substation.

Estimating Energy Consumption and by the Multiple Regression Models.

Baraka achraf CHAKIR — Thu, 21 Jul 2022 00:00:00 +0800

The building sector is one of the main energy-consuming sectors in Morocco. In fact,
it accounts for 33% of final consumption of energy and records a high increase in the annual
consumption of energy caused by the planned large-scale projects. Indeed, energy consumption
of the building sector is experiencing a significant acceleration justified by the rapid
development of the housing stock, estimated at an average increase of 1.5% per year.
of the housing stock, which is estimated at an increase of about 6.4%.
In this sense, the building constitutes an important potential source in terms of rationalization of
energy consumption and energy savings through the adoption of energy efficiency measures.
Energy consumption control efforts in the residential building sector involve socio-economic,
technological, and environmental concerns that require sophisticated research. Indeed, different
types of quantitative models have been developed and examined in order to find a solution for
the optimization of energy consumption.
In this article, we present a overview of the principal thermal building models energy efficiency
of buildings, also we suggest an example of black box modeling simulation in order to study the
performance of a solar system of a reference building in Casablanca.

Low Carbon Building Design Optimization Based on Intelligent Energy Management System

Zhenyi Feng, Nina Mo, Shujuan Dai, Yu Xiao, Xia Cheng — Fri, 28 Oct 2022 00:00:00 +0800

The construction of relevant standards for building carbon emission assessment in China has just started, and the quantitative analysis method and evaluation system are still imperfect, which hinders the development of low-carbon building design. Based on the proposed quantitative method of building carbon emission, this paper establishes the quota theoretical system of building carbon emission analysis, and develops the quota based carbon emission calculation software. It provides a fast and effective calculation tool for the quantitative evaluation of carbon emission of construction projects, so as to realize the carbon emission control and Optimization in the early stage of architectural design and construction. On this basis, the evaluation, analysis and calculation method of building structure based on carbon reduction target is proposed, combined with the carbon emission quota management standard proposed in this paper. Taking small high-rise residential buildings as an example, this paper compares and analyzes different building structural systems from the perspectives of structural performance, economy and carbon emission level. It provides a reference for the design and evaluation of low-carbon building structures. The smart energy management system collects user energy use parameters. It uses time period and time sequence to obtain a large amount of data for analysis and integration, which provides users with intuitive energy consumption data. Compared with the traditional architectural design method, the industrialized construction method can save 589.22 megajoules (MJ) per square meter. Based on 29270 megajoules (MJ) per ton of standard coal, the construction area of the case is about 8000m2, and the energy saving of residential buildings is 161.04 tons of standard coal. The scheme designed in this study is an effective method to reduce the carbon emission intensity of buildings.

Influence of wind turbine structural parameters on wind shear and tower shadow effect

yajing Zhang, Zhi guo Li; chaoyang Song — Wed, 30 Nov 2022 00:00:00 +0800

To overcome the problems of decrease in power quality and eliminate the wind speed fluctuation due to wind shear and tower shadow effect arising from structural parameters of a wind turbine, an improved prediction model accounting for the dual effects of wind shear and tower shadow is built on the basis of conventional mathematical model for upwind wind turbines. Compared to the conventional prediction model, the proposed model contains a new constraint condition, which makes the disturbance term of incoming wind speed caused by tower shadow effect always negative so that the prediction result is closer to the actual situation. Furthermore, the influence of wind turbine structural parameters such as hub height, rotor diameter, diameter of tower top, and rotor overhang on wind shear and tower shadow effect are explored in detail. The results show that with the increase in hub height, the wind shear effect became more and more weak. The hub height is independent of tower shadow effect. The rotor diameter is positively correlated with the wind shear and tower shadow effect. The tower shadow effect is positively correlated with the diameter of tower top and negatively correlated with the rotor overhang.

Operation State of the Wind Turbine Pitch System Based on Fuzzy Comprehensive Evaluation

feng an zhu — Wed, 30 Nov 2022 00:00:00 +0800

To ensure safe wind turbine (WT) operations and improve the utilization rate of wind energy, effective evaluation of the operation state of the pitch system is critical. Therefore, a method was proposed to evaluate the operation state of the pitch system of WT based on fuzzy comprehensive evaluation. First, based on SCADA data, the working state of the pitch system under rated power state and power state of WT were analyzed. Second, through the analysis of characteristic parameters and physical mechanism of the pitch system, the consistency principle of characteristic parameters, the stability principle of power under rated state, and the stability principle of blade angle underpowered state were obtained. Next, based on the aforementioned principles, the evaluation indexes were established, and the fuzzy comprehensive evaluation method was used to establish the operation state evaluation model of the pitch system under rated power state and under power state of the WT. Finally, an example was provided to verify the effectiveness of the method. The evaluation model established in this study can be used as a technical reference for the online monitoring of WT pitch systems to ensure the safe and stable operation of WTs.

Research on Representative Engineering Applications of Anemometer Towers Location in Complex Topography Wind Resource Assessment

Hao Liu — Fri, 28 Oct 2022 00:00:00 +0800

The typical location and number of anemometer tower in the assessed area are the key to the accuracy in complex topography wind resource assessment. This paper took two typical complex topography wind farms in Guangxi, Yunnan province in China as calculation examples. Firstly, we simulated the wind resource status of the anemometer tower in the Meteodyn WT software. Secondly, we compared the simulated wind resource with the actual measured data by the anemometer tower in same situation. Thirdly, we analyzed the influence of anemometer tower location and quantity in the accuracy of wind resource assessment through the above comparison results. The results showed that the range which the anemometer tower can represent is limited (<5 kilometers), and the prediction error more than 5%. Besides, the anemometer towers in special terrain areas (such as wind acceleration areas) cannot be used as representative choice. The relative error of the simulated average annual wind speed by choose different number of anemometer towers is about 4%, and the grid-connected power generation more than 6%. The representative effect of anemometer towers is of great significance for increasing the accuracy of wind resource assessment in engineering application.

Coordinated rotor-side control strategy for Doubly-fed wind turbine under symmetrical and asymmetrical grid faults

YAN QUANCHUN — Fri, 28 Oct 2022 00:00:00 +0800

Aiming at the problems of rotor over-voltage, over-current and DC side voltage rise caused by grid voltage drops, a coordinated control strategy based on symmetrical and asymmetrical low voltage ride through of rotor side converter of doubly-fed generator is proposed. When the grid voltage drops symmetrically, the dynamic process of the stator current excitation is considered, and the depth of the voltage drop is detected according to the change of the stator flux linkage, so as to dynamically provide the corresponding reactive power support for the parallel network and accelerate the voltage recovery. When the grid voltage drops asymmetrically, the doubly-fed generator model is established in the positive and negative sequence rotating coordinate system. Considering the output voltage limit of the converter, the positive sequence current and negative sequence current of the rotor are suppressed respectively. The control module is designed to adapt to different types of power grid fault at the same time. Finally, the simulation model of doubly-fed wind turbine is constructed in Matlab / Simulink. The simulation results verify that the proposed control strategy can improve the low-voltage ride through performance of the system when dealing with the symmetrical and asymmetrical voltage drop of the power grid.

Time-domain Protection for Transmission Lines Connected to Wind Power Plant based on Model Matching and Hausdorff Distance

Hongchun Shu, Xiaohan Jiang, Pulin Cao, Na An, Xincui Tian, Bo Yang — Wed, 18 Nov 2020 00:00:00 +0800

The system impedance instability, high-order harmonics, and frequency offset are main fault characteristics of wind power system. Moreover, the measurement angle of faulty phase is affected by rotation speed frequency component, which causes traditional directional protections based on angle comparison between voltage and current to operate incorrectly. In this paper, a time-domain protection for connected to wind power plant based on model matching is proposed, which compares the calculated current and the measured current to identify internal faults and external faults. Under external faults, the calculated current and measured current waveform are quite similar because the protected transmission lines is equivalent to a lumped parameter model and the model itself is not damaged. However, the similarity of calculated current and measured current is quite low, due to destroyed integrity of model under internal faults. Additionally, Hausdorff distance is introduced to obtain the similarity of the calculated current and measured current. Since the proposed protection scheme is applied in time domain, it is independent from current frequency offsets of wind energy system, high-order harmonics, and system impedance variations. Comprehensive case studies are undertaken through Power Systems Computer Aided Design (PSCAD), while simulation results verify the accuracy and efficiency of the proposed approach in fault identification.

Model Predictive Yaw Control Using Fuzzy-deduced Weighting Factor for Large-scale Wind Turbines

Fri, 25 Dec 2020 00:00:00 +0800

Yaw control system plays an important role in helping large-scale horizontal wind turbines capture the wind energy. To track the stochastic and fast-changing wind direction, the nacelle is rotated by the yaw control system. Therein, a difficulty consists in the variation speed of the wind direction much faster than the rotation speed of the nacelle. To deal with this difficulty, model predictive control has been recently proposed in the literature, in which the previewed wind direction is employed into the predictive model, and the estimated captured energy and yaw actuator usage are two contradictive objectives. Since the performance of the model predictive control strategy relies largely on the weighting factor that is designed to balance the two objectives, the weighting factor should be carefully selected. In this study, a fuzzy-deduced scheme is proposed to derive the weighting factor of the model predictive yaw control. For the proposed fuzzy-deduced strategy, the variation degree and the increment of the wind direction during the predictive horizon are used as the inputs, and the weighting factor is the output, which is dynamically adjusted. The proposed model predictive yaw control is demonstrated by some simulations using real wind data and its performance is compared with the conventional model predictive control with the fixed weighting factor. Comparison results confirm the outweighing performance of the proposed control strategy over the conventional one.

Analysis of electromagnetic Performance of Modulated Coaxial Magnetic Gears Used in Semi-Direct Drive Wind Turbines

Liqun Qian, Jungang Wang, Shuairui Xu, Ruina Mo — Fri, 25 Dec 2020 00:00:00 +0800

风力涡轮机是实现风能利用的关键设备，受到了各国的高度评价。但是现有风力发电装置的机械齿轮传动具有振动和噪音大，故障率高，维修时间短的缺点。磁场调制电磁齿轮传动是一种新型的非接触式传动方法，具有无摩擦振动，无需润滑保养等优点。然而，常规的调制电磁齿轮具有低扭矩密度和具有大波动的扭矩缺陷。为了克服现有半直接驱动风力发电机械的齿轮传动问题，并改善传统电磁齿轮传动的电磁性能，本文提出了一种新的采用表面贴装Halbach阵列调制磁齿轮法代替机械齿轮传动的非接触半直驱风力发电机的新型传动方案，并考虑了半直驱调制磁发电机的电磁特性。风力涡轮机。利用有限元软件构建了表面安装的Halbach阵列电磁齿轮和常规齿轮的模型，分析了两个电磁齿轮的磁场线分布，计算了内部和外部空气的气隙磁通密度气隙，求出内部和外部气隙磁密度的主要谐波；计算模型中内转子和外转子的静态转矩和稳态运行转矩，比较气隙磁通密度，电磁齿轮的谐波和扭矩。仿真结果表明，表面贴装Halbach阵列电磁齿轮法的磁场调制式电磁齿轮改善了内，外气隙的磁感应波形，减小了脉冲转矩波动，并具有较高的静态转矩。将其应用于半直接驱动风力发电设备，不仅克服了机械齿轮的缺点，而且具有更高的电磁性能。因此，表面安装的Halbach阵列调制电磁齿轮可以代替半直接驱动风力发电设备中的机械齿轮箱。仿真结果表明，表面贴装Halbach阵列电磁齿轮法的磁场调制式电磁齿轮改善了内，外气隙的磁感应波形，减小了脉冲转矩波动，并具有较高的静态转矩。将其应用于半直接驱动风力发电设备，不仅克服了机械齿轮的缺点，而且具有更高的电磁性能。因此，表面安装的Halbach阵列调制电磁齿轮可以代替半直接驱动风力发电设备中的机械齿轮箱。仿真结果表明，表面贴装Halbach阵列电磁齿轮法的磁场调制式电磁齿轮改善了内，外气隙的磁感应波形，减小了脉冲转矩波动，并具有较高的静态转矩。将其应用于半直接驱动风力发电设备，不仅克服了机械齿轮的缺点，而且具有更高的电磁性能。因此，表面安装的Halbach阵列调制电磁齿轮可以代替半直接驱动风力发电设备中的机械齿轮箱。而且具有更高的电磁性能。因此，表面安装的Halbach阵列调制电磁齿轮可以代替半直接驱动风力发电设备中的机械齿轮箱。而且还具有较高的电磁性能。因此，表面安装的Halbach阵列调制电磁齿轮可以代替半直接驱动风力发电设备中的机械齿轮箱。

Adaptive Fractional-order PID Control for VSC-HVDC Systems via Cooperative Beetle Antennae Search with Offshore Wind Integration

Pulin Cao; Haoran Fan; Zilong Cai — Fri, 25 Dec 2020 00:00:00 +0800

Since the voltage source converter based high voltage direct current (VSC-HVDC) systems owns the features of nonlinearity, strong coupling and multivariable, the classical proportional integral (PI) control is hard to obtain content control effect. Hence, a new perturbation observer based fractional-order PID (PoFoPID) control strategy is designed in this paper for VSC-HVDC) systems with offshore wind integration, which can efficiently boost the robustness and control performance of entire system. Particularly, it employs a fractional-order PID (FoPID) framework for the sake of compensating the perturbation estimate, which dramatically boost the dynamical responds of the closed-loop system, and the cooperative beetle antennae search (CBAS) algorithm is adopted to quickly and efficiently search its best control parameters. Besides, CBAS algorithm is able to efficiently escape a local optimum because of a suitable trade-off between global exploration and local exploitation can be realized. At last, comprehensive case studies are carried out, namely, active and reactive power tracking, 5-cycle line-line-line-ground (LLLG) fault, and offshore wind farm integration. Simulation results validate superiorities and effectiveness of PoFoPID control in comparison of that of PID control and feedback linearization sliding-mode control (FLSMC), respectively.

Power data preprocessing method of mountain wind farm based on POT-DBSCAN

feng an zhu, zhao xiao, qiancheng zhao — Tue, 23 Mar 2021 00:00:00 +0800

Due to the frequent changes of wind speed and wind direction on mountain wind farms, wind turbine (WT) power prediction using traditional data preprocessing method results in low accuracy. This paper proposes a data preprocessing method which combines POT with DBSCAN (POT-DBSCAN) to improve the prediction efficiency of wind power prediction model. Firstly, the power prediction model of WT based on particle swarm optimization (PSO) arithmetic is combined with BP neural network (PSOBP) method is established according to the data of WT in the normal operation condition. Secondly, the wind-power data obtained from the supervisory control and data acquisition (SCADA) system is preprocessed by the POT-DBSCAN method. Then, the power prediction of the preprocessed data is carried out by PSOBP model. Finally, the necessity of preprocessing is verified by the indexes. The case analysis shows that the error obtained by PSOBP model without preprocessing is higher than the threshold, while the error of data preprocessing by POT-DBSCAN is lower than the threshold value and consistent with the actual operation of wind turbine, which verifies the effectiveness of the method.

Probabilistic Load Flow Calculation of Power System Integrated with Wind Farm based on Kriging Model

Xinglang Su, Lu Li; Yuzhen Fan, Gefei Qiu — Tue, 23 Mar 2021 00:00:00 +0800

Because of the randomness and uncertainty, integration of large-scale wind farms in a power system will exert significant influences on the distribution of power flow. This paper uses polynomial normal transformation method to deal with non-normal random variable correlation, and solves probabilistic load flow based on Kriging method. This method is a kind of smallest unbiased variance estimation method which estimates unknown information via employing a point within the confidence scope of weighted linear combination. Compared with traditional approaches which need a greater number of calculation times, long simulation time, and large memory space, Kriging method can rapidly estimate node state variables and branch current power distribution situation. As one of the generator nodes in the western Yunnan power grid, a certain wind farm is chosen for empirical analysis. Results are used to compare with those by Monte Carlo-based accurate solution, which proves the validity and veracity of the model in wind farm power modeling as output of the actual turbine through PSD-BPA.

Robust Variable-pitch Control Design of PMSG via Perturbation Observer

Yilin Hu; Yan Xie; Bo Li — Wed, 02 Jun 2021 00:00:00 +0800

Wind turbine employs pitch angle control to maintain captured power at its rated value when the wind speed is higher than rated value. This work adopts a perturbation observer based sliding-mode control (POSMC) strategy to realize robust variable-pitch control of permanent magnet synchronous generator (PMSG). POSMC combines system nonlinearities, parametric uncertainties, unmodelled dynamics, and time-varying external disturbances into a perturbation, which aims to estimate the perturbation via a perturbation observer without an accurate system model. Subsequently, sliding mode control (SMC) is designed to completely compensate perturbation estimation in real-time for the sake of achieving a global consistent control performance and improving system robustness under complicated environments. Simulation results indicate that, compared with vector control (VC), feedback linearization control (FLC), and nonlinear adaptive control (NAC), POSMC has the best control performance in ramp wind and random wind and the highest robustness in terms of parameter uncertainty.

