Performance evaluation of a hybrid ground source heat pump system with thermal recovery and intermittent operation strategies

This study proposed a hybrid ground source heat pump (GSHP) system to address energy efficiency and thermal imbalance issues in conventional GSHP systems. Both open-loop and closed-loop ground heat exchangers were integrated into the system with a thermal recovery storage tank, which was designed to maintain the heat pump inlet temperature above 5 °C by utilizing phase change material capsules and thereby prevent performance degradation. Intermittent operation strategy was applied to circulation pumps to improve operational efficiency under varying loads. The system was installed in a demonstration building, and field experiments were conducted to evaluate its thermal performance, power usage, coefficient of performance (COP), and economic feasibility. The mean COP reached 3.18 during cooling and 3.08 during heating. Power consumption associated with the heat pump and circulation pumps decreased by as much as 48.1% and 78.8%, respectively. Annual electricity costs decreased by 71.7%, and net present value ratio analysis indicated a payback period within 10.6 years. Environmentally, annual emissions of CO 2 , SO 2 , and NO x were estimated to be reduced by over 67%. The proposed hybrid GSHP system effectively improved energy performance, cost-effectiveness, and ecological impact, demonstrating strong potential for application to carbon-neutral buildings, smart farms, and local energy systems.