Impact of greenhouse roof height on microclimate and agricultural practices: CFD and experimental investigations

Greenhouses were known for their benefits in creating a stable and warm environment for plants to grow healthy. Meanwhile, air ventilation as well as optimal roof height of greenhouses is not well established in the literature as they are chosen based on only few experiences. As a remedy to this problem, the present work builds new correlations relating the roof height and the air velocity of ventilation on the temperature and vapor pressure deficit (VPD) thereby allowing a better control of these parameters for an optimal crop production. To achieve this goal, the study utilizes an experimental setup and a numerical model. The numerical model considers various elements, such as polyethylene, air, crops, and soil in combination, to evaluate their impact on the indoor climate. This paper presents a detailed analysis of how the greenhouse height ratio, designed as 'k,' can directly affect the microclimate within a polyethylene greenhouse, using a combination of numerical and experimental data. The study establishes strong correlations to capture the variations resulting from changes in the greenhouse height. In fact, a series of numerical simulations were conducted to assess the inlet velocities and height ratio on indoor temperature, velocity, and VPD. The comparative analysis reveals that the optimal conditions for the plant are only achieved in the lower part of the greenhouse for all considered greenhouse heights, where VPD = 2.2 for k = 1 and VPD = 1.8 for k = 4. Therefore, this study illuminates the impact of greenhouse height on greenhouse climates and underscores the significance of precise modeling and control to enhance agricultural practices in Tunisia.