Assessment of the Rural Water Supply Potential by Mechanical Wind Pumping Around the Flood Plains of Lake Chad

dieudonné kaoga kidmo, Bachirou Bogno, Michel Aillerie, kodji deli — Wed, 02 Jun 2021 00:00:00 +0800

In the present work, an assessment of the rural water supply potential by mechanical wind pumping around the flood plains of Lake Chad has been considered. Inside the floodplains around Lake Chad, available surface water is largely contaminated and represents health hazards to populations and access to underground and clean water has increasingly become rare. Moreover, clean water scarcity has led to conflict and territorial pressures, which are contributing factors to poverty in the considered area. Four localities, Baga, Baga-Sola, Makari and Nguigmi, respectively, in Nigeria, Chad, Cameroon and Niger have been selected inside the floodplains around Lake Chad, to evaluate the potential of wind power and prospects of windmills development to provide safe drinking-water supply, livestock watering and small-scale irrigation. Long-term satellite-derived data, obtained through the Prediction of Worldwide renewable Energy Resources have been considered suitable and viable alternative to missing site-specific data from ground stations. Windmill of Multi-blade driven piston pump is the preferred water pumping option for this study because of its higher overall system efficiency. The results of this study indicate that mean wind speeds, at 10 m height above ground level, are 4.64 m/s for Baga, 4.76 m/s for Baga-Sola, 4.32 m/s for Makari and 4.44 m/s for Nguigmi. In addition, wind speeds for Baga, for instance, are in the range of 2.5-10 m (working range of a wind pump), at 10, 15, 20 and 25 m height agl, for 79.64, 82.80, 84.79, and 86.19 per cent of the time. Corresponding values for Baga-Sola, Makari and Nguigmi are in the range of 80.50-87.76 per cent, 76.86-85,58 per cent, 77.92-86.21 per cent, respectively. For a Windmill with a 2 m-blade, a 25 m-height tower and considering a total dynamic head of 30 m, average monthly discharges for the dry season are 1,330, 1,374, 1,200 and 1,199 m³, respectively for Baga, Baga-Sola, Makari and Nguigmi. Furthermore, corresponding costs of water are 9.53, 9.23, 10.56 and 10.57 XAF/m³, for Baga, Baga-Sola, Makari and Nguigmi, in that order.

The multiobjective optimization of AFPM generators with double-sided internal stator structures for vertical axis wind turbines

song dan dan — Sat, 17 Jul 2021 00:00:00 +0800

The axial flux permanent magnet (AFPM) generator with double-sided internal stator structure is highly suitable for vertical axis wind turbines due to its high power density. The performance of the AFPM generator with double-sided internal stator structure can be improved by the reasonable design of electromagnetic parameters. To further improve the overall performance of the AFPM generator with double-sided internal stator structure, multivariable (coil width ω_c, permanent magnet thickness h, pole arc coefficient α_p and working air gap l_g) and multiobjective (generator efficiency η, total harmonic distortion of the voltage and induced electromotive force amplitude) functional relationships are innovatively established. Orthogonal analysis, mean analysis and variance analysis are performed on the influence parameters by combining the Taguchi method and response surface methodology to study the influence degrees of each influence parameter on the optimization objectives to determine the most appropriate electromagnetic parameters. The optimization results are verified by 3D finite element analysis. The optimized APFM generator with double-sided internal stator structure exhibits superior economy, stronger magnetic density, higher efficiency and improved power quality.

Analysis of near-wake deflection characteristics of horizontal axis wind turbine tower under yaw state

Zhen Liu, Jianwen Wang — Fri, 17 Sep 2021 00:00:00 +0800

The yaw of the horizontal axis wind turbine results in the deflection of the wake flow field of the tower. The reasonable layout of wind farm can reduce the power loss of the downstream wind turbine generators due to the blocking effect of the upstream wake flow and increase the output power of the whole wind farm. However, there is still much space for the further research. In this paper, experimental research is conducted on the near-wake deflection characteristics of wind turbine tower under yaw state, expecting the effect of throwing away a brick in order to get a gem. In the low-turbulence wind tunnel test, regarding the most unfavorable position where the rotating blades coincide with the tower, Particle image velocimetry (PIV) technology is used to test the instantaneous velocity field and output power and analyze experimental data at four different yaw angles, different inflow velocities and heights. Meanwhile, in order to quantitatively analyze the laws on wake deflection, the radon transformation is used to analyze the velocity contour for calculating the wake direction angle, and the results show high reliability. The comprehensive experimental results indicate that the near-wake flow field of the tower obviously deflects towards a side in the horizontal plane. With the increase of the yaw angle, the deflection angle of the wake flow field further increases, and the recovery of wake velocity accelerates. The change laws on the wake direction angle with the yaw angle and the blade spanwise direction are obtained. The experiment in this paper can provide guidance for layout optimization of wind farm, and the obtained data can provide a scientific basis for the research on performance prediction of horizontal axis wind turbine.

Optimal Configuration of Off-grid Hybrid Wind hydrogen Energy System : Comparison of Two Systems

Zekun Wang, Yan Jia, Yingjian Yang; Chang Cai; Yinpeng Chen — Fri, 17 Sep 2021 00:00:00 +0800

Due to the uncertainty of renewable energy power generation and the non-linearity of load demand, it becomes complicated to determine the capacity of each device in hybrid renewable energy power generation systems. This work aims to optimize the capacity of the two types of the off-grid hybrid wind-hydrogen energy system, considered the maximum profit of the system and the minimum loss of power supply probability. Firstly, we established steady-state models of the wind turbine, alkaline electrolyzer, lead-acid battery, and proton exchange membrane fuel cell in matrix laboratory software to optimize the capacity. Secondly, we analyzed the operating mode of the system and determined two system structures (the system contains batteries whether or not). Finally, according to the wind speed and load data in the calculation example area, the annual power generation of the system is estimated with the loss of power supply probability as the constraint condition. In the same calculation example data, the non-dominated sorting genetic algorithm-II is used to optimize the capacity of each device in the two systems. The result showed that the profit of a without a battery-equipped system is 32.38% higher than another system. But the power supply reliability is the opposite. To avoid the contingency of the calculation results, we used a genetic algorithm and ant colony optimization to calculate the same example. This paper provided two schemes for the optimal configuration of the hybrid wind-hydrogen energy system in islanding mode, which provided a theoretical basis for practical engineering applications.

Enhanced Atom Search Optimization based Optimal Control Parameter Tunning of PMSG for MPPT

Xin He, Ping Wei, Xiaoyan Gong; Xiangfei Meng, Dong Shan; Jiawei Zhu — Sat, 04 Dec 2021 00:00:00 +0800

For the past few years, wind energy is the most popular non-traditional resource among renewable energy resources and it’s significant to make full use of wind energy to realize a high level of generating power. Moreover, diverse maximum power point tracking (MPPT) methods have been designed for varying speed operation of wind energy conversion system (WECS) applications to obtain optimal power extraction. Hence, a novel and meta-heuristic technique, named enhanced atom search optimization (EASO), is designed for a permanent magnet synchronous generator (PMSG) based WECS, which can be employed to track the maximum power point. One of the most promising benefits of this technique is powerful global search capability that leads to fast response and high-quality optimal solution. Besides, in contrast with other conventional meta-heuristic techniques, EASO is extremely not relying on the original solution, which can avoid sinking into a low-quality local maximum power point (LMPP) by realizing an appropriate trade-off between global exploration and local exploitation. At last, simulations employing two case studies through Matlab/Simulink validate the practicability and effectiveness of the proposed techniques for optimal proportional-integral-derivative (PID) control parameters tuning of PMSG based WECS under a variety of wind conditions.

Protection of zero-sequence power variation in mountain wind farm collector lines based on multi-mode grounding

Yaqi Deng — Mon, 24 Jan 2022 00:00:00 +0800

The arc-suppression coil (ASC) in parallel low resistance (LR) multi-mode grounding is adopted in the mountain wind farm to cope with the phenomenon that is misoperation or refusal of zero-sequence protection in LR grounding wind farm. If the fault disappears before LR is put into the system, it is judged as an instantaneous fault; while the fault does not disappear after LR is put into the system, it is judged as a permanent fault; the single-phase grounding (SLG) protection criterion based on zero-sequence power variation is proposed to identify the instantaneous-permanent fault. Firstly, the distribution characteristic of zero-sequence voltage (ZSV) and zero-sequence current (ZSC) are analyzed after SLG fault occurs in multi-mode grounding. Then, according to the characteristics that zero-sequence power variation of non-fault collector line is small, while the zero-sequence power variation of fault collector line can reflect the active power component of fault resistance, the protection criterion based on zero-sequence power variation is constructed. The theoretical analysis and simulation results show that the protection criterion can distinguish the property of fault only by using the single terminal information, which has high reliability.

Research on the Impacts of the Inertia and Droop Control Gains from a Variable-Speed Wind Turbine Generator on the Frequency Response

Mon, 24 Jan 2022 00:00:00 +0800

System frequency must be kept very close to its nominal range to ensure stable of an electric power grid. Excessive system frequency variations are able to result in load shedding, frequency instability, and even generator damage. With the increasing wind power penetration, there is rising concern about the reduction in inertia response and primary frequency control in the electric power grid. Converter-based wind generation is capable of providing inertia response and primary frequency response; nevertheless, primary frequency and inertia responses of wind generation are different from those of conventional synchronous fleets, which is not completely understood how the primary frequency and inertia responses affect the system at various disturbances and available kinetic energy levels. Simulation works investigate the influences of the inertia and droop control strategies on the dynamic frequency response under various disturbances and wind conditions, particularly the index of second frequency drop. Quantitative analysis provides insight to setting the inertia and droop control coefficients for various wind and disturbance conditions to facilitate adequate dynamic frequency response during frequency events.

A Preliminary Feasibility Study of a Novel Low Speed Wind Turbine Application in Africa

Kehinde Adeseye Adeyeye, Nelson Ijumba, Jonathan Colton — Fri, 01 Apr 2022 00:00:00 +0800

: This paper posits that a low-speed wind turbine design would be suitable for harnessing wind energy in Africa. Conventional wind turbines consisting of propeller designs are commonly used across the world. A major hurdle to utilizing wind energy in Africa is that conventional commercial wind turbines are designed to operate at wind speeds greater than those prevalent in most of the continent, especially in sub-Sahara Africa (SSA). They are heavy and expensive to purchase, install, and maintain. Only a few countries in Africa have been able to include wind energy in their energy mix. In this paper, the feasibility of a novel low-speed wind turbine designed based on the Ferris wheel for low wind speed application in Africa is demonstrated. The performance of Ferris wheel wind turbines (FWT) with 61 m (200 ft), 73 m (240 ft) and 104 m (341 ft) diameter rims and an 800 kW generator are evaluated for some selected African cities. The research also compares the Weibull wind distribution of the African cities of interest. A comparison between the FWT and the conventional commercial wind turbines in terms of efficiency, rated wind speed, cost, performance, and power to weight is performed. Results show that the FWT has the potential for economic power generation at rated wind speeds of 6.74 m/s, which are lower than the average of 12 m/s for conventional wind turbines, and lower power to weight ratios of 5.2 kW/tonne.

Optimization Design of the Bionic Bamboo Tower for Wind Turbine

Fugang Dong, Yuqiao Zheng, Hao Li, Zhengwen He — Fri, 01 Apr 2022 00:00:00 +0800

This work takes the bionic bamboo tower (BBT) of 2MW wind turbine as the target, and the non-dominated sorting genetic algorithm (NSGA-Ⅱ) is utilized to optimize its structural parameters. Specifically, the objective functions are deformation and mass. Based on the correlation analysis, the target optimization parameters were determined. Furthermore, the Kriging model of the BBT was established through the Latin Hypercube Sampling Design (LHSD). Finally, the BBT structure is optimized with multiple objectives under the constraints of strength, natural frequency, and size. The comparison shows that the optimized BBT has an advantage in the Design Load Case (DLC). This advantage is derived from the overall stability of the BBT is increased by 2.45% while the displacement is reduced by 0.77%. In addition, the mass of the tower is decreased by 1.49%. Correspondingly, the steel consumption of each BBT will be reduced by 2789Kg. This work provides a scientific basis for the structural design of the tower in service.

Study on the Flow Mechanism of Wind Turbine Blades under the Yawed Condition

Shuang Zhao — Mon, 23 May 2022 00:00:00 +0800

The Computational Fluid Dynamics method was used to simulate the flow field around the wind turbine at the yaw angles of 0°, 15°, 30° and 45°. The angle of attack and the relative velocity of the spanwise sections of the blade were extracted with the reference-points method. By analyzing the pressure distribution and flow characteristics of the blade surface, the flow mechanism of the blade surface under yaw conditions was discussed. The results showed that the variation of the angle of attack and relative velocity were related to the azimuth angle and radius under yawed condition. The larger the yaw angle was, the larger the variation was. The pressure distribution at the spanwise sections was affected by both the angle of attack and relative velocity. The angle of attack was more influential. At the same yaw angle, when the angle of attack decreased, c_p curve shrunk inward and lift force decreased. The larger the yaw angle was, the more obvious the shrink was. The effect of yaw on blade root was higher than blade tip.

Control System Design for Low Power Magnetic Bearings in a Flywheel Energy Storage System

Matthew Owen Thomas Cole, Tinnawat Hongphan, Chakkapong Chamroon, Ziv Brand — Fri, 28 Oct 2022 00:00:00 +0800

This paper deals with the feedback controller design problem for active magnetic bearings (AMBs) in a small-scale flywheel energy storage system. A benchmark control implementation involving PD (proportional-derivative) feedback of rotor displacement measurements is first considered. This type of controller can stabilize the rotor suspension for low rotational speeds but cannot achieve low energy consumption. Moreover, without additional compensation, the nutation mode of the flywheel rotor becomes unstable at high speeds, leading to severe vibration. To achieve the goals of low energy consumption and improved stability, a frequency-domain design approach based on H-infinity control optimization is introduced. Through the choice of design weighting functions, notch filter characteristics are incorporated within the controller to reduce AMB current components caused by rotor vibration at the synchronous frequency and higher harmonics. Experimental tests are used to validate the controller design methodology and provide comparative results on performance and efficiency. According to test findings, the H-infinity controller is able to achieve stable rotor levitation and reduce AMB power consumption by more than 40 % (from 4.80 Watts to 2.64 Watts) compared with the conventional PD control method. Additionally, the H-infinity controller can prevent vibrational instability of the rotor nutation mode, which is prone to occur when operating with high rotational speeds.

Hydroprocessing and Blending of a Biomass-Based DtG-Gasoline

David Graf, Philipp Neuner, Reinhard Rauch — Wed, 14 Sep 2022 00:00:00 +0800

The number of annually registered internal combustion vehicles still exceeds electric-driven ones in most regions, e.g., Germany. Ambitious goals are disclosed with the European Green Deal, which calls for new technical approaches and greenhouse gas-neutral transition technologies. Such bridging technologies are synthetic fuels for the transportation sector, e.g., utilizing the bioliq^® process for a CO₂-neutral gasoline supply. Fuels must meet the applicable national standards to be used in existing engines. Petrochemical parameters can be variably adapted to their requirements by hydroprocessing. In this work, we considered the upgrading of aromatic-rich DtG gasoline obtained from the bioliq^® process. The heavy gasoline was therefore separated from the light one by rectification. We investigated how to selectively modify the petrochemical parameters of the heavy gasoline, especially the boiling characteristics, to make the product suitable as a high-quality blending component. Three commercially available Pt/zeolite catalysts were tested over a wide range of temperature and space velocity. We achieved high gasoline yields, while the content of light end compounds up to a boiling temperature of 150 °C could be increased significantly. In contrast to the high molecular naphthenic character of the gasoline, the octane number obtained was satisfactory. Especially the Motor Octane Number turned out unexpectedly high and showed a dependency on the isomerization of the naphthenic rings. By blending the upgraded heavy gasoline with the previously separated light gasoline, we could finally show that hydroprocessing is suitable for adjusting petrochemical parameters. The aromatics concentration was 37.5 % lower than in the original raw gasoline, while the boiling characteristics improved significantly. Additionally, the final boiling point was 82 °C lower, which will be beneficial when it comes to the expected emission behavior.

