Optical performance of CPCs suitable for all-glass evacuated tubes

The angular dependence of optical efficiency of six compound parabolic concentrator (CPCs) suitable for concentrating radiation on all-glass evacuated tubes is investigated by ray-tracing method, and the annual radiation concentrating on unit length of solar tubes by means of six CPCs is estimated based on the angular dependence of optical efficiency of CPCs and solar geometry. Results show that the optical efficiency of CPC designed by “hat-shaped” absorber with a V-groove at the bottom of reflectors is higher than that of other CPCs for the case of the incidence solar rays within the acceptance angle of full CPC, otherwise less than that of other CPCs. It is concluded that the CPC designed by “ice-cream shaped” absorber is the optimal design, and the one designed by the cover tube is the most inferior solution in terms of the annual radiation concentration on the solar tube.