Research on the heating performance of Chinese solar greenhouses achieved by the indoor compound parabolic collector and dual-source heat pump coupling system

Utilizing renewable energy to heat greenhouses can reduce the high emissions and heating costs resulting from energy consumption during greenhouse production. Among them, heat pump technology has the advantages of high energy conversion efficiency, low operating costs, and environmental friendliness. This study designs and installs the indoor Compound Parabolic Collector (CPC) and Dual-source Heat Pump Coupling System (CDSHP) to achieve air heating and energy transfer among multiple Chinese Solar Greenhouses (CSG). And an unheated greenhouse was set up for comparison. Optical simulation results show that in December, the average heat collection duration of the CPC reaches 6 h, with an average light reception rate of 80.47 %. Greenhouse heating tests indicate that the average daytime heat collection efficiency of the CPC is 80.8 %. Compared with Greenhouse 3, the indoor air temperature of Greenhouses 2 at night increased by at least 4 °C, the strawberry production increased by 7.1 %. During the test period, the system consumes an average of 111.3 kW h of electricity per day. The average Coefficient of Performance (COP) of the heat pump throughout operation is 2.3, while the average COP of the system is 5.0. The Payback Period (PBP) calculation for the system is 4.87 years, and the value of Levelized Cost of Energy (LOCE) is 0.070 $/kWh. This study utilized indoor CPC to collect heat and fully exploited the high-temperature air heat energy at noon, providing empirical evidence for dual-source heat pumps in the field of agriculture engineering.