Design philosophy and construction of a high concentration compound parabolic concentrator

Abstract

A compound parabolic concentrator (CPC) with a concentration ratio of 16:1 is under development at CSIR for volumetric receiver and solar fuels development. The ideal shape has been approximated by 6 and 12 facets in the longitudinal and circumferential directions respectively. A sandwich construction method has been pursued to achieve the cooling channels: the 2mm mirror panels are bonded to a laser-cut 2mm aluminium heat conduction plate, itself bonded to a 4.5mm aluminium plate into which a serpentine cooling channel has cut by waterjet. A 1mm stainless steel backing plate on the rear surface (itself welded to lasercut stainless steel longitudinal ribs) provides the necessary shape and structural rigidity. The spectral transmission of the 2mm soda lime mirror glass used for the concentrator facets was measured using a uniform light source and an ASD FieldSpec(TM) spectroradiometer. This, together with the SMARTS solar spectrum model, was used in a ray tracing analysis which determined the overall efficiency of the concentrator to be 68.7%. Construction is nearly complete and actual efficiency will be determined using a hemispherical cavity calorimeter.