A new strategy for improved spectral performance in solar power plants

One method of achieving improved electrical conversion efficiencies in solar power plants is to employ a spectrally selective filter that splits the collected beam into optimised components for two or more spectral receivers. The added cost of supplementary optics and receivers can only be justified if the filter has high performance in operation. The design and manufacture of broadband, low-loss filters however, face several challenges. One of these is the wide range of incidence angles at which the collected beam hits the beam splitter, as the performance of common filters degrades when the incidence angle deviates from the design angle. Dish receivers and micro-tracking Fresnel concentrators, such as the heliostat field in a central receiver design, may provide a fixed distribution of incidence angles across the receiver surface so that the filter can be spatially optimised for a defined angular and energy flux distribution pattern. This paper will discuss the theory and application of such a strategy based on flux mappings produced by raytracing methods for a Multi Tower Solar Array central receiver system planned for construction in Newcastle, Australia.