Fresnel reflector

The idea of the Fresnel reflector is to divide a curved reflector into segments and to move these segments to a single joint plane [132, 133]. Thus one is able to effectively reduce a 3D object to a thin (quasi-2D) object while keeping the identical optical path to that of the 3D object. For instance, if one starts a 3D body of revolution like, for instance, a parabolic reflective concentrator or a Winston cone, this body can be divided into a number of annular segments which are subsequently placed concentrically on a flat surface. This process is illustrated in Fig. 2.12a, where a curved body is cut into segments and placed on a surface. An incident beam reflects under the same angles as it would from the full 3D body. 

Fresnel reflectors are much more compact and convenient than full 3D bodies of revolution or 2D troughs. They can be both of imaging and nonimaging type, depending on the body of revolution (or 2D trough) they approximate. 

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The effects of weathering at locations such as Florida and Arizona can be accelerated by using panel mountings that track the sun, combined with metal Fresnel reflectors to concentrate the rays of the sun, water sprays and cooling devices. This method is known by the initials EMMAQUA which stand for equatorial mounted mirrors with water spray (AQUA). By such means, one year of normal Florida weathering can be achieved in approximately 40 to 45 days [4] and this is therefore a very cost-effective method for materials needing a long service life. 

Fig. 2.12 Fresnel reflector, a Method of cutting reflective surface, b Reflective surface represented by in-plane curvilinear annular segments, c Reflective surface approximated by flat (blazed) segments with triangular profile...

D. Feuermann, J. Gordon, Analysis of a Two-Stage Linear Fresnel Reflector Solar Concentrator. J. Sol. Energy Eng. US 113(4) 272-279 1991... 

B. Negi, S. Mathur, T. Kandpal, Optical and thermal performance evaluation of a linear Fresnel reflector solar concentrator. Sol. Wind Technol. 6(5), 589-593 (1989)... 

Accelerated outdoor exposure testing (of various materials) using concentrated natural sunlight and a Fresnel reflector practice. 

Roofing membrane samples were exposed to up to 1800 MJoule of UV energy at the DSET Laboratories New River, AZ. Samples were placed in a Fresnel reflector device which accelerates the effects of natural sunlight. Spray cycle 2 described in ASTM G 90 was used. 

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