Study of the Thermal Environment and Marginal Effects of a Sunken Solar Greenhouse

Abstract

A sunken solar greenhouse is a unique structure used in China that has good thermal performance and a low cost. To explore the thermal environment and the marginal effect area under the trellis membrane in a sunken solar greenhouse, daytime heat absorption and nighttime exothermic models of the greenhouse were established based on existing theories and hypotheses. An experimental study of the three-dimensional thermal environment of a solar greenhouse was also conducted in the Jinzhong Basin of Shanxi Province. The daytime heat absorption model described how the internal thermal environment of the greenhouse changes in three dimensions, while the nighttime model calculated the amount of heat released at night. The results showed that the rate of change in the maximum temperature difference along the height direction in the greenhouse was 13 times that along the vertical direction, and three times that along the horizontal direction. We also observed that the marginal effect area under the membrane varied over time and by month. The minimum value of the marginal effect area occurred at the middle cross-section, spanning the middle position of the greenhouse, and the maximum height was 2.7 m. The results of this study can provide theoretical guidance and experimental data for the thermal environment of greenhouses of the same type in the Jinzhong Basin of Shanxi Province, thus providing a basis for environmental regulation and low-temperature margins in greenhouses.