Potential gain through implementation of astigmatic corrected heliostats

Heliostats in a central receiver system (CRS) field used for concentrated solar power (CSP) experience a range of incidence angles during operation. The thus incurring astigmatism inflicts optical losses and reduces solar concentration through enlarging the focal spot at the receiver. A heliostat can theoretically be continuously astigmatism free if the shape of the concentrator/reflector is continuously adapted to the occurring incidence angle. In order to show the potential optical benefits of such an implementation, raytracing simulations were performed with models using both conventional and astigmatic-corrected heliostats. We show that the implementation of the astigmatic corrected heliostat allows a reduction in receiver aperture at equal optical yield as compared to conventional heliostats (heliostats with constant focus), and which heliostats in a field are affected most by astigmatism.