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International Journal of Photoenergy
Volume 2017, Article ID 1945875, 11 pages
Research Article

Optical Tests on a Curve Fresnel Lens as Secondary Optics for Solar Troughs

1CNR-National Institute of Optics (INO), Largo E. Fermi, 6, 50125 Firenze, Italy
2Department DIEF, University of Florence, Via Santa Marta, 3, 50139 Firenze, Italy

Correspondence should be addressed to P. Sansoni; ti.oni@inosnas.aloap

Received 30 May 2017; Accepted 9 July 2017; Published 12 September 2017

Academic Editor: Prakash Basnyat

Copyright © 2017 D. Fontani et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


A curve Fresnel lens is developed as secondary concentrator for solar parabolic troughs to reduce the number of photovoltaic cells. Specific measurements and optical tests are used to evaluate the optical features of manufactured samples. The cylindrical Fresnel lens transforms the focal line, produced by the primary mirror, into a series of focal points. The execution of special laboratory tests on some secondary concentrator samples is discussed in detail, illustrating the methodologies tailored to the specific case. Focusing tests are performed, illuminating different areas of the lens with solar divergence light and acquiring images on the plane of the photocell using a CMOS camera. Concentration measurements are carried out to select the best performing samples of curve Fresnel lens. The insertion of the secondary optics within the concentrating photovoltaic (CPV) trough doubles the solar concentration of the system. The mean concentration ratio is 1.73, 2.13, and 2.09 for the three tested lenses. The concentration ratio of the solar trough is 140 and approaches 300 after the introduction of the secondary lens.