Photogrammetry analysis of a vacuum-membrane solar dish using elliptical television antennas

Abstract

The design of a solar dish usually involves the complex trade-off between cost and optical quality. The use of off-the-shelf elliptical television antennas in a vacuum-membrane solar dish array is investigated in this paper, in an effort to reduce the cost of solar concentration. Each facet comprised a 50-ȝm-thick Mylar sheet membrane, stretched and sealed over the elliptical rim of an off-the-shelf satellite television antenna, forming a narrow cavity in which a vacuum could be drawn to pull the Mylar sheet into a concave shape. The shape of the facet concavity was investigated using photogrammetry. An elliptic paraboloid and a hemi-ellipsoid were fitted to the photogrammetry results, and it was determined that both fits could be used to represent the concave shape. The investigation allowed for the concave shape to be modelled in a ray tracing analysis, where the flux map was compared with the result from a lunar flux mapping analysis. Comparison of the intercept factor trends showed that further investigation into quantifying the contributions of individual facet alignment errors should be performed to further improve the model. With improvements in individual facet alignment, the use of off-the-shelf elliptical television antennas in a vacuum-membrane solar dish array can be a viable solution to reduce the cost of solar concentration.