External perforated window Solar Screens: The effect of screen depth and perforation ratio on energy performance in extreme desert environments

In hot arid desert environments, the solar radiation passing through windows increases the cooling loads and the energy consumption of buildings. Shading of windows can reduce these loads. Unlike the woven solar screens, wooden solar screens have a thickness that provides selective shading properties. Perforated wooden solar screens were traditionally used for windows shading. Developing modern types of these shading systems can lead to significant energy savings.The paper addresses the influence of changing the perforation percentage and depth of these screens on the annual energy loads, hence defining the optimum depth/perforation configurations for various window orientations. Series of experiments were performed using the EnergyPlus simulation software for a typical residential building in the Kharga Oasis, located in the Egyptian desert. A range of perforation percentages and depths were tested.Conclusions prove that external fixed deep perforated solar screens could effectively achieve energy savings up to 30% of the total energy consumption in the West and South orientations. Optimum range of depths and perforation percentages were recommended. These are: 80–90% perforation rate and 1:1 depth/opening width ratio. These lighter and deeper solar screen configurations were found to be more efficient in energy consumption in comparison with the traditional ones.

► Solar Screens achieved energy savings up to 30% in the west and south orientations.
► Recommended screens are of 80–90% perforation rate and 1:1 depth/perforation ratio.
► Solar Screens near optimum range extended from 0.75 to 1.25 depth ratio.
► Energy savings were barely significant in the North orientation.
► Screen depth was found to be an important factor that affects energy savings.