Characterization of two secondary optics for a fresnel mirror
Authors: Fontani D., Jafrancesco D., Francini F., Sansoni P.
Autors Affiliation: CNR-INO Istituto Nazionale di Ottica, Largo E. Fermi, 6, Firenze, 50125, Italy
Abstract: The advantage of this laboratory optical characterization is to reproduce under controlled conditions an existing solar plant of Fresnel mirror type. The plant has 20 identical plane mirrors that concentrate the sunlight toward the secondary optics, which focuses it on the receiver. The procedure consists in performing the tests separately simulating the illumination of each plane mirror, finally combining the measured results to obtain collection efficiency and concentration factor of the entire solar plant. Two alternative secondary optics, a prismatic lens and a reflective concentrator, were optically tested to compare their behaviour. The total collection efficiency is similar, while the concentration factor is higher for the prismatic lens. Since the receiver is a photovoltaic device, a key aspect to be studied is the uniformity of receiver lighting: the power density measured in the image plane of the secondary optics evidences lateral zones of uneven lighting.
KeyWords: Efficiency; Lighting; Mirrors; Optical data processing; Solar heating, Collection efficiency; Concentration factors; Controlled conditions; Fresnel mirrors; Optical characterization; Optical measurement; Secondary optics; Solar concentration, Optical testing