Radiometric Characterization, Solar and Thermal Radiation in a Greenhouse as Affected by Shading Configuration in an Arid Climate

Energies

Ahmed M. Abdel-Ghany¹  Pietro Picuno³  Ibrahim Al-Helal¹  Abdullah Alsadon²  Abdullah Ibrahim²  Mohamed Shady¹ 

[1]Department of Agricultural Engineering, College of Food and Agriculture Sciences, King Saud University, P.O. Box 2460, Riyadh 11451, Saudi Arabia

[2]Department of Plant Production, College of Food and Agriculture Sciences, King Saud University, P.O. Box 2460, Riyadh 11451, Saudi Arabia

[3]School of Agricultural, Forestry, Food and Environmental Sciences (SAFE), University of Basilicata, via dell’Ateneo Lucano, n.10, Potenza 85100, Italy

关键词: shading nets;    solar;    thermal;    radiation;    greenhouse;    hot regions;   

DOI  :  10.3390/en81212404

来源: mdpi

【 摘 要 】

Shading the greenhouses is necessary in summer to reduce the solar radiation load. This however generates a considerable amount of thermal radiation heat load that needs to be removed via cooling systems. This study aimed to evaluate the effect of different shading configurations on the solar and thermal radiation in a greenhouse. Nets at four different locations were employed to shade the roof and side-walls of a polycarbonate, mechanically ventilated greenhouse. The spectral radiative properties of all these plastic materials were measured in short and long wave spectrum bands. The net solar and thermal radiations and air temperature were measured outside and inside two identical shaded and unshaded greenhouses. The results showed that external roof-shading is desirable, as it reduced the generated thermal radiation in the greenhouse by 21% and 15% during the day and night time, respectively and reduced the greenhouse air temperature during the day. The internal shading (roof and side walls) is undesirable, since it drastically increased the generated thermal radiation in the greenhouse by 147% and strongly increased the greenhouse air temperature during the day. Shading the side-walls is not recommended because it significantly reduces the transmitted solar radiation in the morning and afternoon (when the outside irradiance is low) and is useless at around noon when the outside irradiance is extremely high.

【 授权许可】

CC BY   
© 2015 by the authors; licensee MDPI, Basel, Switzerland.