Enhancing the performance of a passive tubular daylighting device using a parabolic-profile collector

Abstract

With the rise of renewable energy systems, there is an increased demand for improved designs of daylighting devices that work without any external energy source to illuminate the deep dark spaces of buildings. Most of the present designs deliver only low light levels especially during the early morning and late evening. This paper focuses on the performance evaluation of specifically designed parabolic-profile collector that redirects the low altitude incident rays of the sun efficiently into a mirror light pipe and thus enhances the lighting to desired levels in the building. Numerical analyses of the same were carried out for the summer solstice, winter solstice, and the autumn equinox for clear sky conditions. Experimental results for the proposed design validated the enhancement in light levels during low altitude sun and controlled lighting during the mid-day sun. The average lighting value obtained through the configured collector during low altitude sun was more than twice the lighting value achieved by a conventional daylight-collecting dome and was ∼20% higher than a prismatic collector.