Background

One of the major design goals in tracking solar concentrators is to capture light from a source that is extended in angular extent (the sun subtending approximately half a degree) and perhaps slightly off-axis (a few degrees being typical in solar concentrators intended for concentrator photovoltaic (CPV) applications), and deliver it to an exit aperture such that the exit aperture is uniformly illuminated by the source (Köhler illumination).

It is also desirable to reduce the volume and mass of the concentrator relative to its surface area, meaning that the light concentrating optical elements should be as thin as possible.

Description

A University of California, Merced researcher has developed a novel solar concentrator design involving two layers in the optical element, where the first layer employs a Fresnel-like arrangement of parabolic air gaps to reflect the incident light beam to a greater angle from the central axis as it passes to the second layer, effectively trapping the light within the second layer.The second layer, then, employs a series of internal reflections within the layer to concentrate the light at a central exit aperture. The two layers can be constructed as a single piece of any transparent material, such as glass or acrylic.

Applications

The principal use for non-imaging concentrators is for generating electricity from photovoltaic cells at higher light concentrations (and thus smaller and less costly cells) than is the case without concentrators.

Advantages

This solar concentrator design combines light trapping and total internal reflection for light concentration with radial symmetry and skew invariance of the light pathways. The result: a highly concentrated, uniform illumination of the central exit aperture is achieved. The separation of light trapping and light concentration in two separate layers offers greater control over critical solar concentrator design parameters than other designs.

Patent Status

Patent Pending

Inventor

Roland Winston
Weiya Zhang