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The DC distribution system is an important development direction of the distribution system, which can improve the reliability and the quality of the power supply, and support the new energy, the energy storage, the electric vehicles, and the flexible access of AC and DC loads to grid. To realize the demonstration application of the DC distribution technology, China’s first demonstration project of the medium voltage DC distribution network will be built in Zhuhai, Guangdong Province to support the construction of the city energy internet. First, this paper analyzes the demand of the DC distribution network project, and puts forward the construction content and construction target. Then, it designs and analyzes the electrical connection mode, system operation mode, and startup and shutdown mode of the DC distribution network, and proposes the overall project construction plan. Finally, it conducts the specific project design and analysis, which mainly include the selection of equipment such as inverters, DC transformers and DC circuit breakers, the design and analysis of the DC control and protection system, the design and analysis of the over-voltage protection and the configuration scheme of the lightning arrester, and analysis of the system transient characteristics. The design and analysis of the engineering program is a combination of China’s distribution network engineering practice and technical characteristics, which lays a solid foundation for the advancement of the DC power distribution technology in China, and has reference value and demonstration effect for the design and construction of other projects.

Abstract The automotive operating protocols is a comprehensive expression of a country or a region’s road, climatic environment and driving habits. It is the foundation of energy consumption, test method and limit method for automobile products. It has direct impact on R & D, production and government access management of enterprises. For fuel cells vehicles, the lifetime is one of the main factors restricting their commercialization. Furthermore, the lifetime evaluation methods and its standard specifications of vehicular proton exchange membrane fuel cell are the critical factors to its technological development, but there is no authoritative recognized life evaluation method and test protocols so far. A logical fuel cell durability test protocol is the fundamental for developing the fuel cell life evaluation methods. A review on the state-of-art in the world for fuel cell accelerated test protocols was given, the research circumstances of different universities and research institutions in China, America, the European Union, Japan and so on are analyzed and summarized in detail. Then the essential characteristics and applicable environments of a comprehensive and effective durability test protocol are summarized based on the analysis and demonstration of the existing durability test protocols in literature. The work in this paper focuses on the research of durability test protocols of the fuel cell stack for the first time. The final conclusion will provide theoretical basis for establishing fuel cell durability test specifications and proposing life evaluation methods, and make a contribution to the long life research of vehicular fuel cells.

The over-exploitation of groundwater resources is a significant concern due to the potential risks associated with the depletion of this valuable freshwater source. Future planning must consider changes in groundwater availability and urban expansion which are critical for understanding urban growth patterns. This study aims to investigate the impact of land cover change on groundwater depletion. Further, the Land surface temperature (LST) analysis has been performed to find the spatial spread of urbanization and its impact on surface temperature. The Gravity Recovery and Climate Experiment (GRACE) data for groundwater storage monitoring and Landsat data for land cover and LST mapping have been used. The GRACE-based Groundwater Storage (GWS) anomaly has been correlated with Tropical Rainfall Measuring Mission (TRMM)-based precipitation data. The GWS is further cross validated with the groundwater monitoring stations in the study area and the correlation of 0.7 is found. The time series analysis of GWS and the land cover maps with a decadal interval from 1990 to 2020 has been developed to find the impact of groundwater change due to urbanization. The results demonstrate a rapid increase in groundwater depletion and urbanization rates over the past decade. The LST spatial pattern is increasing similarly with the study area’s urban expansion, indicating the temperature rise due to urbanization. The study highlights the limitation of effective policies to regulate groundwater extraction in urban areas and the importance of proper planning to ensure the long-term sustainability of freshwater resources.

AbstractUsing a low supply water temperature in heating conditions and a high water temperature during cooling can increase energy efficiency, use renewable energy sources, and provide a comfortable and healthy indoor climate. High temperature cooling and low temperature heating is achieved by reducing temperature difference in heat trans er and energy transportation process. The losses in temperature difference can be classified into three types: by heat/moisture exchange; by energy transportation through air/water circulation; by indoor terminal that releases heat/cooling to indoor condit oned space. The air handling process of HVAC system and indoor terminals are the key factor of reducing temperature differen e.Aiming at the losses in HVAC system, Annex 59, titled High Temperature Cooling & Low Temperature Heating in Buildings, is a new international cooperative work under the framework of International Energy Agency (IEA) Energy in Buildings and Communities (EBC). This paper introduc s the background, scope, objective, structure and deliverables of Annex 59. Annex 59 will try to present a new perspective and a new concept to analyze HVAC system in buildings. The goal of the Annex is to build up new concept of analyzing HVAC system from the perspective of reducing mixture loss and transfer loss and th n apply it in high temperature cooling and low temperature heating system.

