A Nonimaging Receiver for Parabolic Trough Concentrating Collectors

The design of a nonimaging secondary reflector as part of a parabolic trough receiver has been developed and evaluated. A detailed optical model was used for evaluation, which offered insight into the optical performance of the secondary and showed that the design offers about a 1% net increase in optical efficiency. In addition, the secondary was estimated to reduce heat loss from a high-performance evacuated receiver by about 4%. Overall, the net performance advantage of the secondary reflector is calculated to be 1.4%, that is, the entire trough collector field would have a 1.4% greater annual thermal energy output. This performance increase is small, but the non-imaging secondary also achieves other indirect benefits such as better flux uniformity around the absorber tube, and increased tolerance of parabolic trough collectors to optical errors.