A Two-Factor Thermal Screen Control Strategy for Chinese Solar Greenhouses in High-Latitude Areas

Abstract

Covering thermal screen on the front roof is one of the most general methods to improve the thermal performance of the solar greenhouse in China. Thermal screen control, however, is operator-dependent and based on empirical strategies. In order to more effectively manage the thermal screen, an optimal control method based on solar radiation and temperature difference between indoor and outdoor was established. The influence of different factors on the control of greenhouse thermal screen is systematically analyzed and the control function of the greenhouse thermal screen was calculated. The empirical control formula was established based on simulation which lasted for 62 days. As a result, the two-factor control method can significantly improve the air temperature when the thermal screen is controlled, and it can increase the average air temperature by 0.53 °C. Comparing with temperature difference, solar radiation has a greater impact on the control of thermal screen. The control method based on temperature difference and solar radiation can save 7.2% energy in winter. The research can provide reference for energy saving and automatic control of Chinese solar greenhouse.