Transient performance characteristics of a hybrid ground-source heat pump in the cooling mode

The objective of this study is to compare the transient performance characteristics between a ground-source heat pump (GSHP) and a hybrid ground-source heat pump (HGSHP), accounting for the degradation of the ground thermal condition during long-term operation. A heat storage bath for the ground heat exchanger (GHE) was adopted to simulate the transient characteristics of the ground thermal condition. In transient state, the performances of the HGSHP and GSHP were measured by changing the fluid flow rate (FFR) through the supplementary plate heat exchanger (SPHE) and the set-point temperature of the hybrid operation. The optimum FFR and the optimum set-point temperature of the HGSHP were determined as 8 kg min−1 and 30 °C, respectively. At the optimized conditions, the average COP of the HGSHP increased by 7.2% compared with that of the GSHP.