Optical Design of a Novel Two-Stage Solar Trough Concentrator Based on Pneumatic Polymeric Structures

An innovative concept for fabricating solar trough concentrators based on pneumatic polymer mirrors supported on precast concrete frames is presented. Optical aberration is corrected by means of a secondary specular reflector in tandem with a primary cylindrical concentrator. The optimal design is formulated for maximum solar flux concentration. The Monte Carlo ray-tracing technique is applied to determine the effect of reflective surface errors and structural beam deformations on the performance of the combined primary and secondary concentrating system. The numerical results are validated with field measurements on a 49.4 m length, 7.9 m width sun-tracking prototype system. Theoretical maximum solar concentration ratio is 151 suns; the measured one with a flat secondary reflector was 55 suns.