High Acceptance Angle Optical Fiber Based Daylighting System Using Two-stage Reflective Non-imaging Dish Concentrator

It has been observed that lighting systems consume a significant amount of energy in high-rise buildings even during the daytime. To save power consumption and improve indoor environments, daylighting can be implemented for the interior of buildings by guiding sunlight via optical fibers. In this paper, we propose a new two-stage reflective non-imaging dish concentrator (NIDC) consisted of reflective primary and secondary mirrors that focus sunlight onto high acceptance angle optical fibers located at the target of the concentrator. The optical fibers can guide the concentrated sunlight into the interior area of the building. The new concentrating type of daylighting system was designed, fabricated and evaluated. Under normal sunny day condition with solar irradiance of 1000 W/m2, the calculated average illuminance for our prototype daylighting system with a reflective area of 0.2 m2 is 647.94 lux to illuminate an office area of 6.3 m2, which is also equivalent to illuminate a bigger area of 8.164 m2 based on standard average illumination of 500 lux.