Model construction and optical performance research of a novel double-involute compound parabolic collector with evacuated tube to eliminate ray escape

To eliminate ray escape at the bottom of standard compound parabolic collector (S-CPC) with an evacuated tube receiver, a novel double-involute CPC (DI-CPC) was proposed. The ray-tracing model for the CPC with evacuated tube, established on geometric optics reflection principles, underwent experimental validation of its accuracy. Within the ray-tracing model, the spectral reflectivity of the silver-plated mirror surface, transmissivity through the glass tube, and coating absorptivity were expressed as functions of incident angles, thereby rejecting constant-value assumptions. Ray escape at the bottom was effectively eliminated through the structural improvement of the DI-CPC. The DI-CPC exhibited a 15.2 % enhancement in optical efficiency at 0° incident angle. The ray escape above absorber after the structure improvement can be eliminated by increasing the absorber radius or using single-axis azimuthal tracking method. With an absorber radius of 25.6 mm, the average optical efficiency of DI-CPCR exhibits an 8.97 % enhancement over S-CPC. Under the single-axis azimuthal tracking mode with twice-daily adjustment, the diurnal average values of optical efficiency of the S-CPC, DI-CPC and DI-CPCR were 62.4 %, 72.4 %, and 73.1 % respectively on the summer solstice, and were 61.9 %, 72.1 %, and 73.0 % respectively on the winter solstice.