Fresnel lense

Optics. Good optical properties and low thermal resistance make poly(methyl methacrylate) polymers well suited for use as plastic optical fibers. The manufacturing methods and optical properties of the fibers have been reviewed (124) (see Fiber optics). Methods for the preparation of Fresnel lenses and a Fresnel lens film have been reported (125,126). Compositions and methods for the industrial production of cast plastic eyeglass lenses are available (127). 

Oliveira P.W., Krug H., Kunstle H., Schmidt H., The production of Fresnel lenses in sol-gel derived ormocers by holography, SPIE Proc. 2288, 554-562, (1994). 

Thermoplastic cyclic olefin polymers can be used for a wide range of applications, such as wire coating materials, agricultural films, and packaging films, and toner resins. Further, optical applications such as plate lenses, including Fresnel lenses have been described (6). 

Focusing collectors are usually cast acrylic Fresnel lenses, or mirrors of aluminized polyester film in frames of aluminum. These reflectors are either enclosed in a bubble of poly(vinyl fluoride) film, or under polycarbonate glazing, which may be covered with a fluorocarbon film to reduce the reflectivity. The absorbers for active systems are copper or aluminum since the temperatures are too high (325—370°C) for plastics. The frames, however, can be molded ABS, high density polyethylene or polyurethane, either solid or structural foam. Polybutylene or chlorinated PVC can be used for piping hot water, and tanks can be made of either reinforced polyester or blow- or rotational-molded, high density polyethylene (12—15). 

The Fresnel lens concentrator, shown in Figure 1.36 top right, uses refraction rather than reflection to collect the solar energy. These units are molded out of inexpensive plastic and provide higher efficiency than the standard PV collectors. Point-focusing Fresnel lenses are also available. In Figure 1.36 bottom left, parabolic dish collectors are shown. Both the Fresnel lenses and these collectors can be rotated around two axes to continuously track the Sun. 

Fig. 1. Several 35-kilowatt (kW) CPV systems built by Amonix in Torrance, California, are installed at an Arizona Public Service power plant. The system uses Fresnel lenses to concen trate sunlight. The pickup truck in the shade gives an idea of size.

Fig. 18. Schematics of the fabrication of micro fresnel lenses by two-wave mixing, [35]...

Leutz R, Suzuki A (2001) Nonimaging fresnel lenses - design and performance of solar concentrators. Springer, Berlin... 

In the following chapters both worlds (the present micro- and the future nano-world) are shown, from the perspective of lateral structures using laser ablation and/or the specially designed polymers. Selected examples/applica-tions of microstructures (diffractive gratings, Fresnel lenses) and possible future writing techniques (AFM and SNOM) are presented. 

An example of Fresnel lenses etched into the triazene polymer is shown in Fig. 95. The ablation structures are well defined (shown in Fig. 95, left),... 

The combination of gray-tone phase masks with the highly sensitive photopolymers is suitable for the fast fabrication of three-dimensional topographies. Single laser pulses can create complex structures, such as Fresnel lenses. A pattern transfer into glass or quartz, e.g., by proportional etching techniques, would open an even larger spectrum of applications. 

Bonse U, Riekel C, Snigirev AA (1992) Kirkpatrick-Baez microprobe on the basis of two Unear single crystal Bragg-Fresnel lenses. Rev Sci Instrom 63 622-624 Borg LE, Connelly JN, Nyquist LE, Shih CY, Wiesmann H, Reese Y (1999) The age of the carbonates in martian meteorite ALH84001. Science 286 90-94... 

The photovoltaic power system consists of 160 single pedestal concentrator arrays, each containing 256 circular silicon solar cells (64 modules). Each module contains 4 Fresnel lenses, for a sunlight concentration of ca. 33 times over solar cells. These 64 branches are connected in parallel to provide 350 kW of peak power. The electrolysis system is a commercially available HS 2000 electrolyzer with the cell area 0.2 rrfi (No. of cells 144). Electrolyte is 30% KOH solution, system pressure 6 bar, working temperature 100 °C. The plant also contains a grid operated rectifier for initial start-up and special testing. 

Use is made of a heliostate to track the sun and of a solar concentrator (Fresnel lenses). Electrolyzer is of a filter-press type. Electronic matching device. 

Large-size high-aperture condenser systems in projeetors often use Fresnel lenses. A Fresnel lens is a flat piece of plastic with concentric grooves that act as individual refracting surfaces (Fig. 7.8). 

Polymers have many potential applications In solar technologies that can help achieve total system cost-effectiveness. For this potential to be realized, three major parameters must be optimized cost, performance, and durability. Optimization must be achieved despite operational stresses, some of which are unique to solar technologies. This paper Identifies performance of optical elements as critical to solar system performance and summarizes the status of several optical elements flat-plate collector glazings, mirror glazings, dome enclosures, photovoltaic encapsulation, luminescent solar concentrators, and Fresnel lenses. Research and development efforts are needed to realize the full potential of polymers to reduce life-cycle solar energy conversion costs. 

Fresnel Lenses. Fresnel lens concentrators have been studied for both theimial and photovoltaic systems. The economic viability of their use depends on a large number of system-related factors, Including the performance, cost, and durability of the lenses. Performance requirements Include minimum absorption, scattering, and surface reflection. Total cost depends on costs of materials and fabrication, or minimum thickness defined by mechanical requirements, and on additional material required for optical design. Like other solar applications of optical polymers, durability for extended periods Is required. 

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