Optimum design and orientation of a greenhouse for seasonal winter drying in Morocco under constant volume constraint

Abstract

In this work the solar radiation intercepted by two commonly used greenhouses, namely the even-span and uneven-span shapes, was optimized under a constant volume for the first time. The optimal shape and orientation of the greenhouse was determined for drying purposes during the winter period (from 1st October to 31st March) by varying the two decision variables (orientation of the greenhouse and its roof tilt angle) with a small step of 1°. The seasonal solar radiation transmitted inside the greenhouse was computed for each configuration and orientation in order to identify the optimal design and orientation. The solar energy transmitted was evaluated by taking into account the incidence angle dependence of the transmittance of the greenhouse cover (polycarbonate). The results showed that the uneven–span greenhouse with a roof tilt angle of 45° and an orientation of −80° (10° from the E-W orientation) was optimal for capturing the maximum solar radiation compared to all other configurations, shapes and orientations for Marrakech Morocco. This incidence angle dependence of the transmittance did not significantly affect the optimal shape and orientation but reduced the solar radiation inside by 10% compared to the reference case of normal incidence transmittance. It is estimated that the optimum configuration (shape, orientation) will enable to reduce the heating costs of the greenhouse system during the winter season by $ 90 per square meter of the greenhouse floor. This model can be easily extended to assess the total solar radiation intercepted by all such greenhouse systems under different weather conditions.