The impact of changing solar screen rotation angle and its opening aspect ratios on Daylight Availability in residential desert buildings
KAUST Grant NumberC0015
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AbstractIn desert sunny clear-sky regions solar penetration can become excessive. This can cause non-uniform daylight distribution, glare and high solar heat gain, affecting both visual and thermal comfort. Shading devices, such as solar screens, were usually used to diffuse and prevent direct solar penetration into spaces. This paper investigates the impact of changing solar screen axial rotation angle and screen opening aspect ratio on daylighting performance in a typical residential living room space under the desert sunny clear-sky. The larger aim is to arrive at efficient solar screen designs that suit the different orientations.The study was divided into three consecutive phases. In phase one, the effect of the two parameters on Daylight Availability was tested. The solar screen was axially rotated by three different angles at 10° increments. Also, the aspect ratio of the screen opening in both horizontal and vertical directions was changed systematically. Simulation was conducted using the annual Daylight Dynamic Performance Metrics (DDPMs). In phase two, the Annual Daylight Glare Probability (DGP) metric was evaluated for the cases that were found adequate in phase one. In the third phase, the annual solar energy transmittance through the screen was calculated for the cases that achieved acceptable performance in the two previous phases in order to identify the more energy efficient screens.Solar screens with openings having horizontal aspect ratios were found to be the most effective, while those with vertical aspect ratios were achieved the lowest performance. In the North orientation, since almost all the cases that were tested in this research provided acceptable daylighting performance, the designer now have a variety of options to choose from. Preference should be given to screen openings of horizontal aspect ratios, especially the 12:1 and 18:1 (H:V) screens that achieved the best performance where 92% of the space was " daylit" in comparison with only 53% of the base case. In the East orientation, it is advisable to use the 12:1 (H:V) screen opening ratio, as it was found acceptable in the two daylighting testing phases and achieved the best performance in regards to annual transmittance of solar radiation. For the South orientation, there were also many acceptable choices. However, the 3:1 screen aspect ratio is recommended as it assists in saving energy by reducing the annual transmitted solar radiation (60% reduction) while achieving acceptable daylighting performance. © 2012 Elsevier Ltd.
CitationSherif AH, Sabry HM, Gadelhak MI (2012) The impact of changing solar screen rotation angle and its opening aspect ratios on Daylight Availability in residential desert buildings. Solar Energy 86: 3353–3363. Available: http://dx.doi.org/10.1016/j.solener.2012.09.006.
SponsorsThis publication is based on work supported by Award No. C0015, made by King Abdullah University of Science and Technology (KAUST).