The field test and optimization of a solar assisted heat pump system for space heating in extremely cold area

• A solar assisted heat pump system was built in extremely cold area.
• The system has been applied in a practical engineering in Daqing, China.
• The system was simulated by TRNSYS and the parameters were optimized.
• The heating cost of SAHP decreased 55% compared with conventional heating system.
• The study has some reference for the design of SAHP system in actual project.

As a kind of sustainable energy source, solar energy is becoming highly valued. Especially in extremely cold areas, the amount of energy consumed for space heating is huge, and the conventional coal heating has polluted the environment seriously, therefore solar heating is significant on both energy and environment conservation. In this study, a solar assisted heat pump (SAHP) system was investigated for space heating under extremely cold climatic condition. The system principle and operation modes was presented, and then the project profile and design procedure were introduced, and finally the system performance was evaluated by field test on typical winter days and modeling via TRNSYS simulation environment. The results show that the solar collector efficiency was 51%, and the solar fraction can reach 66% in December. Economic analysis was also performed and the heating expenses for the present SAHP system was 18 RMB/m2. Finally, the temperatures of solar energy for both direct heating and storage and only for direct heating (T1A and T1B) were simulated and optimized, which have important significance on the operation time of different operation modes.