OPTICS OF PARABOLIC-TROUGH, SOLAR-ENERGY COLLECTORS, POSSESSING SMALL CONCENTRATION RATIOS

A detailed optical analysis of parabolic-trough, solar-energy collectors, obtained by a ray-tracing technique, is presented. The fraction of the diffuse insolation that can be exploited by this type of concentrating collectors has been determined. This fraction is significant for concentration ratios less than 10. The following effects on the collector performance of varying the following parameters were considered: (1) the angular distribution of the diffuse insolation, (2) the scattering of the direct insolation by a transparent aperture cover, and (3) the total optical error of the concentrating system. The acceptance angle and the exploitable part of the diffuse insolation for a generalized parabolic-trough collector have been compared with those for a generalized compound parabolic concentrating collector. It has been demonstrated that the latter exhibits a superior optical behavior with respect to those two factors.