Performance on Power, Hot and Cold Water Generation of a Hybrid Photovoltaic Thermal Module

Thu, 21 Jul 2022 00:00:00 +0800

This paper proposed a new function of photovoltaic thermal (PVT) module to produce nocturnal cool water not just only generating electrical power and hot water during daytime. Experimental tests were carried out under Chiang Mai tropical climate with a 200 Wp monocrystalline PVT module having dimensions of 1.601 m x 0.828 m connected with two water tanks each of 60 L taken for hot and cool water storages. The module was facing south with 18^o inclination. The electrical load was a 200 W halogen lamp.

It could be seen that within 4 consecutive days by taking the module as a nocturnal radiative cooling surface, the cool water temperature in the storage tank was lower than the ambient temperature in early morning. The cool water was used to cool down the PVT module from noon and higher electrical power could be achieved. A set of mathematical models was also developed and the simulated results on the PVT module temperature and the hot water temperature including the nocturnal cool water temperature in the storage tanks agreed well with the experimental data. For a big scale such as solar farms, high amount of nocturnal cool water could be generated and it was recommended to use for space cooling during daytime.

Production of Producer Gas from Densified Agricultural Biomass in Downdraft Gasifier and Its Application to Small Diesel Engines

KITTIKORN SASUJIT, Nigran Homdoung, Nakorn Tippayawong — Thu, 21 Jul 2022 00:00:00 +0800

Biomass is becoming one of the most popular renewable energy sources, especially from agricultural wastes. These wastes can be gasified and utilized in various industries. This experimental study investigated producer gas generation from densified agricultural fuels such as corncobs, rice husks, wood chips, and oil palm fronds in a 50kW_th throatless downdraft gasifier. This system produced combustible gases such as H₂, CO, and CH₄, which were utilized as a substitute for diesel fuel in a small diesel engine for power generation. The results showed that the gasifier performs successfully and seems to prefer pellets to briquettes. Producer gas contains 18-20% carbon monoxide, 1-6% hydrogen, and 0.9-1.9% methane. Maximum gasification efficiencies of 69-73% were achieved with biomass pellets from wood chips, corncobs, oil palm fronds, and rice husks, with the producer gas having a calorific value of 12-16 MJ/Nm³. The fuel consumption rate was between 15-16 kg/h, while the producer gas yield was between 2-3 Nm³/kg. The gravimetric concentration of biomass tar in the raw product gas was found to be in the range of 18-45 g/Nm³, in which pelletized fuel appeared to show slightly lower tar than briquette fuel. The tar was primarily composed of five compounds: Benzo (a) pyrene, chrysene, pyrene, phenanthrene, 1-methylnaphthalene, and several other polycyclic aromatic compounds. The producer gas from oil palm frond briquettes and biodiesel were tested in a gas engine system in a dual fuel mode. A thermal efficiency of 22.21% was achieved with 2500 W electric load and a 72% biodiesel displacement rate, respectively.

Energy Consumption Analysis and Characterization of Aerospace Manufacturing Facilities in the United States

khaled Bawaneh, Bradely Deken, Author, Amin Esmaeili, Dr — Fri, 28 Oct 2022 00:00:00 +0800

Abstract: In this study, previously published information on energy use in the U.S. aerospace manufacturing sector has been analyzed and then represented as energy intensities (MJ/ft²). Public sources were identified and aggregated to determine the energy usage of aerospace manufacturing facilities within the United States. From this dataset, a sample of 28 buildings were selected and the energy intensity for each building was estimated from the data and then analyzed. Next, as a part of this study, the energy data for three additional aerospace manufacturing facilities in the U.S. were collected firsthand. That data was analyzed and then compared with the energy intensities of the 28 buildings in the sample. Three different indicators of energy consumption in aerospace manufacturing facilities were used as comparators. These comparators are valuable to assist facility managers in determining potential energy savings and help in the decision-making process. On average, aerospace manufacturing facilities in the United States spent 4 cents for each dollar of sale on energy. The energy intensity (MJ/ft²) and the power intensity (W/ft²) for each facility were calculated based on the actual facility energy bills. The power intensity for these facilities ranges from 7 W/ft² to 13.5 W/ft². The energy intensity ranged from 21 MJ/ft² to 284 MJ/ft². We found that the power intensity was a good estimator for energy consumption when the annual operating hours are considered. Furthermore, this can be used to estimate energy-related carbon dioxide emissions.

Location and Capacity Determination Method of Electric Vehicle Charging Station Based on Simulated Annealing Immune Particle Swarm Optimization

jiulong Sun, Yanbo Che, Yibin Cai — Wed, 30 Nov 2022 00:00:00 +0800

Considering the construction and maintenance of the charging station, the distribution network loss of the charging station, and the economic loss on the user side of the electric vehicle, this paper takes the node and capacity of charging station planning as control variables and the minimum cost of system comprehensive planning as objective function, and thus proposes a location and capacity planning model for the electric vehicle charging station. Based on the problems of low efficiency and insufficient global optimization ability of the current algorithm, the simulated annealing immune particle swarm optimization algorithm(SA-IPSO) is adopted in this paper. The simulated annealing algorithm is used in the global update of the particle swarm optimization(PSO), and the immune mechanism is introduced to participate in the iterative update of the particles, so as to improve the speed and efficiency of PSO. Voronoi diagram is used to divide service area of the charging station, and a joint solution process of Voronoi diagram and SA-IPSO is proposed. By example analysis, the results show that the optimal scheme corresponding to the optimization method proposed in this paper has a low comprehensive cost, short charging waiting time, and 71.93 % utilization rate of the charger. Simulation comparison verifies that the improved algorithm has strong global ergodicity and high computational efficiency.

Diffusion of a Nonvolatile Fuel Spray in Swirl Flow

yanju wei — Wed, 18 Nov 2020 00:00:00 +0800

The combustion process of internal combustion engine is greatly influenced by the swirl flow in combustion chamber, especially for diesel engines, where the diesel diffusion process in the swirl field is vital for combustion efficiency and the formation of pollutants including nitric oxides and particulate matter. However, the spray diffusion process has not been lucubrated due to the difficulties of direct observation and the characterization of the internal flows in engine chamber. In this paper, a rapid compression machine (RCM) with an optical combustion chamber was established having the mean compression velocity of 7.55 m/s, compression pressure of 1.6 MPa, and an initial swirl ratio of 5.8. Three kinds of flow fields, including intense swirl field, weak swirl field and turbulent field, were created to investigate the diffusion characteristics of injected fuel. The experimental results show that, the blending of fuel and air consists of four stages: fuel injection, wall approaching, rapid diffusion and final diffusion. The fuel spray is firstly bended by the lateral flow of the swirl field, then liquid fuel is blown onto, and coats on, the sidewall. The fuel on the sidewall is finally enrolled into the chamber plenum afterwards in gaseous phase via the spiral arms (in swirl fields) and random routes (in turbulent field), and at last the fuel disperses all over chamber. The results give an intuitive observation and help better understand the air-fuel mixing process in diesel and direct inject gasoline engines.

A Research on Stability Control Strategy of Distributed-drive Electric Vehicle Based on Direct Yaw Moment Control

Shu Wang, Xianyong Gui; Haichuan Zhang — Wed, 02 Jun 2021 00:00:00 +0800

Combined with the characteristics of the distributed-drive electric vehicle and direct yaw moment control, a double-layer structure direct yaw moment controller is designed. The additional yaw moment controllers based on the model predictive control and the "feedforward + feedback" control are designed respectively. Taking the minimum utilization of tire adhesion as the optimization objective, the working characteristics of motor system and braking system as the constraints, the quadratic programming active set is designed to optimize the distribution of the additional yaw moment. The road surface adhesion coefficient have a great impact on the reliability of direct yaw moment control, for which joint observer of vehicle state parameters and road surface parameters is designed by using unscented Kalman filter algorithm, which correlates vehicle state observer and road surface parameter observer to form closed-loop feedback correction. The results show that, compared to the "feedforward + feedback" control, the vehicle's error of yaw rate and sideslip angle, under the control of the model predictive controller, is smaller, which can improve the vehicle stability effectively. In addition, according to the results of the docking road simulation test, the joint observer of vehicle state and road surface parameters can improve the adaptability of the vehicle stability controller to the road conditions with variable adhesion coefficients.

Kalman Filter Estimation of Lithium Battery SOC Based on Model Capacity Updating

Min Deng, Quan Min, Ge Yang, Man Yu — Mon, 24 Jan 2022 00:00:00 +0800

High-precision estimation of lithium battery SOC can effectively optimize vehicle energy management, improve lithium battery safety protection, extend lithium battery cycle life, and reduce new energy vehicle costs. In order to further improve the SOC estimation accuracy of lithium battery, the Singular Value Decomposition-Unscented Kalman Filter (SVD-UKF) based lithium battery SOC estimation algorithm with model capacity update is proposed based on the recursive least square method with forgetting factor (FRLS), Thevenin equivalent circuit model and SVD-UKF algorithm. Firstly, the application of the least squares method with forgetting factor in the parameter identification of Thevenin model is studied. At the same time, in order to overcome the shortcomings of Kalman filter linearization error and non-positive definite covariance matrix, the singular value decomposition unscented Kalman filter algorithm is proposed. Finally, in order to consider the impact of battery available capacity attenuation on the estimation of lithium battery SOC, the model capacity update algorithm is used to optimize the model parameters and state joint estimation algorithm based on FRLS & SVD-UKF. Verified by simulation and lithium battery test, the results show that the SVD-UKF algorithm based on model capacity update can accurately estimate the SOC of lithium battery in real time with the available capacity of lithium battery continuous attenuation, and the maximum absolute error is less than 3%. The purpose of improving the accuracy of SOC estimation of lithium batteries is achieved.

Research on MPPT of Photovoltaic Power Generation Based on CSA-INC Algorithm

shan wang — Fri, 28 Oct 2022 00:00:00 +0800

Due to the complex environment of the photovoltaic (PV) field, the photovoltaic array will be blocked and affected by partial shadows in actual operation, which will cause multiple peaks in the photovoltaic output characteristics. Existing maximum power point tracking (MPPT) methods have low tracking efficiency and poor stability under partial shading conditions (PSC). It is easy to fall into the local maximum power point, which will cause the output power quality to decrease. A photovoltaic array MPPT algorithm based on the fusion of the Cuckoo Search Algorithm (CSA) and incremental conductance (INC) algorithm is proposed to solve the above problem. Firstly, we use the efficient global search capability of CSA to quickly track to the global Maximum Power Point (MPP). Secondly, we introduce the conductance increment algorithm and use the INC good local search and fast convergence characteristics to track Maximum Power Point. In this paper, the two algorithms are simulated under partial conditions and sudden light intensity. Comparing the simulation results of the CSA and CSA-INC algorithm, it is found that the CSA-INC algorithm is faster than the CSA algorithm in tracking speed, with more minor errors and smaller steady-state fluctuations, which improves the output efficiency and power quality of the photovoltaic array.

Energy Demand Model for Forecasting Electricity in Oman Power Grid

Kenneth E Okedu, Ahmed Al-Abri — Wed, 30 Nov 2022 00:00:00 +0800

In modern smart power grids, energy demand for accurate forecasting of electricity is gaining attention lately as a major component with increasing interest of research. This is due to the fact that a good energy demand forecast would lead to proper responses for electricity demand. In addition, proper energy demand forecast would ensure efficient planning of the electricity industry and is critical in the scheduling of the power grid capacity and management of the entire power network. As most power systems are been deregulated and with the rapid introduction and development of smart-metering technologies in Oman, new opportunities may araise considering the efficiency and reliability of the power system, like price-based demand response programs. These programs could be either at a large scale for household, commercial and industrial users. However, excellent demand forecasting models are crucial for the deployment of these smart metering in the power grid. Consequently, in this paper, energy demand forecast in Oman is presented, using the econometric model to forecasts the energy and peak demand by econometric analysis. The energy econometric analysis describes the relationship between the growth of historical electricity consumption and macro-economic parameters (by region, and by tariff), considering a case study of Mazoon Electricity Distribution Company (MZEC), which is one of the major power distribution companies in Oman, for effective energy demand in the power grid. Furthermore, the Oman regulatory regime, financial mechanism, price control, distribution system security standard, and demand forecast were some of the areas addressed in this work.

A Weighted Combination Forecasting Model for Power Load Based on Forecasting Model Selection and Fuzzy Scale Joint Evaluation

Bingbing Chen, Zhengyi Zhu, Xuyan Wang, Can Zhang — Sat, 17 Jul 2021 00:00:00 +0800

To solve the medium and long term power load forecasting problem, the combination forecasting method is further expanded and a weighted combination forecasting model for power load is put forward. This model is divided into two stages which are forecasting model selection and weighted combination forecasting. Based on Markov chain conversion and cloud model, the forecasting model selection is implanted and several outstanding models are selected for the combination forecasting. For the weighted combination forecasting, a fuzzy scale joint evaluation method is proposed to determine the weight of selected forecasting model. The weighted combination forecasting results of the power consumption in a certain area of China show that the forecasting indexes (percentage error and mean absolute percentage error) are improved significantly compared with the single forecasting models.

Open-Circuit Faults Diagnosis in Direct-Drive PMSG Wind Turbine Converter

Wei Zhang, Qihui Ling, Qiancheng Zhao, Hushu Wu — Sat, 17 Jul 2021 00:00:00 +0800

Condition monitoring and fault diagnosis have been identified as the key to achieving higher availabilities of wind turbines currently. Numerous studies show that the insulated gate bipolar transistor (IGBT) open-circuit faults are a significant contributor to the failures of wind turbine converter. However, the multiple faults combinations and the influence of wind speed changes abruptly, grid voltage sags and noise interference have brought great challenges to IGBT open-circuit faults diagnosis. Accordingly, concerning IGBT open-circuit faults in direct-driven permanent magnet synchronous generator (PMSG) wind turbine converters, a diagnostic method for multiple open-circuit faults is proposed in this paper, which is divided into two tasks: the first one is the fault detection and the second one is the fault localization. The detection method is based on the relative current residuals after exponential transformation and on an adaptive threshold, and the localization method is based on the average values of fault phase currents. The scheduled diagnosis method is available to both the generator-side converter (GESC) and the grid-side converter (GRSC), allowing to detect and locate single and double IGBT open-circuit faults. For validating this, robustness test and multiple open-circuit faults diagnosis are presented in a 2-MW direct-driven PMSG wind turbine system, the results validate the reliability and effectiveness of the proposed method.

Load forecasting of the power system: An investigation based on the method of random forest regression

Fuyun Zhu, Guoqing Wu — Sat, 18 Sep 2021 00:00:00 +0800

Accurate power load forecasting is an important prerequisite for power dispatching and security of grid. In this paper, a mathematical model for power load forecasting based on the random forest regression was established. The input parameters of RFR model were determined by means of the grid search algorithm. The prediction results for several other common machine learning methods were compared with those for the established model. The result showed that the coefficient of determination (R²) of test set based on RFR model was the highest, reaching 0.514 while the corresponding mean absolute error (MAE) and the mean squared error (MSE) were the lowest. Besides, the impacts of the air conditioning system used in summer on the power load was discussed. The calculation results showed that the introduction of indexes in HVAC could improve the prediction accuracy of test set.

The Use of Single-phase Immersion for Cooling Data Center

Nugroho Agung Pambudi — Sat, 04 Dec 2021 00:00:00 +0800

Data centers are recognized as one of the most important aspects of the Fourth Industrial Revolution since conventional data centers are energy inefficient having depended on high power consumption, in which the cooling is responsible for 40% of the usage. Therefore, this research proposes an immersion cooling technology as one of the solutions to solve the existing cooling problem. This will be achieved by using two types of dielectric fluid in evaluating a single-phase immersion cooling. In addition, flow rates and fan rotation are two variables that will also be investigated. Mineral and Virgin Coconut Oil (VCO) are the two dielectric fluids used to submerge the processor, motherboard, and power supply unit in a container. Benchmark software was adopted to obtain the maximum work of the CPU with the temperature data performed for 24 hours. The inflow and outflow temperatures were recorded using a data logger. The results of this study indicate that immersion cooling can reduce the temperature by 13°C lower than the conventional cooling method. The most optimum variable used to decrease the temperature was 1.5 lpm of flow rate and 800 rpm of fan rotation. Furthermore, the cooling performance of the two dielectric fluids shows that the mineral oil is better than the Virgin Coconut Oil (VCO).

