Influence of Shading on the Performance of a Greenhouse Evaporative Cooling System PDF

Keywords

Greenhouse, shading, influence, performance cooling System, temperature, humidity

Abstract

This research was conducted to study the effect of shading materials on greenhouse environment including inside temperature and relative humidity, and water and electricity consumption for cooling under Riyadh conditions. The study was performed on five greenhouses cooled by the fan and pad evaporative cooling system. The greenhouses were covered with single layer polyethylene. Four greenhouses were shaded with green plastic nets on the outside surfaces of covers. Shading levels were 55%, 65%, 70% and 80% according to the factory specifications. The fifth greenhouse was without shade for the purpose of comparison. Experiments were performed in two periods: the first period was from October 1 to October 30, 2000 (moderate summer conditions), and the second period was from July 16 to July 24, 2001 (extreme summer conditions). The results indicated that shade had no significant effect on inside air temperature during moderate conditions (P=0.05). But, inside relative humidity with shading levels of 55%, 70% and 80% was significantly higher than that without shade. During extreme summer conditions, shade significantly reduced air temperatures and increased relative humidity The 80% shade significantly reduced the consumption of water and electricity during moderate conditions by 16% and 19.3%, respectively. The 70% shade significantly reduced the consumption of electricity by 12.7%. Shade had no significant effect on the consumption of water and electricity during extreme conditions (P=0.05). It was shown that water and electricity consumption during extreme conditions were higher than those of moderate conditions. The increase rate of water consumption ranged from 79 to 112%, while consumption of electricity increase ranged from 12.7 to 36%.