Performance evaluation and optimization of a novel solar-ground source heat pump system

• Two solar-ground source heat pump systems are designed and compared.
• SGSHPS(s) shows better performance than SGSHPS(r) in cold regions.
• It is conservation to operate system without heat pump in transition seasons.
• COPsys increases by 7.5% with the optimized collector area and length of GHE.
• COPsys is the best with the flow ratio of source and load side between 1.33 and 1.45.

This paper presents a novel solar-ground source heat pump system (SGSHPS) designed for an office building in Beijing for heating, cooling, and producing domestic hot water. An operation strategy of the system in transition seasons is proposed to keep the heat pump off and connect ground heat exchanger (GHE) directly to the heat exchangers of fan coils, as indoor conditioning terminal equipment. With the simulation tool TRNSYS, the important parameters of the system were optimized and the operation strategy was shown to be feasible. Two mainstream operation plural strategies in winter were analyzed and compared, and the system with GHE and solar collectors installed in series (SGSHPS(s)) showed better performance than SGSHPS(r) in cold regions.