Aplanatic optics for solar concentration

Aplanats are imaging optics that completely eliminate both spherical aberration and coma. They can fulfill the practical virtues of permitting sizable gaps between the absorber and the optic, as well as compactness. However, the ability of aplanats to efficiently approach the thermodynamic limit to flux concentration and optical tolerance had remained unrecognized. Both fundamental and applied aspects of dual-mirror aplanats are reviewed and elaborated, motivated by the exigencies of tenable, maximum-performance solar concentrators, including examples from commercial concentrator photovoltaics (CPV). Promising designs for future photovoltaic concentrators are also identified, illustrating how pragmatic constraints translate into devising fundamentally new optics.