Performance Investigation Of Ground Source Heat Pump System Coupled With Thermal Energy Storage Devices

At present,ground source heat pump system has been widely applied in China and abroad.In this paper,a compound energy system which combines the GSHPS(ground source heat pump system)and the thermal energy storage system(TES)was studied.The heat transfer model of BHE(borehole heat exchanger)was simulated by FLUENT to research the variation of soil temperature around the borehole under different cases.The results show that reasonable load distribution of borehole exchanger to develop intermittent operation is good for the soil temperature restoration,which could not only stable the temperature around the BHE,but also improves the heat fluctuation in the soil.Meanwhile,TRNSYS was used simulate the compound energy system and conventional GSHPS,the average soil temperature of those two system under shortterm and long-term operation was compared,which shows the compound system could reduce the temperature fluctuation in the soil and maintain the heat balance in the soil.Through changing the operation strategy of the compound system,the soil temperature change,the outlet water temperature of BHE and COP(coefficient of performance)of the heat pump unit under different strategies were analyzed.An engineering project was built for experiment.From the experiment process,it's showed the compound system has a higher COP than the common GSHPS by 0.37 in winter and 0.04 in summer.Due to the price policy of off-peak electricity,the compound system could save 35.2% of the running cost in winter and 18.3% in summer than that of common GSHPS.In some cases,the compound system also has a lower initial investment.In conclusion,based on the simulation and experimental studies of the compound system,it's proved that the compound system has many advantages in operation compared to the common GSHPS.The results provides a theoretical and experimental basis for the promotion and application of the system.