Optimization of Greenhouse Cooling Strategies: Performance Analysis of Ventilation and Evaporative Cooling Across Different Climatic Regions in Lebanon.

Inhalt:
Improving greenhouse climate control increases agricultural productivity while reducing energy consumption. It makes effective ventilation and evaporative cooling strategies essential for sustainable year-round production. In Lebanon, three diverse agricultural regions are identified: Akkar (Coastal: hot and humid), Zahle (Bekaa Valley: hot and dry), and Aley (Mount Lebanon: warm and humid). This study identifies the cooling period using a climograph and discusses cooling systems. In the present paper, a thermal model is developed to predict internal greenhouse temperature in summer under different ventilation rates (2–40 air exchanges per hour) with and without shading, initially neglecting crop transpiration. The predicted temperature is then used to estimate leaf temperature under various ventilation rates and inside relative humidity (60–90%), showing the inefficiency of ventilation for cooling in June and July. The feasibility of the fan and pad evaporative system is evaluated by computing the temperature and relative humidity profiles inside the greenhouse, on May 25(exp th), June 25(exp th), and July 25(exp th), with a ventilation rate of 20 h^-1. Performance in the three regions demonstrates that the suggested system is effective in Aley (28deg C, 80%-RH) but not in Akkar (33deg C, 80%-RH) and Zahle (33deg C, 50%-RH) in July. Whereas, in June, it is effective in Aley (25deg C, 70%-RH), Zahle (30deg C, 60%-RH), and Akkar (30deg C, 70%- RH) with proper suggestions. Furthermore, the system was proven effective in May in all regions. The analysis demonstrates the operational limits of evaporative cooling, offering potential future studies on integrating it with cost-prohibitive heat pumps for optimal greenhouse climate management.