Performance of a new active solar heat storage–release system for Chinese assembled solar greenhouses used in high latitudes and cold regions

Abstract

Various active solar heating systems have been developed to enhance the Chinese assembled solar greenhouse winter cultivation capacity by using renewable energy rather than traditional fossil fuel resources. These systems involve an efficient heat-collecting and transfer pattern, which solar energy can be converted into heat energy and flexibly utilized according to heating requirements, without unwarranted heating. To improve CASG thermal performance in high latitudes and cold regions, we modified the water-circulating solar heat collection and release system. The new structure was able to collect the solar radiation on the sheet during daytime to further generate heat through the magnetron sputtering plate. The collector also functions as a heating radiator during nighttime to protect crops from chilling injury in frigid weather. Field tests and economical analysis were performed to investigate the system’s thermal and energy-saving performance by analyzing several core parameters. Test results indicated that the average daily heat collection ratio of the system was 70.2%. The minimum nighttime indoor air temperature heated by the system was increased by 3.5 °C on average and maintained the temperatures above 9 °C after 2–3 cloudy days. The mean COP in heat collection and release phase were 8.2 and 2.4 over a period of 7 test days, respectively. The energy saving efficiency of the system was 44.1%. The novel system proposed in this study using thermal insulation structure and reasonable mass area ratio enables higher heat storage capacity and structure practicability. We demonstrated that the novel technology proposed in this study displayed energy saving characteristics. The new active solar heating system can be effectively used in high latitudes Chinese assembled solar greenhouse winter cultivation.