Study on soil heat storage performance and operation strategy of new integrated HST-GSHP system in different cold regions

Abstract

Heat source tower (HST) can absorb and transfer the total heat of air into soil through borehole heat exchanger (BHE) in summer, which is a potential and effective method to eliminate soil thermal imbalance of ground source heat pump (GSHP) in cold regions. In this paper, a new integrated system of HST and GSHP (HST-GSHP system) and its operating modes were proposed for soil heat storage in non heating season. Based on modeling and calculation, soil heat storage performance, operating strategy and economy analysis of the HST-GSHP system were studied. The results show that the soil heat storage of the system is concentrated in the middle of non heating season, and only from HST-BHE mode in Mohe and mainly from HST-BHE&GSHP mode in Changchun and Lanzhou. The air energy absorbed by HST accounts for 100%, 59.7% and 33.2% of the total soil heat storage in Mohe, Changchun and Lanzhou respectively. The optimal operating periods of the system are from May 30 to September 4 in Mohe and from May 30 to September 11 in Changchun, and from May 29 to June 5, from June 21 to September 4 in Lanzhou. The HST can be used for soil heat storage in Mohe and Changchun effectively, while indirect heat exchanger is more suitable for soil heat storage in Lanzhou and the optimal operating periods are from April 28 to May 4 and from May 8 to September 10. Compared with the boiler and split air conditioner system and air source heat compensator integrated with GSHP system, the energy-saving rate of the HST-GSHP system is 47.6% and 31.2% respectively and the HST-GSHP system is more economical in most cases.