Simple Köhler homogenizers for image-forming solar concentrators

Image-forming solar concentrators which project an image of the sun on the photovoltaic cell may have high thermodynamic efficiency, but suffer from non-uniform irradiance distribution and a nonsquare irradiance pattern. In this paper we discuss how to apply the Köhler illumination technique to solve these problems with an optimization approach. Two examples, a Fresnel lens-based concentrator and a two-mirror aplanatic system, are shown for demonstration. The uniformity of these systems is greatly improved by adding simple Köhler homogenizers in the form of aspheric lenses generated with our approach.