Design of Primary Optical Element with Multiple Sublenses to Improve Irradiance Uniformity over the Receiver of Concentrator Photovoltaic System

Abstract

In this study, a primary optical element (POE) was designed to collect and distribute solar radiation uniformly on a multijunction solar cell in a concentrator photovoltaic (CPV) system. The POE combined multiple free-form sublenses to improve the uniformity of the concentrated sunlight and reduce the optical losses. Each sublens was designed based on the principles of nonimaging optics such as the edge ray theorem, Snell’s law, and the conservation of optical path length. Furthermore, the POE had multifocal points for focusing the direct sunlight, in which the number of focal points equaled the number of the sublenses. Each free-form sublens can guide and distribute the direct sunlight uniformly over the receiver; thus, the uniformity of concentrated light over the multijunction solar cell was improved significantly. The simulation results showed that the designed POE can concentrate the direct sunlight on a square area that matched the active site of the multijunction solar cell with a concentration ratio of about 484 times, uniformity of about 78%, and total optical losses smaller than 20%.