External perforated Solar Screens for daylighting in residential desert buildings: Identification of minimum perforation percentages
External perforated Solar Screens for daylighting in residential desert buildings: Identification of minimum perforation percentages
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DOI：
10.1016/j.solener.2012.02.029
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发表时间：
2012-06
期刊：
影响因子：
6.7
通讯作者：
A. Sherif;Hanan Sabry;T. Rakha
中科院分区：
文献类型：
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作者：
A. Sherif;Hanan Sabry;T. Rakha
沙漠气候是由晴朗的天空条件赋予的，为自然光在采光建筑室内空间的最佳利用提供了极好的机会。然而，在埃及和沙特阿拉伯等国家，沙漠天空的阳光充足的条件导致直接太阳辐射的进入，这导致热不适和不期望的眩光的发生。一种用于允许日光同时控制太阳能渗透的遮阳系统是“太阳能屏幕”。很少有研究工作涉及外部太阳能屏幕的不同设计方面及其对采光性能的影响，特别是在沙漠条件下，尽管这些屏幕在历史上证明了它们在传统建筑中控制太阳辐射的有效性。本文报道了一项调查的结果，该调查研究了太阳能屏幕的穿孔百分比对沙漠地区建筑物的典型住宅起居室采光性能的影响。目的是确定在特定设计情况下和全年提供足够照度水平的筛网开口的最小穿孔百分比。研究工作分为三个阶段。第一阶段侧重于分析特定日期和时间的日光照明照度水平，而第二阶段则建立在第一阶段的结果基础上，并使用动态日光性能测试（DDPM）来解决全年性能问题。第三阶段讨论了在特定情况下眩光入射的可能性，在第一阶段的分析过程中，在某些特定点发现照度水平非常高。该研究考察了室内空间的采光性能，并选择了一些假设的固定实验参数来代表位于沙漠环境设置中的典型住宅起居室的主要特征。第一阶段的实验表明，屏幕满足大多数测试用例的要求。照明水平在检查的住宅空间是令人满意的近区的情况下，83%，在中长区的53%，而远区套房的情况下，40%。屏幕对采光的影响被认为是非常依赖于窗口的方向和一天中的时间。在第二阶段，年“日光利用率”的百分比与屏幕穿孔百分比密切相关。随着穿孔百分比的降低，采光和过光空间的百分比降低。与此同时，部分采光面积的空间增加了类似的百分比，无论方向。作为两个研究阶段的结果，建议对与南方向测试情况类似的空间使用至少80%的穿孔百分比。在第三阶段，初步调查表明，使用屏幕可以显着减少眩光现象的发生。此外，建议研究设计具有非均匀穿孔比的太阳能屏幕的效率。这些措施可有助改善不满意个案的中长及远区的照度水平。最后，太阳能屏幕的最小穿孔百分比是针对特定的设计案例提出的，这些案例包括不同的方向，季节和一天中的时间。此外，还提供了一个工具，建筑师可以使用该工具根据所需的年度“日光”面积设计太阳能屏幕，有效地实现功能需求。
The desert climate is endowed by clear sky conditions, providing an excellent opportunity for optimum utilization of natural light in daylighting building indoor spaces. However, the sunny conditions of the desert skies, in countries like Egypt and Saudi Arabia, result in the admittance of direct solar radiation, which leads to thermal discomfort and the incidence of undesired glare. One type of shading systems that is used to permit daylight while controlling solar penetration is “Solar Screens”. Very little research work addressed different design aspects of external Solar Screens and their influence on daylighting performance, especially in desert conditions, although these screens proved their effectiveness in controlling solar radiation in traditional buildings throughout history. This paper reports on the outcomes of an investigation that studied the influence of perforation percentage of Solar Screens on daylighting performance in a typical residential living room of a building in a desert location. The objective was to identify minimum perforation percentage of screen openings that provides adequate illuminance levels in design-specific cases and all-year-round. Research work was divided into three stages. Stage one focused on the analysis of daylighting illuminance levels in specific dates and times, while the second stage was built on the results of the first stage, and addressed year round performance using Dynamic Daylight Performance Metrics (DDPMs). The third stage addressed the possibility of incidence of glare in specific cases where illuminance levels where found very high in some specific points during the analysis of first stage. The research examined the daylighting performance in an indoor space with a number of assumed fixed experimentation parameters that were chosen to represent the principal features of a typical residential living room located in a desert environment setting. Stage one experiments demonstrated that the screens fulfilled the requirements of the majority of tested cases. Illuminance levels in the examined residential space were satisfactory in 83% of the near zone cases and 53% in the mid-length zone, while the far zone suites 40% of the cases. Screen influence on daylighting was found to be very much dependent on the orientation of the window and time of the day. In stage two, the percentage of annual “Daylight Availability” was very much related to screen perforation percentage. As perforation percentage decreased, the percentage of Daylit and Over lit spaces decreased. At the same time, Partially Daylit areas of the space increased with similar percentages irrespective of the orientation. As a result of the twofold research stages, it is recommended to utilize a minimum of 80% perforation percentages for spaces similar to the tested case in the South orientation. In stage three, an initial investigation suggests that the use of screens can significantly reduce the occurrence of glare phenomena. Also, it is suggested to study the efficiency of designing Solar Screens that have non-uniform perforation ratios. These could prove useful in improving the illuminance levels in the mid-length and far zones of the unsatisfactory cases. In conclusion, minimum perforation percentages for Solar Screens were presented for specific design cases that encompassed different orientations, seasons and time of the day. In addition, a tool that could be used by architects for based on required annual “Daylit” areas for the design of Solar Screens that effectively achieve functional needs was provided.