Pushing the limits of beam-steering lens arrays

Abstract

An essential part of a concentrated solar power system is the solar tracker. Tracking is usually implemented by rotating the entire optical system to follow the sun, adding to the bulk and complexity of the system. Beam-steering lens arrays, on the other hand, enable solar tracking using millimeter-scale relative translation between a set of lens arrays stacked in an afocal configuration. We present an approach for designing and comparing beam-steering lens arrays based on multi-objective optimization, where the objective is to maximize efficiency, minimize divergence, and minimize cost/complexity. We then use this approach to develop new configurations with improved performance compared to previously reported results. As an example of a design suitable for high-concentration applications, we present a system consisting of four single-sided lens arrays that can track the sun with a yearly average efficiency of 74.4% into an exit-cone with divergence half-angle less than ±1◦. We also present a simplified system consisting of three single-sided lens arrays, which can be implemented with less mechanical complexity and potentially lower cost. This simplified system achieves 74.6% efficiency and a divergence half-angle of less than ±2.2◦, and might be relevant for low or medium concentration applications. We believe that these results demonstrate the previously untapped potential of beam-steering lens arrays. If such designs are successfully manufactured, they may become an attractive alternative to conventional external solar trackers for a range of solar energy applications.