A novel square Fresnel lens is described which illuminates a circular solar cell. The square lens can be close-packed in a large photovoltaic array to help minimize system cost. The novel design is accomplished by forming the Fresnel facets in the corners of the lens with different focal lengths than the central portion of the lens. Acrylic lenses were compression molded from a master cut according to the design and were determined to be 79.4% efficient in the solar cell spectral response range.
E. L. Burgess,
D. L. Marchi,
"A Novel Square Fresnel Lens Design for Illuminating Circular Solar Cells," Optical Engineering 17(3), 173299 (1 June 1978). https://doi.org/10.1117/12.7972232