Multifunction Battery Energy Storage System for Distribution Networks

Omar H. Abdalla, Gamal Abdel-Salam, Dr., Azza A. A. Mostafa — Mon, 24 Jan 2022 00:00:00 +0800

Battery Energy Storage System (BESS) is one of the potential solutions to increase energy system flexibility. As BESS is well suited to solve many challenges in transmission and distribution networks. In this paper, BESS is used to support distribution network in reconfiguration after fault, increasing Photovoltaic (PV) penetration, cutting peak load, and load valley filling. During fault, reconfiguration is used to supply loads but load disconnection might happen due to technical constraints violation. With PV penetration, distribution networks suffer from unpredictable power generation change, which affects the network performance. For determining the maximum power generation change due to PV, actual power registration of connected PV plants in South Cairo Electricity Distribution Company (SCEDC) was considered for a year. The paper presents a methodology for BESS optimal location and sizing considering technical constraints during reconfiguration after a fault and PV power generation changes. In addition, the paper provides a procedure for distribution network operator to employ the proposed BESS to perform multi functions such as ability to absorb PV power surplus, cut peak load and fill load valley for improved network's operation. The methodology is applied to a part of a district in SCEDC network consisting of 158 nodes. The simulation studies are performed using the DIgSILENT PowerFactory software and DPL programming language. The Mixed Integer Linear Programming optimization technique (MILP) in MATLAB is employed to choose the best location and sizing of BESS.

How Load Aggregators Avoid Risks in Spot Electricity Market: In the Framework of Power Consumption Right Option Contracts

jiacheng yang, Xiaohe Zhai, Zhongfu Tan, Zhenghao He — Fri, 01 Apr 2022 00:00:00 +0800

There is uncertainty in the electricity price of spot electricity market, which makes load aggregators undertake price risks for their agent users. In order to allow load aggregators to reduce the spot market price risk, scholars have proposed many solutions, such as improving the declaration decision-making model, signing power mutual insurance contracts, adding energy storage and mobilizing demand-side resources to respond. In terms of demand side, calling flexible demand-side resources can be considered as a key solution. The user’s power consumption rights (PCRs) are core contents of the demand-side resources. However, there have been few studies on the pricing of PCR contracts and transaction decisions to solve the problem of price forecast deviation and to manage the uncertainty of spot market prices. In addition, in traditional PCR contracts, PCRs are mostly priced using a single price mechanism, that is, the power user is compensated for part of the electricity that was interrupted or reduced in power supply. However, some power users might engage in speculative behaviours under this mechanism. Further, for load aggregators, their price risk avoidance ability has not substantially improved. As a financial derivative, options can solve the above problems. In this article, firstly, the option method is used to build an option pricing optimization model for power consumption right contracts that can calculate the optimal option premium and strike price of option contracts of power consumption rights. Secondly, from the perspective of power users and load aggregators, a simulation model of power consumption right transaction decision-making is constructed. The results of calculation examples show that (1) Under the model in this article, the pricing of option contracts for power consumption rights with better risk aversion capabilities than traditional compensation contracts can be obtained. (2) The decision to sell or purchase the power consumption rights will converge at respective high-value periods, and option contracts will expedite the process. (3) Option contracts can significantly reduce the loss caused by the uncertainty of spot electricity prices for load aggregators without reducing users' willingness to sell power consumption rights.

An Improved Immune Clone Selection Algorithm for Parameters Optimization of Marine Electric Power System Stabilizer

Zong Bi — Fri, 01 Apr 2022 00:00:00 +0800

In the marine electric power system, the marine generator will be disturbed by the large change of loads or the fault of power system. The low frequency oscillation caused by this may cause the instability of marine generator. Power system stabilizer (PSS) is used to suppress low frequency oscillation in marine electric power system. The parameters optimization method of power system stabilizer is studied. The typical PSS implementation type of leader-lag link was adopted, and the objective function was set in the optimization process. An improved immune clone selection algorithm (IICSA) for marine electric power system stabilizer parameters optimization is presented in this paper. Based on the basic immune clone selection algorithm (ICSA), adaptive incentive degree, vaccination and adaptive mutation strategies were adopted. The IICSA is used for the marine electric power system stabilizer optimization under load change disturbance and short-circuit fault cases. Through the simulation results, IICSA can ensure better convergence rate and higher convergence accuracy. After optimization of power system stabilizer parameters by IICSA, the ability of suppressing low-frequency oscillation of marine electric power system is increased. The stability of marine electric power system to control disturbances is enhanced.

Power Quality Assessment Based on Rough AHP and Extension Analysis

Guofeng Liu, Can Zhang, Zhengyi Zhu, Xuyan Wang — Fri, 01 Apr 2022 00:00:00 +0800

With the rapid development of economy and the gradual improvement of people's living standards, the power consumption of the whole society is increasing, and various new non-linear and asymmetric electrical equipment have been widely used. The power quality assessment problem in the new period has attracted attention. The mathematical essence of comprehensive assessment of power quality is a multi-attribute optimal decision-making problem. In order to solve the key problem of determining the indicator weight in the process of power quality assessment, a rough analytic hierarchy process (AHP) is proposed to aggregate the judgment opinions of multiple experts and eliminate the subjective effects of single expert judgment. Due to the advantage of extension analysis for solving the incompatibility problem, extension analysis method is adopted to assess the power quality. The assessment grades of both total power quality and each assessment indicator are obtained by correlation function. Through a case of 110kV bus of a converting station in a wind farm of China, the feasibility and effectiveness of the propose method are demonstrated. The result shows that the proposed method can determine the overall power quality of power grid and compare the differences among the performance of assessment indicators. The basis for further improving the power quality of power grid is also provided.

A New Proximity Indicator for assessment of voltage stability and critical loadability point

Chandrakant Dondariya — Fri, 01 Apr 2022 00:00:00 +0800

This paper presents a newly developed proximity indicator for voltage stability assessment which can be used to predict critical real system load and voltages at various load buses at critical loading point. Simulation is based on load flow equations and system real and reactive loadings have been increased in proportion with base case scenario for IEEE 14 and IEEE 25 bus test systems to demonstrate the behaviour of proposed proximity indicator. The proximity indicator varies almost parabolic with total real load demand and reach orthogonally to real load axis. This relation has been utilised to predict critical loading point. Most critical buses have been identified with simulation results obtained .CPF has been used as benchmark to check the accuracy of estimation. It has been shown that two operating points are needed for estimating critical point and proper selection of operating points and variation of proximity indicator near collapse point highly affect the accuracy of estimation.

Grid connected control strategy of VSG under complex grid voltage conditions

Bin Zhang, Yanjun Jin — Mon, 23 May 2022 00:00:00 +0800

Under complex grid conditions, the grid voltage usually has imbalance, low order harmonics and a small amount of DC bias. When the grid voltage contains low order harmonics and a small amount of DC bias component, the output current of the inverter can not meet the requirements of grid connection, and there is three-phase current imbalance in the control strategy of common VSG under unbalanced voltage. A theoretical analysis of non-ideal power grids is carried out, and a VSG control strategy under complex operating conditions is proposed. Firstly, the third-order generalized integrator (TOGI) is used to eliminate the influence of DC component of grid voltage. Based on the method of common VSG positive and negative sequence separation to control the balance current and power fluctuation under unbalanced voltage, an improved DSC (delay signal cancellation) method is proposed to eliminate the harmonic of command current, Then, the improved quasi proportional resonant controller (QPR) cascaded PI is used to further suppress the harmonic current, so that the harmonic content of grid connected current can meet the grid connected requirements and the three-phase current balance can be achieved. Finally, the proposed strategy is verified by simulation under the control objectives of current balance, active power and reactive power constant.

A Distributionally Robust Optimal Dispatch of Virtual Power Plant Based on Moment of Renewable Energy Resource

Wenlu Ji, Yong Wang, Xing Deng, Ming Zhang, Ting Ye — Thu, 21 Jul 2022 00:00:00 +0800

Virtual power plants can effectively integrate different types of distributed energy resources, which have become a new operation mode with substantial advantages such as high flexibility, adaptability, and economy. This paper proposes a distributionally robust optimal dispatch approach for virtual power plants to determine an optimal day-ahead dispatch under uncertainties of renewable energy sources. The proposed distributionally robust approach characterizes probability distributions of renewable power output by moments. In this regard, the faults of stochastic optimization and traditional robust optimization can be overcome. Firstly, a second-order cone-based ambiguity set that incorporates the first and second moments of renewable power output is constructed, and a day-ahead two-stage distributionally robust optimization model is proposed for virtual power plants participating in day-ahead electricity markets. Then, an effective solution method based on the affine policy and second-order cone duality theory is employed to reformulate the proposed model into a deterministic mixed-integer second-order cone programming problem, which improves the computational efficiency of the model. Finally, the numerical results demonstrate that the proposed method achieves a better balance between robustness and economy. They also validate that the dispatch strategy of virtual power plants can be adjusted to reduce costs according to the moment information of renewable power output.

Modeling energy consumption in the production processes of industrial units based on load response programs in the energy market

Baodong Li — Wed, 30 Nov 2022 00:00:00 +0800

The optimal operation of microgrids is of great significance for the sake of efficient and economic management of its energy resources. The microgrids energy management system should plan for operating the microgrid while considering the electric and thermal load simultaneously. The present study proposes energy management to minimize the costs of operating an industrial microgrid. In fact, planning for energy supply is among the critical issues that distribution companies deal with in the competitive environment every day. A distribution company usually meets customer (end customer) demands by purchasing energy from a wholesale market. Given the load curtailment, distribution companies have more choices and interactions in the market. Distribution companies face the two uncertainties of load changes and price fluctuations in their daily energy supply planning which could lead to the risk of loss resulting from the distribution company's decision-making for daily energy supply planning. Thus, these companies face the challenge of maximizing profit in a risk-based environment. Therefore, the present study presents an optimal model of energy consumption in the production processes of aluminum and cement industrial units. The presented model was then used in planning the day-ahead energy of a microgrid containing these industrial units. Since the studied subject has many limitations, it would be difficult to solve it using mathematical methods. To resolve this issue, the present study introduces a newly developed algorithm inspired by bee colonies. The proposed method seeks to make significant improvement in the local and global search capabilities. In addition to confirming the validity of the proposed model, results indicate that the implementation of load-response programs and the cooperation of industrial units in the ancillary services and energy market can increase the profits of units and microgrids as well as correcting the demand curve.

Implementing an optimal energy management system for a set of microgrids using the harmony search algorithm

Xiangjian Shi — Thu, 21 Jul 2022 00:00:00 +0800

A microgrid (MG) refers to a set of loads, generation resources and energy storage systems acting as a controllable load or a generator to supply power and heating to a local area. The MG-generated power management is a central topic for MG design and operation. The existence of dispersed generation (DG) resources has faced MG management with new issues. Depending on the level of exchanges between an MG and the main grid, the MG operation states can be divided into independent or grid-connected ones. Energy management in MGs aims to supply power at the lowest cost for optimal load response. This study examines MG energy management in two operational modes of islanded and grid-connected, and proposes a structure with two control layers (primary and secondary) for energy management. At the principal level of control, the energy management system is determined individually for all MG by taking into consideration the probability constraints and RES uncertainty by the Weibull PDF, generation resources’ power as well as the generation surplus and deficit of each MG. Then, the information of the power surplus and deficit of each MG must be sent to the central energy management system. To confirm the proposed structure, a case system with two MGs and a condensive load is simulated by using a multi-time harmony search algorithm. Several scenarios are applied to evaluate the performance of this algorithm. The findings clearly show the effectiveness of the proposed system in the energy management of several MGs, leading to the optimal performance of the resources per MG. Moreover, the proposed control scheme properly controls the MG and grid's performance in their interactions and offers a high level of robustness, stable behavior under different conditions and high quality of power supply.

Effects of Hydrogen Storage System and Renewable Energy Sources for Optimal Bidding Strategy in Electricity Market

Can Li — Thu, 21 Jul 2022 00:00:00 +0800

This work suggested a novel model for obtaining optimum bidding/offering strategy to improve the benefits in case of big users. Aiming this regard, several electrical energy resources including: micro turbines, green power sources (wind turbine and photovoltaic system), power storage unit such as Hydrogen storage system with fuel cell, as well as mutual treaties are taken into account in offered model. Considering various models for uncertain parameters based on their natures such as power demand, electricity market tariffs, solar irradiation, temperature and wind speed is one of the contributions of the proposed model. Uncertainty of power demand is modeled by robust optimal method whereas remain uncertain parameters are incorporated in model by stochastic method. Considering of wind speed cased is made by Weibull distribution. While, normal distribution is utilized for production of cases for electricity market tariffs, solar irradiation and temperature. In order to reduce the bidding error loss, the storage devices are corporate with green energy in power unbalanced conditions. Combined-integer linear programming method is applied for handling of pricing method profiles that have strength against considered uncertainties on power demand of big user. The obtained results confirm, the entire electrical energy supplement expenditure of big user in absence of demand uncertainty is $39,63 whereas it’s augmented up to $49,47 to achieve robustness versus demand uncertainty. Also, using of hydrogen storage system by considering the reliability index is reduced the bidding price of the system.

Optimal intelligent Reconfiguration of distribution network in the presence of distributed generation and Storage System

Gang Lei — Thu, 21 Jul 2022 00:00:00 +0800

In the present paper, the distribution feeder reconfiguration in the presence of distributed generation resources (DGR) and energy storage systems (ESS) is solved in the dynamic form. Since studies on the reconfiguration problem have ignored the grid security and reliability, the non-distributed energy index along with the energy loss and voltage stability indices has been assumed as the objective functions of the given problem. Besides, by adding the DGRs to the distribution grid, the radial mode of the grid and the one-sided passage of power are eliminated, and the ordinary and simple grid is replaced with a complex grid. In the present paper, the problem of distribution grid reconfiguration in the presence of DGR and ESS is solved by a developed particle swarm optimization (PSO) algorithm based on the self-adaptive operator. The proposed developed model has particularly improved the local and global search of this algorithm. The reconfiguration problem is discussed and investigated considering different scenarios in a standard 33-bus grid as a large-scale system in different scenarios in the presence and absence of the DGRs. Then, the obtained results are compared.

Optimal Intelligence Planning of wind power plants and power system storage devices in power station unit commitment based

Yuchen Hao, Yuchen Hao — Thu, 21 Jul 2022 00:00:00 +0800

Renewable energy sources (RES) such as wind turbines (WT) and solar cells have attracted the attention of power system operators and users alike, thanks to their lack of environmental pollution, independence of fossil fuels and very low marginal costs. With the introduction of RES, challenges have faced the solving of the unit commitment (UC) problem as a traditional power system optimization problem aiming to minimize total costs by optimally determining units’ inputs and outputs, and specifying the optimal generation of each unit. The output power of RES such as WT and solar cells depends on natural factors such as wind speed and solar irradiation that are riddled with uncertainty. As a result, the UC problem in the presence of RES faces uncertainties. The grid consumed load is not always equal to and is randomly different from the predicted values, which also contributes to uncertainty in solving the aforementioned problem. To overcome this problem, the current study proposes a novel two-stage optimization model with load and wind farm power generation uncertainties for the security-constrained UC problem. The new model is adopted to solve the wind-generated power uncertainty, and energy storage systems (ESSs) are included in the problem for further management. To solve the UC programming model, a hybrid honey bee mating and bacterial foraging algorithm is employed to reduce problem complexity and achieve optimal results.

Scavenging Effects of kaolin on Fine Ash Formation during Zhundong Coal Combustion

Dunxi Yu — Mon, 22 Mar 2021 00:00:00 +0800

The previous work found that the additive kaolin could scavenge not only sodium (Na) but also calcium (Ca) and magnesium (Mg), important ash fluxing agents in low rank coal combustion. Such scavenging effects of kaolin on fine ash formation were studied in the present work. A typical Zhundong coal and its blends with kaolin at dosages of 1, 2 and 4 wt% were combusted in an electrically heated drop tube furnace (DTF) at 1300 ℃. The fine ashes generated were collected and size segregated by a low pressure impactor (LPI). The morphology and chemical composition of fine ash were analyzed by scanning electron microscopy equipped with an energy-dispersive spectrometer (SEM-EDS). In addition, char/ash particles were sampled at various positions of DTF to elucidate how kaolin additive affected the fine ash formation process. The results further showed that apart from the scavenging of volatile Na, kaolin additive could also strongly scavenge the refractory Ca, Mg and Fe in the fine ash during Zhundong coal combustion, which transformed the sintered particles with irregular shape into melted spherical particles, and finally resulted in the considerable decrease of these elements in both PM_0.4 and PM_0.4-10 by melting and agglomeration. The close contacts between kaolin particles and coal resulted from physically mixing were a key factor responsible for the reaction of kaolin with the refractory Ca, Mg and Fe.

