In this paper, the thermal performance of an all SiC 650 V, 116 A MOSFET power module has been studied by numerical simulation. Aiming at the heat dissipation problem of the SiC power devices in the inverter, three integrated liquid cooling heat sinks with different channel structures were designed. Results showed that compared with the other two cooling structures, the serpentine flow channel cooling structure can provide the best cooling effect. For the serpentine flow channel cooling structure, the heat source maximum temperature increases as the fin thickness increases, and the pressure drop decreases as the fin thickness increase when the coolant flow rate is constant. The improved heat sink has been numerical tested up to 110 A showing the device maximum temperature of 39.8Â°C, which can well meet the design requirements.
Natural gas has been recognized as a promising resource for urban energy system due to the less air pollution and a reliable supply transported along pipelines. A simplified physical model is established in this paper, which simulates the direct correlation of compressor operations and the inlet flux at each station to be the theoretical foundation of pipeline control. The deep neural network is designed then, with the corresponding input features and output results connected via certain hidden layers representing the complex hydraulic processes occurred along the pipeline. After training and network tuning using practical operation data, the trained model is shown to be effective in predicting the inlet flux at certain station as a consequence of certain operations on the compressors, which is essentially needed for the controllers in an urban energy controlling center.
In this work the possibility of a triple generation system for a seasonal pumped thermal energy storage (PTES) is investigated. Residential cooling via a heat pump (HP) is used to load a simple seasonal thermal storage during the summer season and unload it when the requirement of residential heating occurs. While unloading the high temperate, heat is used to power an Organic Rankine Cycle (ORC), whose low temperature condensation heat is then used to heat the building. Therefore, power and heat is stored in the summer and used during the winter. This combines the usage of increased renewable power generation during the summer, especially from photovoltaic and the reduction of fossil or power intensive heating requirements during the winter. Power to power efficiencies of up to 29.2 % with latent and 25.4 % with sensible storages were achieved.
With the rapid development of urbanization and motorization, the number of automobiles in China’s cities has increased dramatically, which has caused a series of problems such as urban road traffic congestion, increased energy consumption and urban air pollution, which have become more and more serious and become hot issues of concern to the entire society. Urban residents, as the main body of low-carbon travel, play a vital role in energy conservation and emission reduction of urban transportation. This paper reviews the existing research results and draws on a large and growing body of literature to propose the extension theory of planned behavior, to study the influencing factors of low-carbon travel choices of residents in China’s four first-tier cities. The study employs distribution of 3,000 network questionnaires and the collection of micro-survey data, to interpret urban residents from the traveler’s personal attributes, travel attributes, environmental attitudes, subjective norms, behavioral attitudes, behavioral control and other aspects of the traveler’s personal attributes. At the same time, it will also provide practitioners with practical and feasible policy recommendations.
The nonuniform reaction inside the fuel cell seriously affects the performance and durability of the fuel cell. Segmented cell is a method of measuring the internal electrochemical reaction. A segment method which is easy to process is to groove on the terminal of the electrode plate. In order to study the influence of the grooving method on the segmented fuel cell, three-dimension, five serpent channels, single-phase fuel cell models with and without grooves on the anode plate are established in this paper. Under steady state, the polarization curve of the cell and the current density distribution of the anode terminal are compared. Under dynamic state, how the current density of the nine segments of the segmented cell changes with the cathode stoichiometric ratio is studied. The final conclusion has important guiding significance for the judgment of the internal reaction uniformity of the segmented fuel cell by grooving method and provide a theoretical basis for judging whether a fuel cell is out of oxygen by segmented fuel cell.
This paper focuses on the major driving forces of the inequality in renewable energy technology innovation. We employ Gini coefficient and Shapley decomposition with semi-log regression model to examine the inequality in renewable energy technology innovation and contribution level of major driving factors in China during 2008-2017. The results show that the Gini coefficient of technology innovation with ultimately around 0.53 is obviously imbalanced in China, yet the unequal distribution display a decrease trend. The factors including R
Increasing municipal wastes poses a great threat to public health and further worsening environmental pollution. Urban garbage has become one of the main sources of environmental pollution in Chinese cities, and Urban Garbage Classification (UGC) has become the best option for China. The key to effective implementation of garbage classification lies in the willingness and behavior of residents. We investigate the deviation between willingness to garbage classification (WTC) and behavior of garbage classification (BGC) of residents to the UGC. This study is based on a random survey conducted in China’s cities. We find that firstly more willingness to garbage classification do not mean a higher chance of BGC, which indicates a deviation exists between the WTC and the BGC. Second, such a deviation depends mainly on contextual factors and residentsâ€™ attitudes and knowledge about the UGC. Third, respondents who live in a community with more supporting facilities for the UGC or know more about the UGC, are more likely to participate in garbage classification. Hence, the government should increase the supporting facilities for the UGC and related services to provide a convenient environment for residents to participate in the UGC. Furthermore, strengthening the popularization of knowledge about the UGC to the public can effectively minimize the deviation. This study provides a new perspective for research on alleviating environmental pollution and improving the quality of public health.
The Carbon fiber electrode is a cathode material in all-vanadium flow battery. In order to further reduce the volume of the all-vanadium power storage system, further reduce the internal resistance of the carbon fiber electrode, increase the current density of the electrode, and achieve high electrical conductivity and large electrostatic capacitance are essential. Among them, the graphitization of the positive electrode material and the improvement of the specific surface area of the electrode surface also greatly affect the performance of the all-vanadium redox flow battery. Therefore, in this paper, carbon nanotubes (CNTs) with small diameter and large specific surface area are thermal plated on the surface of conventional carbon fibers, and the specific resistance can be reduced to almost half by increasing the specific surface area of the carbon fibers. The charge and discharge experiments of the all-vanadium flow battery prove that this method is very effective to improve the performance of the all-vanadium flow battery.
Energy consumption of Chinaâ€™s mining industry is larger than the total energy consumption of some European countries, such as the Netherlands and Spain. It is therefore significant to study the driving forces of the mining industryâ€™s energy and carbon performance. This paper adopts the non-radial directional distance function to calculate the energy and carbon performance of Chinaâ€™s mining industry and uses metafrontier Malmquist index to disassemble the results into three components to analyze the driving forces of the mining industryâ€™s energy and carbon performance improvement during the 11th and 12th five-year plan. We found that the main forces that drive the energy and carbon performance improvement are catch-up effects and technical gap ratio change, but the innovation effect does not have obvious contribution to the improvement. As for policymakers, the government should support improving the technology progress of the mining sector, reduce surplus capacity, and open up the mineral market.
In order to study the effect of different configurations of photovoltaic thermal system on its performance, this paper analyzes the energy and exergy of photovoltaic thermal system with different coolant and heat exchanger configurations with numerical simulation methods. Basically, the heat transfer process between the PV panel and coolant in two different configurations, i.e., the straight tube and the wave tube. Furthermore, the temperature, energy and exergy efficiencies of the two configurations based on pure water cooling photovoltaic thermal system are compared. The results show that the wave tube has the best performance with the maximum thermal efficiency of 58.38% and the electrical efficiency of 11.41%, which are 4.37% and 3.56% higher than the straight tube respectively. In addition, the corresponding exergy efficiency is increased by 4% at the same condition. A lower concentration of CNT/water nanofluid has better performance in practical applications. When the volume concentration is 0.15%, the photovoltaic thermal system has a maximum thermal efficiency of 57.99%, and an electrical efficiency of 11.39%, the exergy efficiency is 11.95%. It is very important to configure the structure of the photovoltaic thermal system and select the appropriate nanofluid.