Performance investigation of a combined solar thermal heat pump heating system

• A combined solar thermal heat pump heating system was studied.
• The performance simulation model was built using the TRNSYS software.
• The impacts of major parameters were analyzed.
• The optimal parameters were essential to ensure the performance of the system.

In this study, a combined solar thermal heat pump system with seasonal energy storage was proposed for both space heating and domestic hot water (DHW) in cold climate area. Using the TRNSYS software, the proposed system was modeled and compared with a conventional space heating system. Moreover, the influence of major parameters on system performance was analyzed. The investigation results show that the average COP of the total system reaches 3.7 during heating months. On average, the monthly COP for space heating is about 3.2. Compared with the traditional space heating system, the system performance is improved obviously and the monthly energy saving ratio for space heating is about 52%. It is also found that the most appropriate dead-band temperature of the air-to-water heat pump unit is −7 °C, the optimum storage factor should be within the range of 0.5 m3/m2 to 0.8 m3/m2 and the solar collector area is proposed to be in the range of 130 m2–160 m2. With the specifically proposed parameters, the system performance for space heating is improved by 12.8% compared with the original design. It is concluded that the properly designed solar thermal heat pump heating system can operate effectively and reduce tremendous energy consumption compared with the traditional heating system used in cold climate buildings.