A study of fan-pad performance for a photovoltaic powered greenhouse in Saudi Arabian summer
, Al-Helal, I. M., Al-Abbadi, N. and Al-Ibrahim . 2004
The performance of a fan-pad evaporative cooling system for a photovoltaic powered greenhouse was investigated under extreme summer conditions of Saudi Arabia. Greenhouse air temperature, relative humidity and electricity consumed for cooling were studied in a Quonset greenhouse covered with corrugated fiberglassreinforced plastic sheets and producing cucumbers. Clogging pads due to salt buildup reduced the cooling performance and caused the cooling system to operate for longer duration, causing more power to be drawn from the photovoltaic system. As a result, the system tripped three times during the summer period for one to three days. During daytime, the average inside air temperatures with clogged pads was between 30°C and 51°C, and the relative humidity was between 8% and 30%. This adversely affected plant growth, leading to wilting of plants, especially when accompanied by high solar radiation levels (from 10:00 h to 16:00 h). Shade reduced the stress on plants, but air temperatures and relative humidity were far from the suitable ranges for good production practice. The average temperatures with shade ranged from 40°C to 47.5°C, and relative humidity ranged from 8% to 12%. Replacing pads clearly improved the greenhouse environment. Air temperature and relative humidity inside the greenhouse during daytime ranged from 28°C to 32°C, and from 39.3% to 44% respectively. The cooling efficiency for new pads was an average of 71%, with 8°C to 17.3°C reductions in ambient temperature. Electricity consumption with new pads was found to be around 22% less than that with old pads. Results also showed that electricity consumption increased non-linearly as the ambient temperature increased. The cooling system consumed the maximum electrical power (2.7 kW and 3 kW) at ambient temperature of 37°C or higher suggesting that the cooling system was in full operation. Shade had only a very minimal effect on the electricity consumption for the greenhouse cooling system.
The performance of a fan-pad evaporative cooling system for a photovoltaic powered greenhouse was investigated under extreme summer conditions of Saudi Arabia.