Modelling solar flux distributions for fresnel lens CPV systems

A computer model for the simulation of solar flux distribution in the direct and circumsolar regions of the beam irradiation has been created. The model incorporates previous research into circumsolar ratios (CSRs) [1,2]. It is used to demonstrate the importance of realistic solar flux distributions as source inputs in Concentrator Photovoltaic (CPV) simulations. It is shown that the distribution of flux for different circumsolar ratios varies significantly. Such variation will have a considerable effect on the optical image formed at the receiver of a solar concentration system and thus is a necessary consideration in CPV modelling. Flux distributions incident on lenses of various entry apertures are generated and used to investigate the losses in incident flux resulting from tracking errors and CSR variation. It is found that, for a concentrating system with an entry aperture of 0.25°, a 20% loss of net annual incident energy is found with a tracking error of ~0.1°. The same loss is found with tracking errors of ~0.3°, 0.6° and 0.85° with apertures of 0.5°, 0.75° and 1°, respectively.