Predicting the Cooling Potential of Different Shading Methods for Greenhouses in Arid Regions

Abstract

Shading greenhouses in a hot and sunny climate is essential to reduce the inside greenhouse air temperature. However, the type and location of nets need to be addressed properly to determine the shading method that provides a better cooling effect on the greenhouse air. This study was conducted to evaluate the effects of five different shading methods on greenhouse microclimates, and to investigate the cooling potential of each method. Four greenhouse models covered with 200-µm thick plastic film were used for the study: one was kept as control (C), one was whitened with slaked lime (L), and two were shaded with white and black nets (50% shading factor) deployed simultaneously at two locations, in contact (WC, BC) and at 20-cm distance from the cladding film (WD, BD). The microclimatic parameters were measured inside and outside the greenhouse models, and the cooling potential (CP) was predicted for each shading method. The results showed that the black net at 20-cm distance (BD) is desirable as it provides high CP with a reasonable solar radiation transmission. The maximum CP was estimated as 8.5 • C, 8 • C, 6 • C, 3.2 • C, and 2.1 • C for L, BD, BC, WD, and WC, respectively. Shading with white nets is not recommended because their cooling potential is very low. Based on these results, we developed correlations for predicting the CP for each shading method as a function of the transmitted solar radiation flux (S i ). These correlations depend on S i . Accordingly, they can be used for small greenhouses, whitewashed with a slaked lime of any concentration, or shaded with a black net having any shading factor.

Growth and Physiological Characteristics of Strawberry Plants Cultivated under Greenhouse-Integrated Semi-Transparent Photovoltaics

“…Aside from conventional greenhouse shading solutions such as plastic nets [ 14 , 15 , 16 , 17 ] and screens [ 18 , 19 ], one approach that has seen significant expansion and application in recent years is the installation of photovoltaic modules on the greenhouse’s roof. Solar radiation is the most important parameter in satisfying production performance because photosynthesis is a biological process that significantly depends on sunlight.…”

Effect of Sky Discretization for Shading Device Calculation on Building Energy Performance Simulations

“…lead to energy savings greater than 75% in lightning and 20% in air conditioning, respectively. Furthermore, a cooling potential of up to 8.5 • C has been estimated by using appropriate shading methods in arid climates [6]. In addition to energy savings, some authors have also focused their attention on the improvement in comfort conditions.…”