Performance study of solar air collector-air source heat pump system inside the greenhouse

During the process of heating greenhouses, the phenomenon of inadequate heating installations is widespread. To address this issue, this paper proposed a solar air collector-air source heat pump (SAC-ASHP) system for greenhouses, combining solar technology with heat pump (HP) technology to provide sufficient heat during continuous cloudy days and winter. The heating capacities of the system on sunny, cloudy, and overcast days were 100.2 kWh, 112.3 kWh, and 157.8 kWh, respectively. The corresponding power was 30.1 kWh, 36.1 kWh, and 53.6 kWh. The coefficient of performance (COP) of the single air source heat pump (ASHP) for these days was 3.4, 3.2, and 3.0, respectively, while the COP of the solar heat pump (SHP) was 4.0, 3.5, and 3.1. Additionally, greenhouse employed heat and moisture recovery for humid air, aiming to provide a suitable environment for plant growth around the clock while conserving energy. The heat collection in the heat and moisture recovery combined HP mode was 66.7 % higher than in the heat exchanger (HE)-fan mode. This experimental study investigated the operational performance of the system in dynamic environments, revealing the stability of the system for greenhouse heating in cold regions, and providing new research ideas for greenhouse heating.