Daylight autonomy improvement in buildings at high latitudes using horizontal light pipes and light-deflecting panels

Horizontal light pipes (HLP) have shown the potential to convey daylight deeper into buildings. The wide variation in incident angles of sunlight rays and the resulting numerous interreflections of light rays within the pipe are the main reasons for the limited light transmittance of such light pipes during certain daylight periods. This paper presents a research study on different configurations of acrylic laser-cut panels (LCP) applied at the entrance of horizontal pipes as light collectors to increase the transmittance of HLPs and improve daylight autonomy in spaces equipped with HLPs. This study required the development of a suitable methodology. The study begins with an experimental laboratory test of a HLP scale model to determine the light transmittance efficiency (standard daylight guide characteristic) of HLPs with several LCP configurations. The results from the laboratory test are combined with the statistical data for both the direct and diffuse illuminance on the vertical south oriented surface (Satel-Light database) for the location selected for the analyses (Oslo, Norway). The analyses are discussed via the application of a theoretical model of an office space equipped with a HPL as well as through the concept of daylight autonomy (DA) in an indoor space. The paper shows that a certain static LCP configuration has the potential to increase DA100 and DA300 to 10% and 19%, respectively, at a 2.1 m distance from the facade, and 8.75% and 16%, respectively, at a 4.5 m distance. This paper also contributes to lighting science with its data on the light transmittance efficiency of each LCP configuration, which can be applicable in further research.