Emission Behaviors of Ultrafine Particles (PM1) Generated by the Combustion of Sesame Stalk after Combined Water Washing and Carbonization Pretreatment

Tianyu Liu — Mon, 22 Mar 2021 00:00:00 +0800

Pretreatment before biomass combustion is significant for its efficient utilization and that combined water washing and carbonization can be efficient. An agricultural processing residues sesame stalk was selected and carried out two pretreatments separately, i.e., water washing-torrefaction (W-T) and torrefaction-water washing (T-W), to explore the effect on the fuel properties, combustion characteristics and particulate matter (PM) emission. The obtained biochar was also combusted under air and oxy50 (CO₂:O₂=50:50) conditions for the sake of investigating the effect of pretreatment and combustion atmosphere. The results indicate that, W-T and T-W both not only have great effect on the improvement of fuel properties but also reduce the content of water-soluble elements like K, Cl, et al. Due to the difference in hydrophobicity, the biochar obtained by W-T have the optimal fuel properties. At the same time, the pretreatment also hinder the combustion in a certain extent in which the comprehensive combustion characteristics (S_N) show a downward trend. Furthermore, both two pretreatments have obvious benefit on the reduction of PM₁ emission and W-T have the best effect related to the higher removal efficiency of inorganic elements (especially K+Na+Cl+S). Under oxy50 condition, the oxygen concentration and combustion temperature is higher, improving the sulfation of K and vaporization of Ca, P and Mg which result in weakening in the pretreatment reduction effect on PM₁ emission.

Uncertainties in the mercury mass balance in a coal-based IGCC power plant (Puertollano, Spain)

Wed, 02 Jun 2021 00:00:00 +0800

Mercury (Hg) is a global pollutant that is subject to strict regulations to reduce anthropogenic emissions. The production of energy represents an important activity that leads to Hg emissions into the atmosphere. Of all the systems used, IGCC plants are the most promising for reducing Hg emissions, since it is possible to remove the Hg from syngas prior to combustion. The aim of the present work was to evaluate the presence of Hg in the main streams of an experimental IGCC plant (ELCOGAS, Puertollano) to quantify Hg emissions and investigate the possibility of reducing them. The main streams of the system were sampled for three consecutive days and both the solids, i.e., raw material (coal and petroleum coke), fine and coarse slags, fly ash, sulphur, and the liquids, i.e., slag system, venturi scrubber and saturator, were studied. The results show that an average of 12.90% of the Hg that enters the IGCC power plant is eliminated with solid waste and only 0.08% with liquid waste. There is still an average of 87.12% of Hg that is not accounted for in the mass balance and this could remain in the system and/or be eliminated in the streams that were not analysed. Although it is impossible to offer an explanation for the final fate of the Hg lost in the system based on the data obtained, the data do suggest that sulphur by-products could be primarily responsible for the elimination of Hg from the syngas, and that a major proportion of Hg should be emitted via the chimney after the syngas combustion process.

Impacts of Torrefaction on PM10 emissions from Biomass Combustion

Zihao Wang, Dunxi Yu, Jingkun Han, Jianqun Wu — Sat, 17 Jul 2021 00:00:00 +0800

Torrefaction is considered to be a competitive technology for biomass pretreatment, but its impacts on the emission of particulate matter from biomass combustion is worth of further study. In this paper, three waste biomasses, i.e., bagasse, wheat straw and sawdust were selected for torrefaction pretreatment and the impacts of torrefaction on the emission characteristics of PM₁₀ from biomass combustion were investigated. The combustion experiments were carried out on a drop tube furnace. The combustion-generated particulate and bulk ash samples were collected and subjected to analyses by various techniques. The results show that torrefaction tends to result in a reduction of PM₁(particulates with an aerodynamic diameter less than 1μm) emissions from combustion, but the extent of reduction is dependent on biomass type. This phenomenon is mainly because that the torrefaction process removes some Cl and S from the biomass, thereby suppressing the release of alkali metals and the emission of PM₁ during the combustion process. As for PM_1-10 (particulates with an aerodynamic diameter within 1-10μm), its emissions from combustion of torrefied biomasses are consistently reduced, compared with their untreated counterparts. This observation is primarily accounted for by the enhanced particle coalescence/agglomeration in combustion of torrefied biomasses, which reduces the emission of PM_1-10.

Experimental Research on Mercury Catalytic Oxidation over Ce modified SCR catalyst

Yadi Qin — Sat, 04 Dec 2021 00:00:00 +0800

In order to improve the ability of SCR catalyst to catalyze the oxidation of gaseous elemental mercury, a series of novel Ce modified SCR(V₂O₅–WO₃/TiO₂) catalysts were prepared via two-step ultrasonic impregnation method.The performance of Ce/SCR catalysts on Hg⁰ oxidation and NO reduction as well as the catalytic mechanism on Hg⁰ oxidation was also studied.The X-ray diffraction (XRD), Brunauer Emmet Teller (BET) measurements and X-ray photoelectron spectroscopy (XPS) were used to characterize the catalysts. The results showed that the pore volume and pore size of catalyst was reduced by Ce doping, and the specific surface area decreased with the increase of Ce content in catalyst.The performance on Hg⁰ oxidation was promoted by the introduction of CeO₂.Ce₁/SCR (1%Ce,wt.%)catalyst exhibited the best Hg⁰ oxidation activity of 21.2% higher than that of SCR catalyst at 350◦C,of which the NO conversion efficiency was also higher at 200-400℃.

Furthermore,the addition of CeO₂ improved the ability to resist H₂O.HCl was the most effective gas responsible for the Hg⁰ oxidation.The chemisorbed oxygen and weak absorbed oxygen on the surface of catalyst were increased by the addition of CeO₂.The redox cycle (V⁴⁺ + Ce⁴⁺ ↔ V⁵⁺ + Ce³⁺) played an important role in promoting Hg⁰ oxidation.

Emission Characteristics of Particulate Matter and SOx in Wet Flue Gas Desulfurization and Wet Electrostatic Precipitator

Xu Zhao, Houzhang Tan, Fuxin Yang, Shuanghui Deng — Sat, 04 Dec 2021 00:00:00 +0800

In order to reduce the environmental smog caused by coal combustion, air pollution control devices have been widely used in coal-fired power plants, especially of wet flue gas desulfurization (WFGD) and wet electrostatic precipitator (WESP). In this work, particulate matter with aerodynamic diameter less than 10 μm (PM₁₀) and sulfur oxides (SO_x) have been studied in a 660 MW coal-fired power plant. The plant is equipped with selective catalytic reduction, electrostatic precipitator, WFGD, WESP. The results show that the PM₁₀removal efficiencies in WFGD and WESP are 54.34% and 50.39% respectively, and the overall removal efficiency is 77.35%. WFGD and WESP have effects on the particle size distribution. After WFGD, the peak of particles shifts from 1.62 μm to 0.95 μm, and the mass concentration of fine particles with aerodynamic diameter less than 0.61 μm increases. After WESP, the peak of particle size shifts from 0.95 μm to 1.61 μm. The differences are due to the agglomeration and growth of small particles. The SO₃ mass concentration increases after SCR, but WFGD has a great influence on SO_x with the efficiency of 96.56%. WESP can removal SO_x, but the efficiency is 20.91%. The final emission factors of SO₂, SO₃, PM₁, PM_2.5 and PM₁₀ are 0.1597, 0.0450, 0.0154, 0.0267 and 0.0215 (kg·t^-1), respectively. Compared with the research results without ultra-low emission retrofit, the emission factors are reduced by 1~2 orders of magnitude, and the emission control level of air pollutants is greatly improved.

HCl-Induced Hg0 Transformation over CuMn2O4 Sorbent

Aijia Zhang, Yingju Yang, Jing Liu, Junyan Ding — Mon, 24 Jan 2022 00:00:00 +0800

CuMn₂O₄ spinel has been regarded as a highly efficient sorbent for Hg⁰ capture from flue gas. The regenerability and recyclability of CuMn₂O₄ sorbent are mainly associated with the mercury speciation adsorbed on its surface. However, the effect mechanism of HCl on Hg⁰ transformation over CuMn₂O₄ sorbent is still elusive. Experiments were conducted to understand the effect of HCl on Hg⁰ transformation over CuMn₂O₄ sorbent. The results indicate that CuMn₂O₄ sorbent is a mesoporous material and possesses a good thermal stability. CuMn₂O₄ shows >95% Hg⁰ removal efficiency in a wide temperature window of 50-350 ºC. The favorable electron-transfer environment caused by the mixed valence states of Cu and Mn cations is responsible for the excellent Hg⁰ removal performance of CuMn₂O₄ sorbent. CuMn₂O₄ shows a higher Hg⁰ adsorption capacity of 4774.57 μg/g. Hg⁰ adsorption process over CuMn₂O₄ sorbent can be well described by the developed kinetic model. Hg⁰ removal efficiency of CuMn₂O₄ sorbent does not depend on the presence of HCl. Mercury species adsorbed on the CuMn₂O₄ sorbent in the presence of HCl mainly exist in the forms of HgO and HgCl₂O₈•H₂O. HCl shows a significant effect on mercury speciation over CuMn₂O₄ sorbent. Most of HgO species will be transformed into HgCl₂O₈•H₂O in the presence of HCl.

Angle Scattering Method for Soot Concentration Measurement under Ultra-low Emissions Condition

Bin Yang, Xingchen Zhu, Jie Deng, Xiaoxu Guo, Jinke Han, Xiaowei Liu — Mon, 24 Jan 2022 00:00:00 +0800

Aiming at the problem of soot concentration measurement under ultra-low emission conditions, a forward small angle soot concentration measurement method is proposed. Taking a typical boiler emission of 0.1μm-3.0μm bimodal distribution soot as an object, the particle scatter simulation calculation under different parameters is carried out, and the influence of detection angle and particle size on the angular scattering measurement of ultra-low emission soot is analyzed. The influence of detection angle and particle size on the angular scattering measurement of ultra-low emission soot is analyzed. Preferably, the wavelength of incident light is 650nm, and the forward detection angle parameter is 15° for the design of forward small angle soot concentration measurement system. An experimental system for measuring smoke and dust with standard concentration is built, and experimental research on particle concentration measurement of 1.0μm and 3.0μm under ultra-low emission conditions are carried out. The results show that the average deviation of soot concentration measurement in once experiment is less than 0.10 mg/m³ under the condition of ultra-low emission by using 15° of forward detection, which provides an effective way for monitoring ultra-low emission soot concentration in coal-fired power plants.

Multi-agent Consensus Control Scheme for the Load Control Problem

Te Xu, Zhixian Lin, Xinwei Lin, Changsheng Lin, Feng Gao, Zixuan Li, Peiwen Liu — Mon, 23 May 2022 00:00:00 +0800

With the help of smart grid technologies, a lot of electrical loads can provide demand response to support the active power balance of the grid. Compared with centralized control methods, decentralized methods reduce the computational burden of the control center and enhances the reliability of the communication. In this paper, a novel second-order multi-agent consensus control method is proposed for load control problem. By introducing the velocity state into the model, the proposed method achieves better performance than traditional ones. Simulation results verifies the effectiveness of the proposed method.

Kalman-Filtering-based Frequency Control Strategy Consider-ing Electrolytic Aluminum Load

Yuqin Chen, Shihai Yang, Yueping Kong, Mingming Chen; Yuqing Bao — Mon, 23 May 2022 00:00:00 +0800

Kalman-Filtering-based Frequency Control Strategy Consider-ing Electrolytic Aluminum Load

A Novel Aquila Optimizer based PV Array Reconfiguration Scheme to Generate Maximum Energy under Partial Shading Condition

Dong An, Junqing Jia, Wenchao Cai, Deyu Yang, Chao Lv, Jiawei Zhu — Mon, 23 May 2022 00:00:00 +0800

This paper develops a real-time PV arrays maximum power harvesting scheme under partial shading condition (PSC) by reconfiguring PV arrays using Aquila optimizer (AO). AO is based on the natural behaviors of Aquila in capturing prey. It can choose the best hunting mechanism ingeniously and quickly by balancing the local exploitation and global exploration within four hunting methods of Aquila: choosing the searching area through high soar with the vertical stoop, exploring in different searching spaces through contour flight with quick glide attack, exploiting in convergence searching space through low flight with slow attack, and swooping through walk and grab prey. In general, reconfiguring PV arrays is a problem of discrete optimization, thus a series of discrete operations are adopted in AO to enhance its optimization performance on PV arrays reconfiguration. Simulation results based on 10 cases under PSCs show that the mismatched power loss obtained by AO is the smallest compared with genetic algorithm, particle swarm optimization, and butterfly optimization algorithm.

Sustainability Evaluation of Modern Photovoltaic Agriculture Based on Interval Type-2 Fuzzy AHP-TOPSIS and Least Squares Support Vector Machine Optimized by Fireworks Algorithm

Yi Liang, Haichao Wang, Wei-Chiang Hong — Sat, 04 Dec 2021 00:00:00 +0800

Timely and accurate sustainability evaluation of modern photovoltaic agriculture is of great significance for accelerating the sustainable development of modern photovoltaic agriculture. In order to improve the timeliness and accuracy of evaluation, this paper proposes an evaluation model based on Interval Type-2 Fuzzy AHP-TOPSIS and least squares support vector machine optimized by fireworks algorithm. Firstly, the criteria system of modern photovoltaic agriculture sustainability is constructed from three dimensions including technology sustainability, economic sustainability and social sustainability. Then, analytic hierarchy process (AHP) and technique for order preference by similarity to an ideal solution (TOPSIS) methods are improved by using interval type-2 fuzzy theory, and the traditional evaluation model based on interval type-2 Fuzzy AHP-TOPSIS is obtained, and the improved model is used for comprehensive evaluation. After that, the optimal parameters of least squares support vector machine (LSSVM) model are obtained by Fireworks algorithm (FWA) training, and the intelligent evaluation model for the sustainability of modern photovoltaic agriculture is constructed to realize fast and intelligent calculation. Finally, an empirical analysis is conducted to demonstrate the scientificity and accuracy of the proposed model. This study is conducive to the comprehensive evaluation of the sustainability of modern photovoltaic agriculture, and can provide decision-making support for more reasonable development model in the future of modern photovoltaic agriculture.

Sustainability Intelligent Evaluation of Regional Microgrid Interconnection System Based on Combination Entropy Weight Rank Order-TOPSIS and NILA-KELM

Haichao Wang, Yingying Fan — Fri, 01 Apr 2022 00:00:00 +0800

Sustainability evaluation of regional microgrid interconnection system is conducive to a profound and comprehensive understanding of the impact of interconnection system projects. In order to realize the comprehensive and scientific intelligent evaluation of the system, this paper proposes an evaluation model based on combination entropy weight rank order-TOPSIS and Niche Immune Lion Algorithm -Extreme Learning Machine with Kernel (NILA-KELM). Firstly, the sustainability evaluation indicator system of the regional microgrid interconnection system is constructed from four aspects of economic, environmental, social, and technical characteristics, and the evaluation indicators are explained. Then, the classical evaluation model based on TOPSIS is constructed, and the entropy weight method and rank order method (RO) are coupled to obtain the indicator weight. The niche immune algorithm is used to improve the lion algorithm, and the improved lion algorithm is used to optimize the parameters of KELM, and the intelligent evaluation model based on NILA-KELM is obtained to realize fast real-time calculation. Finally, the scientificity and accuracy of the model proposed in this paper are verified analysis. This study is conducive to the horizontal comparison of the overall performance of regional microgrid interconnection system projects, helps investors to choose the most promising project scheme, and helps the government to find feasible project.

Performance Analysis of a Rooftop Hybrid Connected Solar PV System

Hasan Falih, Ahmed J. Hamad, Abdul Hadi N. Khalifa — Mon, 23 May 2022 00:00:00 +0800

In the present work, a 5-kW hybrid PV solar system was installed on the roof of a house in Diyala, Iraq (33.77° N, 45.14° E elevation 44 m). The system consists of two strings where each string consists of nine polycrystalline PV modules with 355 Wp in series and the two strings are in parallel. The energy storage system (ESS) consists of two parallel strings, each with four 12 V and 150 Ah tubular deep cycle batteries in series. A hybrid inverter of 5 kW rated power was operated in different modes. The results showed that the monthly energy production for May was about 822.9 kWh, while the monthly energy consumption was 1085 kWh. The percentage distribution of the DC energy produced was about 1% system energy losses, 27.9% was used to charge the ESS, 34.3% was used to feed to the grid and the remaining 37.64 % was used to share the load. The energy percentage shearing the load was 16.67% from ESS, 33.33% from the PV system and 50% purchased. The average daily reference, array, and final yields were 6.07, 4.327, and 3.991 h/day, respectively. The average array and load efficiencies were 12.3 and 92.24% with the performance ratio at 65.4%.

