Experimental investigation and optimization of a ground source heat pump system under different indoor set temperatures

A constant temperature and humidity air-conditioning system driven by a ground source heat pump (GSHP) was designed and constructed in an archives building. The imbalance of earth energy caused by the difference of load between heating mode and cooling mode affects soil temperature, which may result in poor efficiency of the GSHP system. Therefore, the system was optimized based upon two aspects. Firstly, the heat recovery technology was used to reheat the air inside the air handling unit (AHU), which aimed at alleviating the imbalance of earth energy. The experimental results showed that the imbalance of earth energy for the system during the whole year was 16.3%, discharging about 33.7% less heat to the soil compared with the system without heat recovery technology. Secondly, the set value of indoor temperature was optimized for the purpose of further reducing the imbalance of earth energy during the system operation. It was shown that the heat transfer between the ground heat exchanger and soil was distinctly affected by the indoor set temperature. Considering the long-term stability of soil temperature and energy conservation of the system, higher value of indoor temperature was suggested to be set on condition that the indoor environment could be met. Both the design method of heat recovery and the optimization of indoor set temperature are meaningful for the suitable utilization of GSHP systems in cooling-dominated buildings.