In the Ground Source Heat Pump (GSHP) System, it is important to improve the heat exchange rate of ground heat exchangers (GHE) and reduce the initial cost. The Semi-open Loop GSHPs which is proposed in this study, improves the heat exchange capacity by pumping groundwater from one GHE into other one and to generating artificial groundwater flow. In this research, a Semi-open Loop GSHP system was installed in Akita City, Japan to carry out field tests and certify its efficiency. This system comprises two ungrouted GHEs of 60 m depth with 5m distance. The pumping and injection of groundwater is done using a water pump connected to pipes to the depth of 15 m of the GHEs. The heating room is approximately 90 m2 and heated by 3 fan coil units which are connected to a 10 kW heat pump. The pumping and injection rate of groundwater was set as 0 (base case), 5 and 15 L/min and heating tests were performed for 7 days at each condition. The heating test in the base case with a pumping rate of 15 L/min showed that the COP (Coefficient of Performance) and SCOP (System COP) were improved by 8.3% and 3.5%, respectively. In addition, in the same case, average outlet water temperature of GHE was 5.5˚C higher than the base case. From these results, the Semi-open Loop GSHP system is expected to improve operational performance and reduce the initial cost.

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