Abstract Air change rate is a very important parameter for indoor air quality estimation as it influences the exchange of air pollutants between indoor and outdoor environments. Consequently, determining air change rate distribution is indispensable for assessment of a population's exposure to air pollutants. In this study, the annual and seasonal average infiltration rates (air change rate for window close conditions) of 180 representative residences were simulated using the multi-zone network airflow model (CONTAM) to understand the residential infiltration rate distributions in Beijing. The representative residences were selected by probability sampling based on building characteristics, including building type, floor area, number of rooms, construction year, number of floors, and building orientation. The results show that the annual average infiltration rates in Beijing range from 0.02 to 0.82 h−1 with a median value of 0.16 h−1. The empirical distributions of the annual and seasonal average residential infiltration rates in Beijing were provided. The annual average infiltration rates were also found to well fit a two-parameter lognormal distribution, the median and standard deviation of which is −1.79 and 0.62. Infiltration rates of 34 residences in Beijing were measured via the CO2 decay method, and the measured infiltration rates of residences matched the simulated distribution well. The differences between the simulated and measured infiltration rates are discussed.

Carbon metabolism of a chemical industrial park remains scarce in literature, due to overwhelming data collection workload and intricate interfirm flow examination. Based on five-year intensive data collection and verification, this research presents the findings of one-year static carbon metabolism in a typical Chinese fine chemical industrial park. As to the total direct carbon input (0.38 million tons), 32% concern chemicals production, while the remaining 68% are related to energy conversion. Three common metrics, carbon efficiency, C factor, and E factor are applied to assess the performance of carbon flows. Based on an analysis of 380 raw chemicals and 130 chemical products, performance of the three kinds of chemicals, pharmaceuticals, dyes, and other fine chemicals, and the chemical industrial park as a whole are considered and compared with similar industrial area, respectively. The carbon efficiency of chemicals production is 69%, while the other 31% ends up in waste. The interfirm carbon flow accounts for 3.4% of the carbon inputs in raw chemicals. Pursuing local environmental goals (i.e., abatement of odor, chemical oxygen demand, and solid waste) results in greater CO(2) emissions, which runs against protection of the global environment. Options to improve carbon efficiency were also discussed from three aspects. This study lays groundwork for quantifying greenhouse gas emissions, benchmarking carbon efficiency, and conducting life cycle assessment on the park level.

Study Region Mekong River Basin and surrounding areas. Study Focus: This study investigated the impacts of climate change on future meteorological and hydrological droughts in the Mekong River Basin and its surrounding areas. Our work is based on the output of five global climate models (GCMs) and simulations using the geomorphology-based hydrological model (GBHM) for the historical (1975–2004), near future (2010–2039), middle future (2040–2069), and far future (2070–2099) periods. The meteorological droughts in the study area were measured using SPI and SPEI, while the hydrological droughts were measured using SSI. New Hydrological Insights for the Region: The results suggest that droughts will generally reduce in the future over most of the study area, but will be more unevenly distributed with an eastward migration as compared to the historical period. Both meteorological and hydrological droughts will intensify in the near future, but will then reduce in intensity. Meteorological droughts will increase in the northeastern areas in the near future, followed by migration towards the south. Hydrological droughts showed similar aggravation followed by reduction, with upstream areas showing greater variability. In the general context of drought alleviation, southwestern China and the Mekong River estuary may suffer from a continuously increasing drought intensity in the future. This finding is based on 100-year extreme drought events.

Abstract The civil nuclear energy deployment in China is important for future “Nuclear Renaissance” of China and worldwide. Compared to the other nations that developed their nuclear power energy system in last century, China can take advantage of the research and mistakes made by those states with regards to the back-end of the nuclear fuel cycle (NFC). The spent fuel accumulated by decades of operations of civil nuclear power is today a big burden for the nuclear industry. China must carefully plan the NFC for a sustainable development of the nuclear energy with special consideration to closing the fuel cycle. The present paper addresses the NFC option and implication of a LWR reactors scenario development and of a fast reactor park developed after 2035 and 2050, and covers the historical development of nuclear energy in China (i.e. from the first criticality of the first reactor) to the year 2100. The paper studies the partition and transmutation strategy with the use of accelerator driven system (ADS) to burn the MA to understand the ADS impact on the NFC and to estimate the number and the necessary deploying schedule of the ADS reactors to limit the minor actinides stock build up. The code INFCIS developed by the International Atomic Energy Agency (IAEA) is used in the present study.