Construction And Performance Research Of Multi-source Distributed Energy Exchange System For Different Regions

Carbon emissions from heating in the building sector in China account for 26%of the national carbon emissions in 2021.In order to further save energy and reduce carbon,distributed energy systems have received widespread attention in the energy sector for their flexibility,efficiency and cleanliness.At present,there is a lack of research on the construction method of distributed energy system in domestic and international research,which leads to the distributed energy system cannot achieve better energy saving and carbon reduction effect and thus becomes one of the main technical bottlenecks in this field.In response to the above-mentioned situation,this study proposes a distributed energy exchange system based on the existing results of distributed energy systems.Based on the actual requirements considered in engineering projects,the theory of constructing multi-source distributed energy exchange system is proposed,and the scientific issues involved in distributed energy exchange system are studied.The study firstly introduces the concept,characteristics and principles of distributed energy exchange systems.Based on the operation principles and energy-mass balance of electric heat pump,solar collector,fuel cell and plate heat exchanger,a thermodynamic model of multi-source distributed energy exchange system is established.The theoretical study of the construction of distributed energy exchange system is carried out with the objective of optimizing the total annual cost of the system.The heat pump should be placed in the low-temperature section of heat production,the solar collector should be used in the medium-temperature section,and the plate heat exchanger should be placed in the high-temperature section when the distributed energy exchange system is used to supply heat to customers.Based on the construction theory proposed in this study considering different tariff types and solar energy resources,a multi-source distributed energy exchange system process applicable to different scenarios is finally proposed.In order to reveal the performance characteristic laws of multi-source distributed energy exchange systems,distributed energy exchange systems in three representative regions,Northeast,North and Central China,are studied.Among them,system Ⅰ connects solar collector and plate heat exchanger,heat pump and fuel cell in series,system Ⅱconnects solar collector and heat pump,fuel cell and plate heat exchanger in series,and both series circuits of system Ⅰ and system Ⅱ are connected in parallel.The system is designed to heat a community with a heating area of 100,000 m2 and to determine the solar collector laying area according to the actual site conditions of the community.When analyzing the system performance parameters,the COP of System Ⅰ is higher than that of System Ⅱ,with the highest difference of 1.48 and 1.12 between Northeast and Central China,while the difference between the two values is smaller in North China,which means that System Ⅰ is more suitable to meet the heating demand of Northeast,North and Central China by fully considering the parameters of system power consumption and fuel cell power.If we consider the economy and environmental protection,compared with system I,the annual operation cost and annual carbon emission of system Ⅱ in Northeast and Central China are lower,which are 1,469,600～386,700,870,800～279,500,1,494.73～418.86 tons and 886.98～300.62 tons respectively,and the annual operation cost and annual carbon emission of system I in North China are lower.Therefore,System Ⅱ is more suitable for heating in Northeast and Central China while System Ⅰ is more suitable for heating in North China.Since the circulation performance of heat pumps varies greatly in the system and thus affects the energy consumption level of the whole system,this study investigates in depth the circulation media of the key units of heat pumps to improve their circulation performance.The five media were selected to meet the selection criteria,namely R1234ze,R152a,R1233zd,R1234yf and R161,and the performance of R1233zd was found to have the highest COP of 6.39 and lower exhaust temperature and condensing pressure under the same operating conditions.R1233zd was selected as the circulating mass for the heat pump in a distributed energy exchange system and compared with R134a in a community in North China with a heating area of 100,000 m2.The results showed that the COP of the system with R1233zd increased by 4.05%to 5.68%when the outdoor temperature varied from-10 to 5℃.The monthly operating costs and monthly carbon emissions were reduced by 167,900～228,500 and 69.99%～73.87%,respectively.It has a better performance advantage.