Test of a “trumpet” secondary concentrator with a paraboloidal dish primary

Abstract Secondary concentrators properly designed according to the principles of nonimaging optics can increase the achievable concentration ratio of a point focus solar concentrator substantially above the level for a focussing primary alone. One such secondary is the so called “trumpet” concentrator whose hyperbolic shape is derived from the theory of the geometrical vector flux. A practical version was designed, fabricated and tested recently on the large 11-meter Paraboloidal Test Bed Concentrator operated by the Jet Propulsion Laboratory. The secondary concentration ratio was 2.1 x . That is, it reconcentrated the energy in a focal spot of 20.3 cm diameter into a circle of 14.0 cm diameter corresponding to an area reduction of 2.1 to 1. The trumpet performed as predicted by optical models. When operating with a receiver corresponding to a gross geometrical concentration ratio of 4800:1, addition of the trumpet increased the intercepted energy by 30%. Characterized in another way the trumpet increased the geometric concentration ratio from 2200:1 for the primary alone to nearly 4800:1 with an efficiency of >96%. The results of the test demonstrate that with a properly cooled secondary one can either improve the achievable concentration ratio or relax the primary tolerance requirements for essentially negligible increase in system cost or complexity.