| With the development of clean heating,ground source heat pump is widely used in northern China,and it has become one of the main clean heating technologies in rural primary and secondary schools.Due to the climate conditions and the operation characteristics of schools,the load difference between winter and summer is large.Therefore,the performance of heat pump deteriorates after long-term operation.Using solar energy to supplement soil heat can effectively solve the problem of soil heat imbalance.But at present,the design and operation method of solar assisted ground source heat pump system is still extensive,which leads to the poor actual operation effect and poor economy of the system.Therefore,this paper investigates the solar assisted ground source heat pump system in rural primary and secondary school in the north,and then establishes the simulation model and optimizes its design and operation.This study aims to improve the energy efficiency and economy of the system in practical application,and promote the further promotion of clean heating technology of ground source heat pump.Firstly,this paper combs the building form,thermal performance and operation mode of primary and secondary schools in northern rural areas through literature research.The typical winter and summer operation conditions of solar assisted ground source heat pump system in a middle school in Daxing District of Beijing were investigated and measured,and the problems in operation regulation and design of the system were analyzed.In order to explore the perennial operation performance of the system,TRNSYS is used to establish the system model,and the measured data are used to verify.Then,the problems existing in the current design and operation of the system are optimized.The operation optimization includes adding the start-up and stop control of each equipment in the system,and using Trn Opt to optimize the control temperature difference of solar collection and soil heat suppiement.In the aspect of design,the solar collector area was optimized to make the annual average ground temperature change less than 1% after 15 years of operation,and the soil reached heat balance.On this basis,the two series systems are compared.The system that the outlet water of the unit first goes through the buried pipe and then through the water tank can obtain higher outlet water temperature,which is conducive to improving the operation efficiency in winter.However,when the order of buried pipe and water tank is changed,the outlet temperature of heat source is stable,which is beneficial to summer operation.After optimization,the coefficiency of performance of the two systems are increased by 23%and 23.4% respectively.The current collector selection method lacks the consideration of the actual energy efficiency of heat pump and soil recovery capacity.This paper studies the collector selection method based on the heat balance method.Through single factor analysis,orthogonal experimental design and variance analysis,the results show that the ratio of cooling load to heating load and soil temperature have significant effects on the area of solar collector,accounting for 53.1% and 35% respectively,while the comprehensive thermal conductivity of soil has little effect,accounting for 5%.The model of collector selection was obtained by stepwise linear regression analysis of the experimental results.On the premise of soil heat balance,shortening the heat supplement period and increasing the heat collection area will also affect the system economy and energy efficiency.In order to achieve better operation effect,this paper sets 4 kinds of heat supplement periods for different ratio of cooling load to heating load.By analyzing the boundary heat flow of soil regenerator,the seasonal characteristics of solar heat supplement are studied,and the economy is analyzed by comparing the static recovery period of each working condition. |
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