Secondary focusable and uniform convergence microprism in concentrating photovoltaic module

Abstract

Low tracking accuracy of trackers, structure vibration by winds, and lens deformation by temperature lead to non-vertical incident irradiation of Fresnel lens, which necessitates a secondary concentrator in actual engineering application of concentrating photovoltaic module. In this study, a secondary focusable and uniform convergence microprism is added between Fresnel lens and solar cell to improve concentrating efficiency and focal spot energy uniformity. The 3D model of microprism is established by SolidWorks, and important parameters are optimized using Zemax. Results showed that combination of Fresnel lens and focusable and uniform convergence microprism achieves the highest power when upper spherical diameter of secondary microprism measures 18 mm, included angle in opposite side facets equals 116°, spherical height removed from the top is 0.1 mm, and side length of bottom reaches 2.15 mm. The highest power of solar cell surface can reach 2.4932 W, representing a 32.9% improvement; focal spot energy uniformity is 0.71; and module height with secondary microprism measures 88 mm, which reduces by 5.5 mm without secondary microprism. Experimental results show that concentrating static test generation efficiency of a 400-times concentrating module system reaches 34.9%, acceptance angle measures ±1.18°, efficiency loss of module is less than 1.23% when temperature changes from −20°C to 20°C and from 20°C to 50°C, and 400-times module maximum output power totals 142.3 W.