Influence of Canting Mechanism and Facet Profile on Heliostat Field Performance

The reflective surface profile of a heliostat dictates the flux distribution at the receiver aperture. Reducing size of a heliostat image has been shown to result in performance benefits; however, reducing image area is nontrivial. Aberrations result in image spread of which the dominant aberration is astigmatism. This study investigates the effect of profile variation, in the form of the facets profiles and canting strategy, on astigmatism. In this work an analytical investigation into heliostat imaging is conducted using the Igel and Hughes approach which is incorporated into the HFCAL model to allow annual intercept calculations. The model presents an inexpensive analytical alternative to the existing ray tracing models. The main conclusions are that through the selection of appropriate canting strategies and facet profiles astigmatism can be reduced. The extent to which astigmatic correction is possible with static profiles are dependent on the variation of the incidence angle and the optical alignment angle.