Research On Schemes And Operation Strategies Of Energy Storage-Geothermal Coupling System For Office Building Heating

According to the requirement that the inlet water temperature of reinject well should not be higher than 20℃in the heating code,the heat pump should be used in the geothermal heating system to meet this requirement.In order to reduce the cost of geothermal heating,this paper studies geothermal heating system coupled with energy storage for office building heating,optimizes the coupled heating system based on four operating strategies combined with time-of-use electricity prices,and analyzes and summarizes the influence of different time-of-use electricity prices and equipment prices on the optimal value of the system.Firstly,a geothermal heating system coupled with energy storage is proposed for the office building heating in Xianxian county,Hebei Province.And the operation characteristics and operating strategies of the system are analyzed.Secondly,MATLAB software was used to establish mathematical models for water pump,heat exchanger,heat pump,energy storage tank and other system components and devices under different operating strategies,and simulated the hourly heat load of the system.Then,the improved genetic algorithm was selected as the optimization algorithm,four parameters were selected as the decision variables:the energy storage ratio of the energy-storage tank,the upper limit of temperature of the energy-storage tank,the end temperature difference at low temperature side of the high temperature heat exchanger and the maximum temperature difference of the heat pump system,and the levelized energy cost(LEC)was used as the objective function to optimize and analyze the coupled heating system.Finally,the model is verified with the test data of the coupled heating system in the geothermal demonstration base of Xianxian county,Hebei Province.Furthermore,the model is used to optimize different operation strategies and different price scenarios,and the technical economy of the system is evaluated by comparing the optimization results.The results show that the coupling of the storage tank can save more than 25%of the operating cost in the existing conventional geothermal heating system,and strategy 2 can save 29.61%,which is the best performance;When the system is optimized considering the investment cost,strategy 3 is the best,and strategy 3 can achieve better results even with a smaller storage tank;In cases where coupled system are suitable,the optimal energy storage ratio is not more than 55%;When the peak-valley price difference is more than 0.566 CNY/kW·h or the energy storage tank price is lower than 900 CNY/m~3,the coupled heating system has better technical economy than the conventional heating system;The optimal temperature difference of water tank heat storage should not exceed 12℃.This study has guiding significance and reference value for the design,operation and practical application of low cost energy storage-geothermal coupled heating system.