Performance study of solar energy interstage auxiliary two-stage compressed air-source heat pump water heaters

Different solar irradiance has different energy grades. The existing integrated solar-energy and air-source heat pump systems can not operate efficiently at different solar irradiance. In this paper, an integrated system that can operate efficiently in a wide irradiance range is proposed, that is, the solar collector is placed in the middle injection branch of the two-stage compressed heat pump to form a solar energy interstage auxiliary two-stage compressed air-source heat pump system, and it is used to produce domestic hot water. The system simulation model is established, the system operating characteristics under different irradiance, outdoor temperature and compressor volume ratio are numerically simulated based on MATLAB software, the influence of each parameter on the system operating characteristics is analysed, and the optimal volume ratio is obtained.