Deep Learning Network for Energy Storage Scheduling in Power Market Environment Short-Term Load Forecasting Model

Yunlei Zhang, Ruifeng Cao, Sha Peng, Danhuang Dong, Ruoyun Du, Xiaomin Xu — Thu, 21 Jul 2022 00:00:00 +0800

In the electricity market, fluctuations of real-time prices are unstable, and changes in short-term load are determined by many factors. By studying the timing of charging and discharging and the economic benefits of energy storage in the process of participating in the power market, this paper takes energy storage scheduling as one factor affecting short-term power load, which affects short-term load time series with time-of-use price, holidays, and temperature. A deep learning network is used to predict the short-term load, a convolutional neural network (CNN) is used to extract the features, and a long short-term memory (LSTM) network is used to learn the temporal characteristics of the load value, which can effectively improve the prediction accuracy. Taking the load data of a certain region as an example, the CNN-LSTM prediction model is compared with the single LSTM prediction model. The experimental results show that the CNN-LSTM deep learning network with the participation of energy storage in dispatching can have high prediction accuracy for short-term power load forecasting.

Analysis of Solar Direct-driven Organic Rankine Cycle Powered Vapor Compression Cooling System Combined with Electric Motor for Official Building Air-conditioning

Xiang Xiao, Wei Zhao, Wei Wang, Wei Zhang, Xianbiao Bu, Lingbao Wang, Huashan Li — Wed, 18 Nov 2020 00:00:00 +0800

Solar energy powered organic Rankine cycle/vapor compression cycle (ORC/VCC) is a good alternative to converting solar heat into a cooling effect. However, solar heat is an unstable and discontinuous energy, which needs the back-up source or heat storage equipment to ensure smooth operation, thus resulting in a higher engineering expense. To resolve this problem, a hybrid cooling system driven by solar energy combined with electric motor is proposed in this study. An official building located in Guangzhou and opened from 9:00 am to 5:00 pm is selected as the study subject, and the research results through thermodynamic analysis show that (1) direct radiation intensity and generation temperature have important effects on the system performance. There is always an optimal generation temperature at which the system performance can achieve the maximum values. The key indicator of cooling power per square meter collector should be especially considered while designing a hybrid cooling system; (2) due to having the electric motor, solar driven ORC/VCC cooling system can operate stably even solar energy is unstable and discontinuous, and the electric motor will start when the cooling capacity provided by solar energy cannot meet the requirement of the whole building cooling load. Compared to the vapor compression cooling system, the hybrid cooling system can save almost 65.46% of electricity consumption.

Field investigation and comparison analysis of low-grade heat pump technologies in building space heating projects

Yanxue Li — Sat, 04 Dec 2021 00:00:00 +0800

A large share of final energy consumption is allocated to the building sector, improving building energy efficiency expected to play a significant role in mitigating social carbon dioxide emission. Herein, we collected the on-site measurement data to investigate the techno-economic performances of existing different heat pump types under real-world building space heating projects in Qingdao, China. Statistical analysis revealed the temperature variations of low-grade heat sources over the whole heating supply period, urban sewage water features with high quality and stable heat energy supply compared with seawater and geothermal heat resources. Operational behaviors including cycling inlet and outlet temperature of the selected heat pumps were illustrated, analysis evaluated detailed effects of operational parameters on energy efficiency performances. Then the relationship between COPs distributions of heat pumps and operational conditions was examined further, positive effect of the rising temperature of heat sources on energy efficiency performance of heat pump is highlighted when the heating supply temperature is higher. Furthermore, the economic feasibility sensitive analysis considering the NPV performances of heat pump systems was carried out. Finally, we recommended potential suggestions for improving the overall energy efficiency and cost competitiveness of decentralized heat pumps for building space heating.

Numerical Study on Heat Transfer Characteristic of The Plate-fin Microchannel Heat Sink for Water-based Thermal Management of CPU Chip

Jiechao Chen, Nan-Long Hong, Rui-Hao Luo, Wu-Zhi Yuan, Wen-Hao Wang — Mon, 23 May 2022 00:00:00 +0800

For effective water-based thermal management of high heat generating CPU chip, a series of numerical simulation has been conducted to study the effects of heat flux, fin height and flow rate on convective thermal performance of the plate-fin microchannel heat sinks. The characteristics of heat transfer and flow resistance have been quantificationally discussed and JF factor is employed to evaluate the comprehensive efficiency of convective heat transfer of microchannel heat sink. Results show that the increase in fin height and flow rate of cooling water is helpful to decrease the maximum temperature of CPU chip. Large flow rate and heat flux and short fin height are benefit to improve Nusselt number Nu, but they lead to large resistance coefficient fRe simultaneously. Analysis of JF factor shows that the microchannel with short fins shows better convective thermal performance when the thermal power of the CPU chip is small. The fins should be heightened when the CPU is operating at higher thermal power. The employment of JF factor in the present work shows its pertinence and convenience in the application of design of microchannel heat sink.

A Novel Power Curve Prediction Method for Horizontal-Axis Wind Turbines Using Artificial Neural Networks

Yong Chai Tan — Mon, 22 Mar 2021 00:00:00 +0800

Accurate prediction of wind turbine power curve is essential for wind farm planning as it influences the expected power production. Existing methods require detailed wind turbine geometry for performance evaluation, which most of the time unattainable and impractical in early stage of wind farm planning. While significant amount of work has been done on fitting of wind turbine power curve using parametric and non-parametric models, little to no attention has been paid for power curve modelling that relates the wind turbine design information. This paper presents a novel method that employs artificial neural network to learn the underlying relationships between 6 turbine design parameters and its power curve. A total of 198 existing pitch-controlled horizontal-axis wind turbines have been used for model training and validation. The results showed that the method is reliable and reasonably accurate, with average R² score of 0.9966.

Long-Term Electricity Demand Forecasting for Malaysia Using Artificial Neural Networks in The Presence of Input and Model Uncertainties

Yong Chai Tan — Tue, 23 Mar 2021 00:00:00 +0800

Electricity demand is also known as load in electric power system. This article presents a Long-Term Load Forecasting (LTLF) approach for Malaysia. An Artificial Neural Network (ANN) of 5-layer Multi-Layered Perceptron (MLP) structure has been designed and tested for this purpose. Uncertainties of input variables and ANN model are introduced to obtain the prediction for years 2022 to 2030. Pearson correlation is used to examine the input variables for model construction. The analysis indicates that Primary Energy Supply (PES), population, Gross Domestic Product (GDP) and temperature are strongly correlated. The forecast results by the proposed method (henceforth referred to as UQ-SNN) are compared with the results obtained by a conventional Seasonal Auto-Regressive Integrated Moving Average (SARIMA) model. The R² scores for UQ-SNN and SARIMA are 0.9994 and 0.9787, respectively, indicating that UQ-SNN is more accurate in capturing the non-linearity and the underlying relationships between the input and output variables. The proposed method can be easily extended to include other input variables to increase the model complexity and is suitable for LTLF. With the available input data, UQ-SNN predicts Malaysia will consume 207.22 TWh of electricity, with standard deviation (SD) of 6.10 TWh by 2030.

Reliability Based Multi-Objective Thermodynamic Cycle Optimisation of Turbofan Engines Using Luus-Jaakola Algorithm

Yong Chai Tan — Wed, 02 Jun 2021 00:00:00 +0800

Aircraft engine design is a complicated process, as it involves huge number of components. The design process begins with parametric cycle analysis. It is crucial to determine the optimum values of the cycle parameters that would give a robust design in the early phase of engine development, to shorten the design cycle for cost saving and man-hour reduction. To obtain a robust solution, optimisation program is often being executed more than once, especially in Reliability Based Design Optimisations (RBDO) with Monte-Carlo Simulation (MCS) scheme for complex systems which require thousands to millions of optimisation loops to be executed. This paper presents a fast heuristic technique to optimise the thermodynamic cycle of two-spool separated flow turbofan engines based on energy and probability of failure criteria based on Luus-Jaakola algorithm (LJ). A computer program called Turbo Jet Engine Optimiser v2.0 (TJEO-2.0) has been developed to perform the optimisation calculation. The program is made up of inner and outer loops, where LJ is used in the outer loop to determine the design variables while parametric cycle analysis of the engine is done in the inner loop to determine the engine performance. Latin-Hypercube-Sampling (LHS) technique is used to sample the design and model variations for uncertainty analysis. The results show that optimisation without reliability criteria may lead to high probability of failure of more than 40% on average. The proposed algorithm is able to solve the turbofan RBDO problem within 3 minutes.

Electricity Demand Time Series Forecasting Based on Empirical Mode Decomposition and Long Short-term Memory

Behnam Talebjedi, Timo Laukkanen, Timo Laukkanen, saman taheri — Fri, 17 Sep 2021 00:00:00 +0800

Load forecasting is critical for a variety of applications in modern energy systems. Nonetheless, forecasting is a difficult task because electricity load profiles are tied with uncertain, non-linear, and non-stationary signals. To address these issues, long short-term memory (LSTM), a machine learning algorithm capable of learning temporal dependencies, has been extensively integrated into load forecasting in recent years. To further increase the effectiveness of using LSTM for demand forecasting, this paper proposes a hybrid prediction model that incorporates LSTM with empirical mode decomposition (EMD). EMD algorithm breaks down a load time-series data into several sub-series called intrinsic mode functions (IMFs). For each of the derived IMFs, a different LSTM model is trained. Finally, the outputs of all the individual LSTM learners are fed to a meta-learner to provide an aggregated output for the energy demand prediction. The suggested methodology is applied to the California ISO dataset to demonstrate its applicability. Additionally, we compare the output of the proposed algorithm to a single LSTM and two state-of-the-art data-driven models, specifically XGBoost, and logistic regression (LR). The proposed hybrid model outperforms single LSTM, LR, and XGBoost by, 35.19%, 54%, and 49.25% for short-term, and 36.3%, 34.04%, 32% for long-term prediction in mean absolute percentage error, respectively.

Classification of transmission line ground short circuit fault based on convolutional neural network

Ao Zhimin — Fri, 01 Apr 2022 00:00:00 +0800

Ground short circuit faults in current transmission lines are one of the most common faults in power systems. In order to prevent the power system from aggravating the accident caused by short-circuit faults of transmission lines, a novel convolutional neural network (CNN) model is constructed to identify the short-circuit fault of the transmission line in the power system. This method uses a fixed time window to intercept system short-circuit fault data, and extracted the deep features of these data from the training samples, and then corresponded the extracted features to labels one-to-one. Finally, in PSCAD/EMTDC, the new England 10 machine 39 nodes are taken as an example to realize the simulation. The experimental results show that the CNN model could quickly and accurately identify the short-circuit fault type, and the optimal model accuracy rate reached 99.95%. The results of this manuscript were of positive effect on enhancing the disaster prevention capability and the operation stability of transmission lines.

Research on the Flow and Heat Transfer Characteristics of a Water-Cooling Board in a Heat Dissipation System

Yu kun Lv, Zhuang Wei, Fan Yang, Shuang Yang — Sat, 18 Sep 2021 00:00:00 +0800

The water-cooling heat dissipation technology can solve the heat dissipation and noise problems of the calculation board. Among them, the structural design of the water-cooling board directly affects its flow and heat transfer characteristics, which restricts the promotion and application of the technology. To this end, the water-cooling board of a heat dissipation system is taken as the research object, and its flow and heat transfer characteristics are numerically simulated and experimentally studied. Through comparative analysis, the rationality of the numerical simulation method is verified. On this basis, three water-cooling board structure improvement schemes are drawn up and numerically simulated, and the selected optimal program is experimentally verified. The results of the study show that, compared with the original water-cooling board, the optimized water-cooling board has increased internal flow velocity and even distribution, increased heat transfer by 4.2%, and the average temperature of the Calculation board decreased by 5.3%.

Advancements in the Development of Various Types of Dye-Sensitized Solar Cells (DSSC): A Comparative Review

Wed, 02 Jun 2021 00:00:00 +0800

The global increase in energy demand has resulted in the depletion of non-renewable resources and caused environmental degradation. Consequently, emerging renewable technologies are a potential solution to fulfil energy demand and mitigate the effect of global warming. Low-cost solar energy harvesting technologies are most feasible technologies. Various solar cells technologies have been developed with improved overall performance and conversion efficiency. However, due to low cost and a wide range of applications, dye-sensitized solar cells (DSSCs) have been immensely focused on one of the most promising third-generation solar cells. The highest conversion efficiency of DSSC achieved after three decades of research is more than 14%, but the commercialization of this technology is still a challenge. In this review paper, an attempt has been made to present the comparison of different articles published, that gives the in-depth study of recent developments in various types of DSSCs based on architectural assembly and physical appearance. An overview of the limitations and challenges with their possible improvement strategies have also been discussed. This review paper concludes that appropriate selection of electrolytes dramatically affects the performance of DSSC, and quasi-solid state electrolyte proves to be a better option. Besides, it also concludes that tandem structures are widely agreed with the approach to expand light utilization spectrum for an overall increase in its performance. However, still, the research is required, which could efficiently widen the applications of the DSSCs.

Review on Wind Power Development and Relevant Policies Between China and Japan

Zekun Wang — Fri, 17 Sep 2021 00:00:00 +0800

In developing countries, China has the most abundant wind energy resources and huge development and utilization potential. Japan is a developed country which is currently plans to increase the use of renewable energy, especially wind energy. This research is aimed at reviewing on the development of wind power and relevant policies between China and Japan. Firstly, introduced the current status of global wind power development, such as global installed capacity of wind power. And then the annual development of wind power generation in China and Japan is compared and the distribution characteristics of wind resources are compared. Furthermore, market share in China and Japan are introduced. Finally, according to comparing the difference of government policies between the China and Japan, the existing problems in the wind power industry are pointed out, and give some suggestions for the development of wind turbine for China and Japan. These suggestions should be taken into account when designing national climate policies and have an important reference value for the future development of China's wind energy industry.

A Review of Research Status and Scientific Problems of Floating Offshore Wind Turbines

Xinbao Wang — Sat, 04 Dec 2021 00:00:00 +0800

随着海上风力资源的不断利用，海上风力发电机的安装深度和容量不断增加。为了满足可再生能源的建设要求并成为公众关注的焦点，风力发电技术和风电场必将进一步发展到海洋中。结果，随着时代的要求，出现了一种新型的风力发电设备，即浮式海上风力发电机（FOWT）。因此，本文对一些关键科学难题的研究提供了客观的评论。首先，讨论了有关国际海上风能市场需求和装机容量的统计和预测。之后，总结了在国外建设FOWT和浮动风力发电项目的优势。进而，本文描述了模型涡轮机的比例缩放设计，湍流和尾流的流动特性，浮动平台在六自由度下的运动响应，负载波动控制技术以及其他一些重大科学问题的研究现状。无论是理论分析，数值模拟，海洋工程盆地测试，风洞实验还是原型海域测量，FOWT都有望突破各种障碍，最终实现高效，稳定的商业运营。

Development of Transient Electric Field Radiation Simulation Device During Gas Insulation Switch Operation

Hao YANG — Sat, 04 Dec 2021 00:00:00 +0800

In gas insulation switch (GIS) substation, secondary devices such as line monitoring devices are placed in the switching field, and these electronic devices are vulnerable to transient electromagnetic interference caused by switching operation. In order to facilitate the measurement and research of electromagnetic disturbance data under different working conditions, a simulation test device is developed in this paper, which can be used to simulate electromagnetic disturbance of GIS substation sensor and secondary device port under switch operation. A four-channel parallel gas switch was designed, and the main characteristic parameters of electromagnetic disturbance generated by the simulation device were measured by using high-frequency pulse power supply as the excitation source. The comparison between the measured waveform and the measured disturbance characteristic parameters of GIS substation shows that it is in good agreement with the measured waveform characteristics, conforms to the basic characteristics of damped oscillation wave, and can be used in the secondary equipment port disturbance voltage coupling characteristics, protection measures evaluation and assessment method research.

Performance Evaluation of Small-channel Pulsating Heat Pipe Based on Dimensional Analysis and ANN Model

Xuehui Wang, Edward Wright, Zeyu Liu, Neng Gao, Ying Li — Mon, 24 Jan 2022 00:00:00 +0800

The pulsating heat pipe is a very promising heat dissipation device to address the challenge of higher heat-flux electronic chips as it is characterised by excellent heat transfer ability and flexibility for miniaturisation. To boost the application of PHP, reliable heat transfer performance evaluation models are significantly important. In this paper, a heat transfer correlation was firstly proposed for closed PHP with various working fluids based on collected experimental data. Dimensional analysis was used to group the parameters. It was shown that the average absolute deviation (AAD) and correlation coefficient (r) of the correlation were 40.67 % and 0.7556, respectively. For 95% of the data, the prediction of thermal resistance and the temperature difference between evaporation and condensation section fell within 1.13 K/W and 40.76 K, respectively. Meanwhile, an artificial neural network model was also proposed. The ANN model showed a better prediction accuracy with a mean square error (MSE) and correlation coefficient (r) of 7.88e-7 and 0.9821, respectively.

