Optimal Design Of A Solar Assisted Ground Source Heat Pump System With Seasonal Thermal Energy Storage In Cold Area

With the development of economy and the improvement of people’s living standard,the building energy consumption is increasing year by year,and the environmental problems are increasingly serious.The green and low-carbon transformation of energy has become the key to reduce the building energy consumption and alleviate the environmental problems.Based on the building application of renewable energy,this thesis studies the comprehensive utilization technology of geothermal energy and solar energy,and establishes a solar assisted ground source heat pump(SAGSHP)system with seasonal thermal energy storage.The system has many functions such as heat collection,heat storage,heating and cooling.In order to determine the optimal system configurations and parameters,the contents of this thesis are as follows:First of all,this thesis establishes a typical first class office building model(the built-up area of single building≥10000m~2)in cold area,and applies De ST-c simulation to obtain the cooling and heating loads of this building in cooling and heating season.The system parameters such as solar collector area,number of buried pipes,heat pump type,circulating liquid flow rate are determined.And three kinds of cross season heat storage SAGSHP systems are designed and constructed,indirect heat storage system with heat storage tank,direct heat storage system without heat storage tank and direct heat storage auxiliary heating system without heat storage tank.Secondly,TRNSYS software is used to simulate the independent ground source heat pump system and the three systems mentioned above,in order to find the optimal system configuration to meet the heating,cooling and hot water requirements of the first class office building.The results show that the direct heat storage auxiliary heating system provides excellent performance,the average COP in heating season is 3.54 and the average EER in cooling season is 5.49.In addition,the direct heat storage auxiliary heating system also shows the best environmental and economic performance.The carbon emissions reduce by 55%compared with the conventional energy system.And the system provides the shortest payback period compared with other systems.Thirdly,this thesis uses the relevant operation data of the renewable energy system of the office building of Tianjin architectural design institute to verify the simulation results of the TRNSYS model of the direct heat storage auxiliary heating system to ensure the reliability of the simulation model.Results show that the error values of the simulation system and the measured system are in a reasonable range,the simulation model is reasonable and feasible.At last,in order to reduce the cost of the system and improve the efficiency of the system,several parameters such as collector area,domestic water tank capacity,heat storage time and heat pump power are optimized.On the premise of ensuring the unit to fulfil the heating and cooling requirements of building,the hot water guarantee time of the system is increased from 67%to 86%in the whole year.The average COP of the heat pump is increased to 3.98,and the average EER is increased to 5.89;the average investment recovery period of the heat pump is shortened to 4.61 years.This thesis provides some guidance and reference for the SAGSHP system with seasonal thermal energy storage in cold areas,which is conducive to the promotion and application of the system in cold areas.