The use of anidolic lighting system in improving daylight illuminance of high-rise buildings in Hong Kong

Abstract

This paper describes the application of advanced daylighting system to improve daylight illuminance of residential units in Hong Kong as one of the most dense cities. In the high-dense environments, residential units that located at lower floor level are very difficult to get daylight because most parts of the sky are blocked by surrounding buildings. The only daylight available is coming from the zenith parts of the sky and reflected from surrounding buildings. Light coming from the zenith has very little contribution to the illuminance of room that only depend on side opening. In order to make use of this light, light redirecting device should be used. There are some light redirecting devices available; however, most of them only work well for direct light. Because Hong Kong condition dominated by overcast sky and most of light is diffuse light. The system selected shall be able to works well for diffuse light. One of these systems is anidolic lighting device. This device collects light from the zenith and redirects it to the rooms by using parabolic concentrator. The results show that a significant improvement of daylight illuminance can be achieved at lower floor level. There were improvement of 63.6% and 12.1% of DF and DA, respectively, by using the anidolic (Case 2) at the working plane of 80 cm. Case 2 also performed well in the vertical illuminance evaluation, by improving the brightness of the wall in the rear parts. Therefore, using anidolic daylighting system would improve the daylight performance of lower floor of the high-rise residential buildings in high-dense situation. This system can be applied for the refurbishment of the existing residential buildings that experience very low daylight illuminance as well as new buildings.