ENHANCING RADIATION MANAGEMENT IN PASSIVE SOLAR GREENHOUSES: INNOVATIVE DESIGN EXPLORING THE SYNERGY OF FRONT COVER GEOMETRY AND SOLID TOP ROOF

The passive design of greenhouses is regarded as the key to solving the imbalanced space heating and cooling efficiency. Unfortunately, the lack of knowledge in their geometric variables—slope and curve of the outer envelope—prohibits the development of more energy-efficient greenhouses. This study proposes an innovative design for the greenhouse envelopes, including the front and top roofs, aiming at solving both the insufficient heating in winter and excessive heating in summer to ensure a passive and balanced energy environment. The overall geometry of the greenhouse, including the proposed steeper front roof and solid top roof design, is first introduced, followed by the mathematical model used for modeling the solar radiation and effective solar infiltration. Furthermore, a wide range of slope angles and curvatures at the slope for the greenhouse front roof are selected to be implemented in the model. By taking into account the varied latitudinal and seasonal factors, a comprehensive set of simulations is conducted to obtain the optimal slopes and curves at different set conditions. The top roof is also explored in a solid-finish design using a virtual case study simulated in Champaign, IL, USA. The independent and coupled impacts of slope and curve on the solar transmissivity and accumulation of solar radiation are evaluated and discussed. Non-negligible impacts were found in the design of the greenhouse envelope, as the optimal slope may impose up to 53% variation in winter and 93% in summer regarding the solar accumulation. The impact of curvature is found to be less significant, while it still influences the intake of solar radiation by approximately 10% in spring and summer in the simulated scenarios. The results obtained from this study may provide insights for the practitioners in the agricultural industry.