New Vistas in Solar Concentration with Gradient Index Optics.

摘要

Four innovations in the fields of optical design and solar concentration are presented: a) the derivation of fundamentally new gradient-index (GRIN) distributions for perfect optical instruments. For the first time, GRIN lenses for visible and solar radiation with refractive index distributions that are amenable to current fabrication techniques are presented. Those lenses perform at nature's cardinal limits (within the geometrical optics approximation — valid for essentially all solar applications), i.e. perfect imaging and ideal nonimaging performance for monochromatic radiation and unprecedented image fidelity and near-ideal flux concentration for the full solar spectrum. Until now, there have been no GRIN solutions (for performance approaching the fundamental limits of flux concentration and image fidelity) that can accommodate an extended constant-index core — especially relevant because the only available fabrication techniques for visible and solar GRIN lenses require a constant-index core. b) The design, for the first time, of a nominally stationary solar concentrator with attainable geometric concentration of the order of 103 suns with high collection efficiency. The burden of tracking is transferred inside the stationary module where mm-scale motion of GRIN perfect imaging lenses tracks the sun. This creates the possibility for rooftop Concentrator Photovoltaics (CPV) with unprecedented optical performance and exceptional optical tolerance. c) The design of a nominally stationary solar concentrator with a modified Simultaneous Multiple Surface technique for nonimaging contoured lenses with flux concentration of the order of tenths of suns. d) The design of planar GRIN lenses able to deliver flux concentrations close to the thermodynamic limit to Solar Concentration with a single, optical element, previously deemed unattainable and particularly suitable to dual-axis tracking CPV.