Self-tracking concentrator based on switchable transparency and rejected-ray recycling

We present and analyze a design for a self-tracking solar concentrator based on a switchable-transparency optical element. The switchable element forms a moving aperture that tracks the motion of the sun to admit light into a CPC in which rays are 'recycled,' undergoing many passes through the concentrator to increase the absorption probability. This design has the benefit of not requiring any control of the angular profile of internal radiation, in contrast to other design that rely on total internal reflection to confine and transport the light. Via probabilistic models and rigorous ray tracing, we show that this design can exhibit performance comparable to other self-tracking designs. In particular we demonstrate a system with a 70x geometric concentration ratio and a tracking range of +/-20 degrees, achieving optical efficiencies of up to 65%.