Interception on Solar Absorbers: Ray Tracing for Comparison between a Parabolic Reflector and a Compound Parabolic Concentrator
Abstract
A Compound Parabolic Concentrator (CPC) can direct incoming rays on an upper aperture to pass through a lower smaller aperture. The case for consideration here is for an absorber to be positioned inside the CPC, where a heat transfer fluid will circulate for heat absorption and further transport to a heat storage. Continuous solar tracking is to be avoided but tilting the concentrator 2-3 times during a day can be accepted. A 3D CPC is compared with a normal Parabolic Reflector (PR) for similar concentration ratios. The comparison is made using ray tracing, where the sun angle is scanned over the acceptance angles and the interceptions on a cylindrical absorber are compared between the two systems. For low concentration ratios, the performances of the two reflectors are comparable, with about 10% improvements in interception ratios with the CPC over the PR. The concentration ratios for a CPC are limited. For the PR an optimum can be considered, between increasing the concentration ratio but at the cost of decreasing the interception ratios. Keywords: Compound Parabolic Reflector, ray tracing, optical efficiency, concentrating solar thermal, solar heat absorber