Modeling and Optimal Design of a PV/ Fuel Cell (SOFC) Hybrid Power System for a Mediterranean City

Sat, 18 Sep 2021 00:00:00 +0800

This work presents a hybrid power system consisting of photovoltaic and solid oxide fuel (PV-SOFC) for electricity production and hydrogen production. The simulation of this hybrid is adjusted for Bou-Zedjar city in Algeria. The method used depends on the annual average monthly values of radiation for which the energy contributions are determined for each component. The economic study is a more important criterion in the proposed hybrid system, and the results show that the cost is very suitable for the use of this hybrid system, which ensures that the area is fed continuously with the sufficient energy. The optimized results of the present study show that the PV is capable of production 8733 kW while the SOFC produces 500 kW. The electrolyzer is capable of producing 238750 kg of hydrogen which is used as fuel in the SOFC.

Research on Intelligent Control Strategy of Hybrid Energy Storage System with Ethernet Communication

Lu Wang — Fri, 16 Oct 2020 00:00:00 +0800

Abstract: The increasingly severe global energy crisis has brought great challenges to the energy field, and renewable energy power generation system has been widely concerned because of its characteristics of green and inexhaustible. However, renewable energy also has some limitations in its specific application, and affects the grid-connected power generation of new energy. In this paper, based on the background of photovoltaic power station, it firstly proposed the control strategy of using hybrid energy storage system to assist a single inverter in photovoltaic power station to resist low voltage ride-through, and the DC component of fluctuating power during low voltage ride-through is extracted by using the moving average function, furthermore, the control strategy of bidirectional DC/DC converters both the lead-acid battery side and the super capacitor side is proposed to ensure the stability of DC bus voltage. Then, by using the Ethernet communication technology of the computer, the energy of the hybrid energy storage system of the power station is allocated reasonably to maintain the energy of the battery in a reasonable range. Finally, the system verification and experimental analysis show that the proposed intelligent control strategy can effectively achieve the control requirements of hybrid energy storage system, and the simulation and experimental results can also verify the feasibility and effectiveness of the proposed method.

A Review of Spill of LNG on Concrete Ground

Shier Dong — Wed, 18 Nov 2020 00:00:00 +0800

Abstract：Based on the analysis of the whole process of LNG spill on land, the research methods of LNG pool expansion and heavy gas diffusion are summarized and analyzed. This paper reviews the experimental and analytical work performed to data on spill of LNG. Specifically, experiments on the spill of LNG onshore, as well as experiments and numerical study on heavy gas dispersion. Pool boiling and turbulence model are described and discussed, as well as models used to predict dispersion and thermal hazard. Although there have been significant progress in understanding the behavior of LNG spills, technical knowledge gaps to improve hazard prediction are still identified. Some of the gaps can be addressed with current modeling and testing capabilities. Finally, a discussion of the state of knowledge, and recommendations to further improvement the understanding of the behavior of LNG spills onshore.

Research on Green Energy Development System under the Background of Environmental Sustainability

Ruliang Zhang — Wed, 18 Nov 2020 00:00:00 +0800

Abstract: As an important means to promote the energy revolution, the emergence of the energy internet system provides a new opportunity for the marketization, liberalization and flexibility of multi-energy transactions. Firstly, based on the core concept of the energy internet system, the preliminary definition and construction goals of the energy internet system market are proposed, and the specificity of the energy internet system market is obtained by comparing with the traditional energy, natural gas, regional heating/cooling and other single energy markets. It is mainly reflected in the four aspects of supporting comprehensive transactions of multiple types of energy, achieving market participation of large-scale distributed entities, supporting flexible and intelligent energy consumption and increasing dependence on information technology. Secondly, the system design and transaction mechanism of the energy internet system market are analyzed and discussed in detail. Finally, it summarizes the key issues and research prospects in the development process of the energy internet system market.

Experimental Research of the Radiator Thermal Performance Test Equipment and its Application in Energy System

Lian Zhang — Fri, 25 Dec 2020 00:00:00 +0800

Abstract: Radiator thermal performance test equipment play a key role in the processing of develop a new type of heat radiator and its application products. For a radiator thermal performance test equipment, the precise of temperature controlling, temperature measuring and flow measuring are the vital factors. Based on above background, this paper improves the system as well as the precise and veracity of the control and measure system of this core problem in radiator thermal performance test equipment. This paper also optimizes the software and hardware system simultaneously so as to improve the precision of the auto-test system of test equipment. The flow rate is range from 175 kg/h to 178 kg/h under different conditions. The average is 176.5 kg/h and the deviation rates are from 1.62% to 1.97%. The heating is different from each other: the maximum is 4.3 kW and the minimum is 4.2 kW in condition 1; the maximum is 3.3 kW and the minimum is 3.2 kW in condition 2; the maximum is 1.95 kW and the minimum is 1.89 kW in condition 3. But the deviation rate is about 2.9%. Thus, this test equipment has high steady and good accuracy. This paper studies a new electronic heat cost allocate meter test method by radiator thermal performance test equipment too. In the test of electronic heat cost allocate meter, this paper test temperature changes in four measures points and get a result appeared as a heat backup which must avoid when using. From this test and research, some experiences and references could be gained for further research and enhance the characteristic of new products of heating system.

Cloud based monitoring and diagnosis of gas turbine generator based on unsupervised learning

Xian Ma — Tue, 23 Mar 2021 00:00:00 +0800

Abstract: The large number of gas turbines in large power companies is difficult to manage. A large amount of data from generating units is not mined and utilized for fault analysis. This study focuses on F-class 300MW gas turbine generators, and uses unsupervised learning and cloud computing technologies to analyze the faults of large gas turbines. Remote monitoring and diagnosis of operational status. The study proposes a cloud computing service architecture for large gas turbine objects. The unsupervised learning model to realize the monitoring gas turbine operation.

A Simplified Model for SO2 Generation during Spontaneous Combustion of Coal Gangue

Ang Li — Sat, 17 Jul 2021 00:00:00 +0800

Abstract: A simplified model for SO₂ emission during spontaneous combustion of coal gangue hill was put forward and the calculated SO₂concentration agrees reasonably with the measured data. Using this model, the effects of initial temperature inside the gangue and the fresh air supply were discussed. The results show that higher initial temperature inside the gangue can accelerate the oxidation rate of FeS₂ and increase the maximum concentration of SO₂. Besides, the increase of maximum concentration of SO₂ grows more quickly than the increase of temperature. Fresh air supply has little effect on the oxidation rate of FeS₂. But more fresh air supply could oxidize more FeS₂, which means more SO₂ can be generated. Though there exist some relatively large errors between computational results and measured data regarding inner locations inside the gangue, this model can provide a relatively precise SO₂ release at an acceptable extent, which can also provide a useful method to predict hazardous material generation and total pollutant release, such as CO, NOx, and chlorine during spontaneous combustion of coal gangue hill.

Establishment of a Coupling Model for the Prediction of Heat Dissipation of the Internal Combustion Engine Based on Finite Element

Yinyan Wang — Fri, 01 Apr 2022 00:00:00 +0800

Abstract: The paper focuses on the performance of traditional automobile internal combustion engines, using fractional difference algorithm to analyze the coupling relationship of thermal boundary conditions among various models of internal combustion engine heated parts temperature, and conducts finite element analysis based on the test data of existing internal combustion engines to obtain the enhanced internal combustion engine the heat dissipation of the whole machine. According to the test results, the calculation and prediction of the heat dissipation of the whole machine and the adjustment of various non-coupling calculation boundary conditions are carried out. Based on this, the performance of the newly designed internal combustion engine and the boundary conditions are calculated to extrapolate and predict the distribution of heat dissipation of the whole machine.

Suitability Evaluation of Hydrogen Production and Hydrogenation Station based on AHP - Fuzzy Comprehensive Evaluation Method

Sainan Zhang — Mon, 23 May 2022 00:00:00 +0800

As for the fact that there are multiple influencing factors and lack of evaluation standards for the construction of in-station hydrogen production and hydrogenation station, this paper constructs the suitability evaluation system of hydrogenation station from four aspects of technology, economy, environment and safety. Combined with the actual situation, this paper uses analytic hierarchy process (AHP) and fuzzy comprehensive evaluation model to evaluate the suitability of hydrogen production from electrolytic water and hydrogen production from natural gas reforming. In the analysis of the index weight ranking, the results show that the gas leakage rate (0.281), hydrogen purity (0.144), and the flammability and explosibility of raw materials (0.143) rank the top three, indicating that safety is the most important indicator and must be highly regarded. In addition, the maximum value of the hydrogen production result from the electrolysis of water and the hydrogen production from natural gas reforming is 0.682 and 0.552 respectively, which both correspond to "Excellent". Thus, the results show that two ways of hydrogen production methods have good comprehensive benefits. However, the technology of hydrogen production from electrolytic water should be preferentially selected, because on the whole, the technology of hydrogen production from electrolytic water has better benefits than that from natural gas reforming. In the future, it is suggested that renewable energy should be vigorously developed to generate hydrogen, and at the same time, the economic and environmental benefits of hydrogen production from electrolytic water can be improved.

Energy Efficient Thermal Comfort Control for Residential Building Based on nonlinear EMPC

Bing Kong — Thu, 21 Jul 2022 00:00:00 +0800

For purpose of achieving the desired thermal comfort level and reducing the economic cost of maintaining the thermal comfort of green residential building, an energy efficient thermal comfort control strategy based on economic model predictive control (EMPC) for green residential buildings which adopts household heat metering is presented. Firstly, the nonlinear thermal comfort model of heating room is analyzed and obtained. A practical nonlinear thermal comfort prediction model is obtained by using an approximation method. The economic cost function and optimization problem of energy-saving under the necessary thermal comfort requirements are constructed to realize the optimal economic performance of the dynamic process. The energy efficient thermal comfort MPC(EETCMPC) is designed. Finally, the comparison and analysis between EETCMPC and the two-layer economic performance optimization MPC strategy (DMPC) is simulated. The simulation results reveal that the radiant heat of radiator is reduced by 8.9% when adopting EETCMPC, and the economic performance is improved in the thermal comfort dynamic process of heating room.

Latent Heat Prediction of Nano Enhanced Phase Change Material by ANN Method

Farzad jaliliantabar, Rizalman Bin Mamat, Sudhakar Kumarasamy — Fri, 01 Apr 2022 00:00:00 +0800

Thermal characteristics of phase change material (PCM) are important in design and utilization of thermal energy storage or other applications. PCMs have great latent heat but suffer from low thermal conductivity. Then, in recent years, nano particles have been added to PCM to improve their thermophysical properties such as thermal conductivity. Effect of this nano particles on thermophysical properties of PCM has been a question and many experimental and numerical studies have been done to investigate it. Artificial intelligence-based approach can be a good candidate to predict thermophysical properties of nano enhance PCM (NEPCM). Then, in this study an artificial neural network (ANN) has been developed to predict the latent heat of the NEPCM. A comprehensive literature search was conducted to acquire thermal characteristics data from various NEPCM to train and test this artificial neural network model. Twenty different types of Nano particle and paraffin based PCMs were used in ANN development. The most important properties which are used as the input for the developed ANN model are NP size, density of NP, latent heat of PCM, density of PCM, concentration and latent heat of NEPCM in the range of 1-60 nm, 100-8960 kg/m3, 89.69-311 kJ/kg, 760 to 1520 kg/m3, 0.02-20 wt% and 60.72-338.6 kJ/kg, respectively. The output variable was latent heat of NEPCM. The result indicates that the ANN model can be applied to predict the latent heat of nano enhanced PCM satisfactory. The correlation coefficient of the created model was 0.97. This result shows ability of ANN to predict the latent heat of NEPCM.

An Updated Review on Low-temperature Nanocomposites with a Special focus on Thermal Management in Buildings

Mon, 23 May 2022 00:00:00 +0800

Buildings contribute to 33% of total global energy consumption, which corresponds to 38% of greenhouse gas emissions. Enhancing building’s energy efficiency remains predominant in mitigating global warming. Advancements in thermal energy storage (TES) techniques using phase change material (PCM) have gained much attention among researchers, primarily to minimize energy consumption and to promote the use of renewable energy sources. PCM technology stays asthe most promising technology for the developing high-performance and energy-efficient buildings. The major drawback of PCM is its poor thermal conductivity which limits its potential use. This could be outrun by dispersing conductive nanofillers. which can be overcome by technologies. The acquired database on synthesis routes, properties, and performance of NePCMs with various techniques presented in the paper should deliver useful information in the production of NePCMs with desirable characteristics mainly for building construction applications. An outline of contemporary developments and use of nano-enhanced phase change materials (NePCMs) as TES medium is deiverd. Finally, a brief discussion on challenges and the future outlook was also made. In-depth research is needed to explore the fundamental mechanisms behind the enhanced thermal conductivity of NePCM with nanofillers dispersion and to investigate how these mechanisms drive improvement in building performance.

A Preliminary Assessment of Load Consumption and Solar Power Potential at Eco-Tourism Centre Of Liogu Ku Silou-Silou, Kota Belud, Sabah

Mon, 23 May 2022 00:00:00 +0800

For sustainable electrical energy development in a specific area of Kinabalu Geopark (Sabah), a project to implement an off-grid solar PV system was initiated. In this paper, a detailed preliminary assessment of load consumption and solar power potential data which carried out at Eco-Tourism centre of Liogu Ku Silou-Silou or simply EPLISSI, Kota Belud, Sabah are presented. The motivation behind this preliminary assessment is due to the nonexistence of electrical grid and power supply to this area. Basically, this area is a blackout area, causing the operation of EPLISSI as a recreational area is limited to daytime. Therefore, data from this preliminary assessment are crucial in effort to develop an off-grid solar photovoltaic (PV) system design. With power supply, EPLISSI’s visitors will be able to extend their stay. This also means an extra profit for EPLISSI in the long run. On the other hand, load consumption data is important in the development process of a solar PV system design. Hence, an excel based software named ESCoBox will be used to assist in the production of load profiles. The input data for this software are coming from the list of future electrical appliances and based on the visitor logbook (frequency of visitors). Meanwhile, to assess the solar power potential at EPLISSI, an online simulator known as Global Solar Atlas version 2.3 or GSA 2.3 are used. As a result, it is found that the site requires a total average demand as well as a total peak demand of 4.60 kWh/day and 11.87 kWh/day, respectively. From the GSA 2.3 generated report, an off-grid solar PV system of capacity 2.50 kWp solar PV can satisfy the daily total average load demand of this area, where the average PV energy output is within the range of between 7.74-9.80 kWh/day or an average of 8.72 kWh/day. In conclusion, the outcome from this preliminary assessment indicates that the installation of an off-grid solar PV system in this area is possible.

BIOCHEMICAL ANALYSIS OF SPIRULINA BIOMASS THROUGH FTIR, TGA, CHN

RUMA ARORA SONI — Wed, 02 Jun 2021 00:00:00 +0800

Spirulina is a sort of algae that develops in both fresh and seawater. It is considered the Earth's most nutritionally-dense food. In the present investigation, Fourier transforms infrared spectroscopy,thermogravimetric analysis technology, the elemental analysis was used to study spirulina biomass biochemical characteristics. The optimal content of spirulina protein, lipid, and amino acid was identified and reported. During the study period, the various frequency ranges corresponding to functional groups are evaluated and reported. Spirulina FT-IR spectra were recorded and reported at different frequency ranges from 3870-3448 cm^-1 to 695-545 cm^-1. FTIR studies forspirulina biomass affirmed the occurrence of –OH, –COOH, NH, C-H, and C= O groups. Results indicate that Spirulina sp biomass is viable green energy and the biggest protein source. Protein (3453 and 1645 cm^-1) and carbohydrate (1032 and 1033 cm^-1) were the main components with distinct IR spectra fingerprint characteristics.

