Experimental and Numerical Study of an Active Solar Heating System with Soil Heat Storage for Greenhouses in Cold Climate Zones

Root temperature is an important ecological factor affecting plant growth. A solar greenhouse with an active solar heating system was built in Jinan, in the cold climate zone of northern China. Experiments encompassing the complete cycle of heat collection, heat storage, and heat release were carried out. Using the experimental data, the numerical simulation of soil heat storage with a variable heat flow was executed using the ANSYS (ANSYS Inc., Pittsburgh, PA, USA) Fluent software. Soil temperature fields were studied on typical sunny days and typical cloudy days in the transition season and winter. The solar collector efficiency and coefficient of performance of the system were investigated. The applicability of this active solar soil heating system with soil heat storage for cold areas was evaluated. The results showed that the system effectively maintained suitable ground temperatures to prevent plant growth inhibition caused by low ground temperatures in winter. During the experimental period, the solar collector efficiency was 47% and the system’s coefficient of performance was 67.70. The thermal performance of the system was much better than a traditional energy system. This study showed that this active solar heating system with soil heat storage is an economic and feasible way to increase soil temperatures in solar greenhouses in cold areas.