Reflective secondary optical elements for fresnel lens based concentrator modules

Abstract

AbstractThis paper reports on the development of secondary optics for concentrator photovoltaic (CPV) modules. It focuses on reflective secondary optics designed for high concentration modules using fresnel lenses as the primary concentrating optics. The development of the secondary optics was guided by the idea of designing an optical element suitable for cost effective mass production. The primary concentrating optics of a CPV module can direct only a limited part of the solar aureole (the immediate surroundings of the sun) onto the solar cell. The same applies to light impinging non‐perpendicular to the optical axis of the module (e.g., due to misalignment of the module). Therefore, one of the main functions of reflective secondary optics is to redirect light onto the solar cell that would otherwise not reach it. In order to analyze the performance of secondary optical elements (“secondaries”), a measurement setup is introduced that measures the angular photocurrent response of a CPV device with highly parallel light. This response is referred to as the “angular acceptance function” (AAF). The AAF is used to estimate the performance of the CPV device under various conditions with differing circumsolar radiation (CSR). A CPV test module was manufactured featuring III–V triple‐junction solar cells, a fresnel lens panel as the primary concentrator optic, and the newly developed reflective secondary. The results of a 6‐month outdoor measurement period are presented and compared to the performance of a reference module as well as to the results of the indoor AAF measurements. Copyright © 2011 John Wiley & Sons, Ltd.