Optical analysis of Fresnel lens for concentrating PV system

Concentrating PV systems usually use Fresnel lens as radiation concentrator. In this paper, in order to study the concentrating performance of the Fresnel lens, modular Fresnel lens mode was developed and its optical performance was analyzed by the ray tracing method. The imaging characteristic of Fresnel was studied and the optimal imaging location and the size of dispersion spot with different inlet angle were figured out. Flux distribution of the different imaging plane were also examined and compared. The results show that the dispersion spot deviates from the focus and the size of the dispersion spot is enlarged as the incidence angle increase, especially at the high geometric concentration ratio. Then in order to solve the problem, a flat light pipe was applied to reflect sun light onto the absorber plane. The simulation results show that with the new design, sun lights with large inlet angle could also be casted on the absorber.