Determining the optimum span of a solar greenhouse

The span of a solar greenhouse is a crucial parameter determining its architectural space form characteristics, which in turn directly influences the passive solar energy utilization and light-heat environment within the greenhouse. As a result, building on prior research concerning the optimal orientation and height-span ratio of solar greenhouses, this study delves into the key factors affecting the optimal span and its evaluation indices. Global solar radiation is broken down into direct radiation and diffuse radiation, both of which serve as input parameters for Energy Plus weather files. Additionally, the soil temperature calculation model within a solar greenhouse is employed as the input condition for "Ground temperature" boundary conditions in Energy Plus. The field test demonstrates the efficacy of the Energy Plus model. Taking the calculation results into account, this research provides a comprehensive analysis of the impact of outdoor air temperature, solar radiation, north wall height, heat storage capacity, and soil temperature inside the greenhouse on the thermal environment when the span is altered. A simplified calculation model for determining the optimal span of solar greenhouses across various latitudes in China is proposed based on the optimal span evaluation index. Field tests confirm the effectiveness of this calculation model. This study enhances the design and calculation methods for optimal space form characteristic parameters of solar greenhouses. Furthermore, it offers an analytical method reference for the optimal design of solar greenhouses, efficient construction of thermal environments, and intelligent management and control.