Due to the increase of the renewable energy and the energy-saving technologies in building, heat pump system using ground heat has been concerned. Ground source heat pump system takes advantage of the stable ground temperature to achieve energy savings and to reduce CO2 emission. However, after a long heating period the soil temperature would decrease and the COP of system can be affected directly. This paper suggests a ground source heat pump system assisted with solar thermal storage which can not only keep the balance of the soil effectively, but also gets a high COP. And in order to grasp the characteristics of the system, simulations were conducted by TRNSYS 17 with different conditions. As the results can be drawn as follows;
(1) The ground heat pump system assisted with solar thermal can effectively keep the balance of soil temperature. And under the same operation conditions, the performance of SAGHPS is better than that of GHPS. Compared with GHPS, during the whole operation time, the heat exchange rate, heat source and heat pump COP of SAGHPS are increased by 28.1%, 21.9%, 9.3%.
(2) With the increase of the collector area the heating performance of system upgraded, but the investment costs also increased relatively. As the result of the LCC assessment, when the solar collector area increased from 50m2 to 90m2, the payback period of SAGHPS would be in the range of 10 to 12 years.
(3) Different from the other ways, using a high thermal conductivity grouting can not only increase the performance of heat pump, but also increase the solar storage ratio.
(4) In different location, because of the climatic differences the performance of system is also different. In subtropical area (Shanghai), system got a better performance than that of cold area (Sapporo), However, in cold area system got the best solar storage radio, it is 55.4%, 0.6%, 6.5% higher than that of Seoul and Shanghai.
(5) In the next research stage, the simulation results will be verified by demonstration experiment, and in order to establish the optimum design method of the suggested system, more case studies will be conducted.