Solar Concentrator

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Solar Concentrator When temperatures higher than 100°C are demanded, solar energy must be concentrated.9,10 The degree to which solar energy is concentrated by a given collector is called the concentration ratio and is defined as: C.R. = Collector Aperture AreaReceiver Surface Area Concentrators come in two basic configurations: parabolic troughs and parabolic dishes (Figure 10-6). Parabolic troughs are basically long sheets of metals bent along an axis to concentrate sunlight on a tube containing a liquid and placed along the focal line. Parabolic dishes are similar except that they are bent to form dishes. Since parabolic dishes distribute the energy over a smaller collector surface (around a focal point), they have a higher concentrating power than parabolic troughs. Furthermore, it is a matter of common sense that the bigger and more curved the collector area is, the higher the degree of concentration and collection efficiency will be. As Table 10-1 shows, parabolic dishes with concentration ratios as high as 1000:1 can be constructed; these can heat water to superheated steam at 1,200°C. Temperatures as high as 4,000 oC have been reached by a combination of various concentrator methods (Figure 10-7).

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