Transforming the cost of solar-to-electrical energy conversion: Integrating thin-film GaAs solar cells with non-tracking mini-concentrators

Abstract

Practical solar energy solutions must not only reduce the cost of the module, but also address the substantial balance of system costs. Here, we demonstrate a counter-intuitive approach based on gallium arsenide solar cells that can achieve extremely low-cost solar energy conversion with an estimated cost of only 3% that of conventional gallium arsenide solar cells using an accelerated, non-destructive epitaxial lift-off wafer recycling process along with a lightweight, thermoformed plastic, truncated mini-compound parabolic concentrator that avoids the need for active solar tracking. Using solar cell/concentrator assemblies whose orientations are adjusted only a few times per year, the annual energy harvesting is increased by 2.8 times compared with planar solar cells without solar tracking. These results represent a potentially drastic cost reduction in both the module and the balance of system costs compared with heavy, rigid conventional modules and trackers that are subject to wind loading damage and high installation costs. Thin-film GaAs solar cells integrated with wide-acceptance-angle compound parabolic concentrators could slash solar energy costs. Researchers at the University of Michigan in the USA have dramatically reduced the material and fabrication costs of GaAs solar cells by using an accelerated, non-destructive epitaxial lift-off fabrication process and by incorporating mini concentrators. They estimate that the material and fabrication costs of these solar cells are a mere 3% those of analogous substrate-based GaAs cells and 11% those of solar cells produce by conventional epitaxial lift-off methods. The wide acceptance angles of the concentrators means that the solar cell orientation only needs adjusting a few times per year, eliminating the need to use expensive active solar tracking. Furthermore, the solar cells can be operated at or near room temperature, and hence do not require active cooling.