Heliostats daylighting system for multi-floor buildings

Abstract

Daylighting has been considered as a major part of sustainable buildings for saving electric lighting and providing benefits such as, health, visual comfort, and productivity of the occupants. A daylighting system enables the sunlight to capture and deliver it in the interior spaces that cannot be illuminated through windows. Previously, small-scale daylighting systems have been presented using active and passive techniques. This paper presents a daylighting scheme to illuminate the interior of a multi-floor building. Traditional light pipe-based systems are lacked to achieve a high concentration of sunlight for illuminating the interior of a multi-floor building. Here, a highly concentrated light pipe-based daylighting system is presented using heliostats. The daylighting system includes heliostats, light pipe, and light guide to collect, transmit, and distribute the light in the interior of the multi-floor building, respectively. The light guide is made of a reflective film and a prismatic optical film for distributing the light in the interior. Heliostats track the sun and reflect the light towards a circular flat mirror, which inserts the light into the light pipe. To transmit a portion of the light into the light guide for illuminating the interior of each floor, a redirecting mirror is placed at the inlet of the light guide inside the light pipe. Simulation results have shown that an efficiency of 40% is achieved providing almost uniform illumination in the interior.