Efficient sunlight harvesting with combined system of large Fresnel lens segmented mirror reflectors and compound parabolic concentrator without tracking sun for indoor daylight illumination

Abstract

Sunlight is a great substitute for indoor artificial lighting during the daytime but still isn't so viable because of the cost of fiber-based daylighting system and its efficiency. In this paper, we report the design and development of a cost-effective non-mechanical tracking-based solar concentration system using a combination of a large Fresnel lens, segmented mirrors, and segmented compound parabolic concentrator (SCPC) for indoor daylighting application. This system presents the three-stage collection of sunlight by means of extending the collection aperture vertically while keeping the horizontal area same. First one is the concentrated light from the Fresnel lens, the second one is the direct sunlight incident onto the CPC and the third one is the direct sunlight reflected from the segmented mirrors onto the CPC. Hence the light transported through this system is adequate for illumination purposes inside the room. The manufacturing of ideal CPCs through the moulding process is both expensive and complex, and it necessitates extreme precision. Therefore, a cost-effective and efficient segmented CPC is designed and developed using a highly reflecting mirror-polished aluminum sheet which works well compared to the ideal CPC. To transport concentrated sunlight inside the room a highly reflecting horizontal light pipe is designed and developed. The collimated light at the output is challenging therefore, we have coupled inverted CPC at the exit of segmented CPC in the system. Further, to guide sunlight deep into the rooms we have coupled the entire system with a rectangular light pipe. An efficient diffuser is coupled at the end of the rectangular light pipe to illuminate the room uniformly. Various optical parameters such as illuminance, color rendering index (CRI), and correlated color temperature (CCT) values are analyzed from the result obtained which shows that the system can efficiently transport sunlight deep inside the room throughout the day. Therefore, the proposed system is very much helpful for the sustainable development of a country.