High-concentration freeform microtracking concentrators with single-axis external tracking

Abstract

Microtracking concentrators enable the use of concentrator photovoltaics without the need for accurate two-axis external solar tracking. However, the wide tracking range required from stationary microtracking concentrators leads to designs with reduced concentration or complex designs with multiple moving surfaces. Additionally, stationary microtracking concentrators suffer from high cosine projection losses. We propose combining microtracking concentrators with low-precision horizontal single-axis trackers commonly used for conventional silicon photovoltaics. This reduces the demands of the microtracking concentrator while simultaneously reducing the cosine projection losses. We show how the performance in such a configuration can be boosted using a combination of freeform surfaces and a modified lenslet packing scheme and present a concentrator achieving 85% average yearly efficiency at a geometric concentration of 776x.