Improved Thermophysical properties of Developed Ternary Nitrate-based Phase Change Material Incorporated with MXene as Novel Nanocomposites

kumaran kadirgama — Sat, 17 Jul 2021 00:00:00 +0800

In this study, nanocomposite of ternary nitrate molten salt induced with MXene is developed. LiNO3-
NaNO3-KNO3 with wt % of 35:12:53 and 35:10:55 are produced and doped with MXene in the wt.%
of 0.2, 0.5, 1.0, and 1.5. FTIR result indicates the composites had no chemical reaction occurred
during the preparation. UVVIS shows the absorption increases with the concentration of Mxene.
Thermogravimetric analysis (TGA) was used to measure the thermal stability of the LiNO3-NaNO3-
KNO3 induced with MXene. The ternary molten salts were stable at temperature range of 600-700°C.
Thermal stability increases with the addition of Mxene. 1.5 wt.% of MXene doped with LiNO3-NaNO3-
KNO3 with wt% 35:10:55 and 35:12:53, increases the thermal stability from 652.13℃ to 731.49℃
and from 679.82℃ to 684.57℃ respectively. Using thermophysically enhanced molten salt will
increase the efficiency of CSP.

Statistical Model for Impact and Energy Absorption of 3D Printed Coconut Wood-PLA

Sat, 17 Jul 2021 00:00:00 +0800

This study attempts to provide a statistical evaluation regarding the effect of infill pattern and percentage towards energy absorption and impact energy of the coconut wood-filled PLA filaments printed through 3D printing technique. The developed model is based on the acquired experimental data accompanied by response surface methodology. Besides determining significant parameters, this analysis also provides modeling of impact properties and optimization of the parameter for desired properties performance. Based on the analysis, it is identified that the investigated factors such as infill pattern, infill percentage, the second-order term of infill pattern, the second-order term of infill percentage, and the interaction effect of infill pattern and infill percentage show a significant impact on the energy absorption. According to ANOVA analysis, the value of R² is equal to 96.59%, indicates the model fits the data better. The S value equal to 0.0311246 suggests that the models' lower S value predicts the response better. Meanwhile, adjusted R² equal to 94.69% is responsible for the number of predictors in the model that describes the relationship's importance. This response optimization helps identify the preferable value of the printing parameters used in the given constraint to produce the highest energy absorption capacity. Based on the performed analysis, it is shown that the maximum energy absorbed could achieve is 0.824 J, and it can be achieved with a parameter combination of honeycomb pattern and 75% infill percentage.

Techno-Economic Analysis of a Grid Connected Waste to Energy Gasification Plant to power a Community.

Ahmed Elwan, Mohammed Haffiz Habibuddin — Fri, 17 Sep 2021 00:00:00 +0800

: Municipal solid waste management and demand for energy are the two competing challenges globally. This can be attributed to population growth and change in life style. Tackling these requires an approach for an optimal waste management system that offers added value to the population with less environmental impact. This work evaluates the techno-economic and environmental analysis of a grid connected waste to energy (WtE) plant to supply electricity to a small community. Energy recovery potential of the waste stream was evaluated using LCA methodology in Gabi software. Subsequently, technical, economic and environmental analysis was conducted for the WtE grid connected plant using HomerPro software using gasification WtE plant. Cash flow analysis was based on levelized energy cost, total net present value (NPV). From the results, an NPV for the system is $1.11x107 most impact coming from grid operational cost with a levelized cost of energy at 0.43$/kWh against the grid unit price of 0.7$/kWh this translates into a savings of 0.27$/kWh in the purchase of energy. From an environmental angle, results showed significant decrease in emissions of carbon dioxide from approximately 2,000 tons per year to about 400 tons per year. In terms of the amount of waste sent to the landfills the results show a significant improvement from 142,605.5 kg/year to 0.13kg/year.

Effect of Flow Field Geometry on Hydrodynamics of Flow in Redox Flow Battery

Sat, 04 Dec 2021 00:00:00 +0800

This study computationally investigates the hydrodynamics of different serpentine flow field designs for redox flow batteries, which considers the Poiseuille flow in the flow channel and the Darcy flow porous substrate. Computational Fluid Dynamics (CFD) results of the conventional serpentine flow field (CSFF) agreed well with those obtained via experiment, thus proving the present CFD analysis's validity on the modified variation of serpentine flow fields. The results indicate significant improvement in the porous substrate's wet-ability and decreased pressure drop across the channel for modified versions of CSFF designs which are very important for the cell's electrochemistry performance.

Effect of thermal conductivity of tube-wall on blow-off limit of a micro-jet methane diffusion flame

Bing Liu, Yikun Chen, Huachen Liu, Qiao Wu, Minghui Wang, Jianlong Wan — Mon, 24 Jan 2022 00:00:00 +0800

The operating range of the flow rate or flow velocity for the micro-jet flame is quite wide, which can be used as the heat source. In order to optimize the micro-jet tube combustor in terms of the solid material, the present paper numerically investigates the impact of thermal conductivity (λ_s) on the operating limit of micro-jet flame. Unexpectedly, the non-monotonic blow-off limits with the increase of λ_s is found, and the corresponding generation mechanisms are analyzed in terms of the thermal coupling effect, flow field, and strain effect. At first, the lower preheating temperature of the fuel and larger heat loss amount to the environment lead to a larger blow-off limit at a larger λ_s. After that, the smaller local flow velocity in the vicinity of flame root and smaller strain effect slightly increase the blow-off limit with the continuously increasing λ_s. Therefore, it is deduced that the applied performance of micro-jet combustor with a smaller thermal conductivity is better in terms of the blow-off limit.

Energy and life cycle assessment of Zinc/water nanofluid based Photovoltaic Thermal system

Syed Mohd Yahya — Mon, 24 Jan 2022 00:00:00 +0800

Cooling the PV surface in a Photovoltaic Thermal system is a pivotal operational aspect to be taken into account to achieve optimized values of performance parameters in a Photovoltaic Thermal System. The experimental design used in this study facilitates the flow of varying concentrations of Zn-water nanofluid in serpentine copper tubing installed at the rear of the PV panel thereby preventing the PV surface temperature from increasing beyond the threshold value at which a decrease in electrical efficiency starts to occur. This fusion of solar thermal with PV devices leads to better electrical and thermal efficiency values resulting in decreased cell degradation over time and maximization of the lifespan of the PV module and the energy output from the PV system. Due to the superior thermal heat properties of nanofluids, their usage in such systems has become increasingly widespread. Life Cycle metrics which include Energy Payback period, Energy Production Factor and life cycle conversion efficiency were evaluated for the PVT system by exhaustively chalking fundamental parameters such as embodied energy of the PVT setup and the total energy output from the PVT system. This research aims to be a major milestone in the evolutionary journey of Photovoltaic Thermal modules by guiding the engineers working on the theory, design and implementation of PVT systems towards its economic feasibility, environmental impact and energy sustainability.

Effect of Varying Temperature and Oxygen on Particulate Matter Formation in Oxy-Biomass Combustion

Fri, 01 Apr 2022 00:00:00 +0800

Experimental results are reported on the emission quantity and observed profile of particulate matter (PM) formation during oxy-biomass combustion. The laboratory setup included a fixed bed electric reactor and a particulate matter (PM) measuring machine interfaced with the flue gas from the fixed bed reactor combustion chamber. Readings of the PM concentration were taken every second in mg/m3. The experiments were conducted at seven different temperatures (600°C-1200°C) and six incremental oxygen concentrations (21%-100%). Five biomass types were studied; A-cornstalk, B-wood, C-wheat straw, D-Rice husk, E-Peanut shell, each pulverized to a size of approximately 75 microns. There was a substantial level of congruency in the observed profile of PM emission from the five biomass fuels investigated. Significantly high PM formation was observed from the herbaceous, fibrous biomass with low density. Peak PM formation points amounting to 57% occurred at oxygen levels between 21% and 30%, 43% occurred at oxygen levels of 50% and above. Ash pulverization during char combustion was identified as the key pathway to PM formation in oxy-fuel combustion. It was also observed that increase in temperature leads to a reducing decrease in time of combustion.

Experimental performance analysis of a Corrugation Type Solar Air Heater (CTSAH)

Aravindh M A, Aarjab Ghimire, Sreekumar A — Mon, 23 May 2022 00:00:00 +0800

This paper explains the performance evaluation of a Corrugated Type Solar Air Heater

(CTSAH) is analysed experimentally. Experiments were conducted at different mass flow

rates and its effect on the heat gain, efficiency, friction factor heat transfer etc. were analysed.

Simulation is carried out for different mass flow rates i.e. M1=0.06, M2=0.14, M3=0.17,

M4=0.25, M5=0.3 and is conducted from 1100 hrs. to 1400 hrs. The air inlet air temperature

is found to be in an average of 40°C whereas the incident solar radiation is in the average of

795 W/m2 . Simulation result shows that the outlet temperature increases with the increase in

incident solar radiation and inlet air temperature and decreases with the increase in inlet air

velocities. Experimental results show that the optimum performance of the CTSAH is in the

mass flow rate range of 0.14-0.25. Also, the calculated useful heat produced, convective heat

transfer coefficients, effective efficiency, optical efficiency provides knowledge on the

potential use of the air heater.

Hierarchical and Distributed Optimal Control Strategy for Power and Power Quality of Microgrid Based on Finite-time Consistency

Wenjun Wei, hao Liang — Thu, 21 Jul 2022 00:00:00 +0800

Droop control is one of the main control strategies of islanded microgrid (MG), but it cannot realize the rational power distribution of distributed power supply of MG and will cause frequency and electrical pressure deviation from the rating, and the power quality is poor. To solve this problem, a hierarchical distributed power and power quality optimization strategy based on multi-agent finite-time consistency algorithm (MA-FTC) is proposed in this paper. Firstly, based on droop control, the frequency voltage compensation is introduced by using the FTC to stabilize the frequency and voltage of the system at the rated value. Secondly, the MAS-FTC is used to calculate the total active power and reactive power reserve capacity of the system, so that when the load side of the system changes, each DG can achieve reasonable and accurate distribution of active power and reactive power according to its proportion in the total standby capacity. Finally, a 4-node MG system was established by MATLAB/Simulink, which verified the correctness and effectiveness of the proposed optimization strategy, and the convergence time was shortened by nearly 60%.

Investigating the Effects of the Driving Cycle and Penetration of Electric Vehicles on Technical and Environmental Characteristics of the Hybrid Energy System Considering Uncertainties

Mojtaba Ghadamyari — Thu, 21 Jul 2022 00:00:00 +0800

Electric vehicles (EVs) have been received special considerations from modern society over the past years. Although EVs are a fine example of environmentally friendly technology and have many advantages, they increase the electricity demand of a power grid. Therefore, their negative impact on buses’ voltage and line losses should be analyzed. In this study, the impact of the urban driving cycle and penetration of EV’s on buses voltage and line losses of an IEEE-33 buses system has been examined. At the second step of research, the above-mentioned IEEE-33 buses system include renewable resources such as photovoltaic panel and wind turbine. Moreover, the effect of EVs on the rate of air pollution which are produced by fossil fuel electricity generators has been investigated. It is important to say that the positive effects of demand response as an appropriate way to deal with EV loads have been discussed in this research. Generally, the simulation of this paper provides a novel and wider perspective on EVs.

Design of Nonlinear Uncertainty Controller for Grid-Tied Solar Photovoltaic System using Sliding Mode Control

Menaga D, PREMKUMAR M, Sowmya R, Narasimman S — Fri, 16 Oct 2020 00:00:00 +0800

The proposed controller accompanies different sliding surfaces to understand maximum power point
extraction as opposed to nonlinear uncertainties and unknown disturbance of grid connected photovoltaic
system with two control inputs (ud; uq) to extract maximum power from a solar array and maintain unity
power flow in a grid by controlling voltage across dc link capacitor (Vpvdc) and reactive current (iq).
A innovative controller verifies uncertain inputs, constant and changes in irradiance and temperature
of the photovoltaic system. The performance characteristics have been compared to two sliding mode
controllers and validated through numerical simulation.

A Novel DC-DC Converter Topology for Renewable Energy Systems

Fri, 25 Dec 2020 00:00:00 +0800

Renewable energy can be utilized for the generation of electrical power with sources such as photovoltaic (PV) or fuel cell. But these sources generate fewer voltage values and therefore require high gain converters to match with DC bus voltage in microgrids. These high gain converters can be implemented with switched capacitors to meet the required of DC bus voltage. Switched capacitors operate in a series and parallel combination during switching operation produces high static gain and limits reverse voltage that appears across the components. A novel converter is proposed that satisfies all the features such as high voltage gain, only one switch, forces less potential stress cross the components, ripple current is less. These features of the proposed converter are verified through MATLAB/SIMULINK.

Investigation of inverter temperature prediction model in wind farm based on SCADA data

Qihui Ling, Wei Zhang, Qiancheng Zhao, Juchuan Dai — Sat, 04 Dec 2021 00:00:00 +0800

The inverter is one of the key components of the wind turbine, and it is a complex circuit composed of a series of components such as a variety of electronic components and power devices. Therefore, it is very difficult to accurately identify the operating status of the inverter and some problems of its own circuit, especially in the early stage of its failure. However, considering whether the inverter heats up normally from the perspective of heat dissipation, it provides a way for the early state identification of the inverter. If the inverter temperature prediction model can be established, the early state can be identified through the judgment of the output temperature. Based on this starting point, this paper analyzes some factors that affect the temperature of the inverter, and determines the input and output parameters of the prediction model. Then, using the neural network method, the inverter multi-input multi-output temperature prediction model is established. Finally, through case analysis, it is found that the established temperature model can indeed be used to identify early temperature anomalies. The construction method of the prediction model can be used for reference to other aspects of wind turbines. All these brings huge benefits to wind energy industry.

Bearing fault diagnosis method of wind turbine based on improved anti-noise residual shrinkage network

Li Xiao lei — Mon, 24 Jan 2022 00:00:00 +0800

A new bearing fault identification method based on the Improved Anti-noise Residual Shrinkage Network (IADRSN) is proposed for the difficulties of rolling bearing fault diagnosis in wind turbines in noisy environments. Firstly, the vibration signals of wind turbine rolling bearings were preprocessed to obtain data samples divided into training and test sets. Then, a bearing fault diagnosis model based on the improved anti-noise residual shrinkage network was established. To improve the ability of fault feature extraction of the model, the convolution layer in the deep residual shrinkage network was replaced with a DenseNet layer. To further improve the anti-noise ability of the model, the first layer of the model was set as the Dropblock layer. Finally, the labeled training set data samples were input into the model for training, and the trained model was applied to the test set to output the fault diagnosis results. The results showed that the proposed method could achieve the fault diagnosis of wind turbine bearing more accurately in the high noise environment through comparison and verification.

Multi-objective reactive power optimization for large-scale access of electric kiln to distribution network

wu dan — Sat, 17 Jul 2021 00:00:00 +0800

With the great progress of the "coal to electricity" project, the electric kiln equipment began to be connected to the distribution network on a large scale, which caused the problems of low voltage and high reactive power quality. This paper presents a multi-objective reactive power optimization algorithm for power distribution network after electric kiln is connected in scale. Firstly, a multi-objective optimization model is established to minimize the active network loss, voltage deviation and equipment cost under the constraint conditions of voltage margin, power factor and reactive power compensation capacity. Secondly, the weighted method is used to transform the multi-objective optimization model into the single-objective optimization model, and Matlab and OpenDSS software are used for joint simulation, and particle swarm optimization is used to determine the optimal installation location and capacity of the reactive power compensation device. Finally, taking IEEE33 distribution network as the object and considering the change of electric furnace permeability in the range of 20%-50%, the simulation results show that the proposed algorithm is effective, which can effectively reduce the loss of distribution network and significantly improve the voltage of distribution network.

Influencing Factors of Total Factor Energy Efficiency in Bohai Rim Region Based on DEA-Tobit Model

Weifeng Gong, Xiaohong Qi, Chuanhui Wang — Mon, 23 May 2022 00:00:00 +0800

Bohai Rim region is an important economic development area and a large carbon emission area in China. It is of great significance to explore the total factor energy efficiency and its influencing factors for the low carbon transformation and high-quality development of the Bohai Rim region. Based on the total factor energy efficiency framework, the DDF-DEA model was used to calculate the total factor energy efficiency, and the internal and external differences of the total factor energy efficiency were further analyzed. The internal and external influencing factors were determined by ML index method and classical endogenous growth theory, and then the Tobit panel model was used to empirically analyze the action mechanism of all influencing factors of total factor energy efficiency in the Bohai Rim region. The results show that the pure technical efficiency, scale efficiency and technological progress among the internal influencing factors contribute to the improvement of energy efficiency in the Bohai Rim region. Industrial structure, industrial internal structure and ownership structure inhibit the improvement of energy efficiency. Energy consumption structure and energy endowment also have a negative impact on energy efficiency. Therefore, measures such as promoting technological progress, adjusting economic structure and optimizing energy structure will effectively improve total factor energy efficiency in the Bohai Rim region.