Thermal performance of greenhouses with a built-in solar distillation system: experimental study

An experimental investigation is presented of the thermal performance of an agricultural greenhouse (GH) with a built-in solar distillation system. A set of solar basins with saline water was placed on the greenhouse roof to reduce the GH cooling load and to produce the required fresh irrigating water by solar distillation. The ventilation air enters the GH through an evaporative cooler for cooling in summer (and hot days), and is partially recirculated for heating in winter (and cold days). The experimental work was carried out and the GH was constructed at the King Abdul Aziz University, the city of Jeddah, Saudi Arabia. The system transient performance (temperatures, relative humidity, and water productivity) is presented for the summer of July 2004 in Jeddah. Measures to improve GH performance are also highlighted.

1. Experimental investigation of the thermal performance of agricultural greenhouses with a built-in solar distillation system was carried out. The combined GH–solar distillation system utilizes abundant solar energy in hot climates (above that required for the photosynthetic process) to partially reduce the GH cooling load in summer, and to partially produce required irrigation water by solar distillation. The experimental work was carried out for a GH constructed at the King Abdul Aziz University in the city of Jeddah, Saudi Arabia. 2. The system transient performance (temperatures and humidity inside the plant growth zone and water productivity) was presented. Within the summer climatic conditions of the city of Jeddah, the results indicated that the GH inside temperatures could be 8–10 degrees (at GH inlet) and 3–6 degree (at GH outlet) below ambient temperature. The GH inside relative humidity was found to vary from 20% to 35% above ambient conditions, within the comfort zone of plant growth. 3. Some measures to improve the productivity of the GH solar distillation were highlighted.