Concentrating behavior of elastic fresnel lens solar concentrator in tensile deformation caused zoom

The focal length of the Fresnel lens changing with the light incident angle will decrease Fresnel lens solar concentrators' energy efficiency and daily working hours, which seriously hinders its commercial application. Existing solutions, mainly including single-axis tracking, two-dimensional tracking, and passive tracking have their limitations and fail to realize the maximum application potential of the Fresnel lens. This paper proposes a novel elastic Fresnel lens solar concentrator, whose focal length can be regulated by tensile deformation. The mechanical and optical coupling simulations are conducted to reveal its concentrating behavior during tensile deformation. An exemplary elastic Fresnel lens with an aperture width of 200 mm and an original focal length of 360 mm is designed and studied. The simulation results illustrate that the optimal base thickness of the elastic Fresnel lens is 1 mm when its prism thickness is 2 mm. Under the optimal thickness parameters combination, the elastic Fresnel lens has an effective elongation rate r about 15%, which increases the focal length by 163 mm and 47% to the original focal length. The focus width only increases from 16 mm to about 20 mm when adjusting the focal length from 360 mm to 523 mm. Besides, the step-zoom strategy increases the exemplified elastic Fresnel lens' acceptable angle from 30 degrees to 45 degrees. The tensile deformation caused zoom method increases the working hours of Fresnel lens by 1.5 times, demonstrating the effectiveness of this method.