Thermal performance of a novel underground energy migration system for greenhouse

The progression of Chinese solar greenhouse is shifting from an integrated insulation and heat storage system to a separated configuration. Retaining a significant amount of surplus air thermal energy during the day, it can be stored and released at night to meet heating demands. To effectively utilize the surplus air thermal energy, an underground energy migration system is proposed for storing it. The thermal environment of the greenhouse is analyzed in experiments after applying the system, and the required thermal performance for the system’s heating is calculated using the greenhouse’s thermal balance. A computational fluid dynamics method is employed to optimize the system while also determining the system’s impairing effect on the greenhouse’s thermal environment. The findings suggest that the insulation of heat storage units must be externally maintained to prevent soil interference with the system’s thermal performance. The optimal airflow rate for heat storage was 2 ∼ 2.5 m/s, and 2.5 ∼ 3 m/s for heat release. The average air temperature of greenhouse decreases 1.80 °C in daytime and increases 2.14 °C in nighttime by the underground energy migration system. Meanwhile, the heating coefficient of performance reaches 5.14. The system provides new ideas and methods for the recycling of clean energy in greenhouses.