Design Of Fresnel Concentrating Optical System With High Homogeneity Of Energy Distribution

Solar energy is the most potential energy in the21st century. As one of the most effective technology, CPV system has become a hot subject around the world. But there still present a lot of issues about CPV, such as non uniform distribution of energy which give rise to hot-spots in the plane of solar cell and decrease the service life of the cell; Acceptance angle is small and it can’t match with the tracker precisely; These issues will lead to lower efficiency in the photovoltaic system. In order to improve uniformity of energy and increase acceptance angle, paper designed a concentrating optical system. It consists of the main condenser-the ring-shaped-focus Fresnel and the secondary condenser-the total reflected optical funnel. Two kind condensers are deeply researched and the complete theory models have been established respectively.First, studied the principle of ring-shaped-focus Fresnel and gave design formulas. Results show that:Each ring depth of the ring-shaped-focus Fresnel lens is smaller than the common Fresnel; Ring-shaped-focus Fresnel has a higher optical efficiency and spot uniformity; Spot uniformity decreases as the condenser caliber increases; Spot uniformity decreases as Cg increases; Spot uniformity and optical efficiency of the Fresnel condenser is gradually decreases as acceptance angle increases.Second, using edge ray principle and law of reflection to design total reflected optical funnel and derived design formulas. Results show that:Spot uniformity and length increases as edge light reflects times in the total reflected optical funnel; With acceptance angles increases, the spot uniformity and optical efficiency of converging optical system gradually decreases; Compared to ring-shaped-focus Fresnel, spot uniformity and optical utilization of the converging optical system significantly increased; whether it is in the acceptance angle or optical efficiency, converging optical system has obvious advantages. But length of the optical system increases when adds optical funnel.Finally, optimized structural parameters (R, r, f) of the concentrating optical system. When given R and r, H increases with f increases, at the same time the spot uniformity has remained high, but the optical efficiency has a turning point, so f has been optimized as the value which corresponding to the optical efficiency at the turning point; When given R and f, H increases with r increases, at the same time the optical efficiency has remained high, but spot uniformity has a turning point, so r has been optimized as the value which corresponding to the spot uniformity at the turning point. The concentrating optical system whose R is200mm has been optimized as:r is10mm,f is320mm.Its optical efficiency is86.5%, uniformity is0.862.In short, Paper presented a method of designing and optimizing on converging optical system. It is expected to provide theoretical basis for concentrator photovoltaic systems development and reference for the practical design and product development.