Videographic and photogrammetric characterisations of reflective trough solar concentrators

Abstract
A series of reflective troughs have been designed at the Centre for Sustainable Energy Systems at the ANU that use a hot-sagged glass-laminated-to-glass technique. The troughs are designed with a 2.0 m length and a 1.2 m aperture width, and have a 45° edge angle, and have a 0.72 m focal length. Videographic focal region characterisation of one of the troughs has been undertaken, and preliminary assessments indicate that the concentrator has an effective focal line width of 54 mm over a 1.8 m length, containing 91% of the intercepted radiation. Average concentration ratio over the 54 mm width has been measured at 22 suns. The focal region flux distribution shows some significant 'bands' of concentration, and indicates the more varied nature of focal light distributions that can occur with the more 'distributed' focal line fluxes, as compared with the more uniformly Gaussian distributions that are often apparent in point focus concentrators. Preliminary surface characterisation studies of the trough using close-range photogrammetry have also been undertaken, with computer based ray tracing applied to the measured surface to produced predicted flux distributions that closely approximate the videographically measured distributions. The photogrammetrically measured surface displacements across the trough indicate that a large proportion of the non-uniformities arise from deviations occurring at the lateral edges of the trough. This highlights a need to improve the fabrication methodology for the troughs in this area.