Solar Concentrator Research Paper

2.3 SOLAR CONCENTRATOR : Solar concentrator is a device which concentrates the solar energy incident over a large surface onto a smaller surface. The concentration is achieved by the use of suitable reflecting or refracting elements, which results in an increased flux density on the absorber surface as compared to that existing on the concentrator aperture. In order to get a maximum concentration, an arrangement for tracking the sun’s virtual motion is required. An accurate focusing device is also required. Thus, a solar concentrator consists of focusing device, a receiver system and a tracking arrangement .Temperature as high as 300C can be achieved using solar concentrators, and hence they have potential applications in both thermal

Thus the delicate part (the mirrors) of the system can be rigidly fixed. The image width at the absorber is ideally the same as projected the projected width of mirror element. Thus, the concentration ratio is approximately the same as the number of mirror elements, ignoring the solar beam spread .As the aperture is fixed and concave in shape ,the mirror strips result in shading with very high or very low sun altitude angles .Also due to strips ,edge losses occur during reflection .However, mirrors can be suitably designed to have less than 10% of the total energy lost over a years time .Some models have shown overall efficiencies in the range of

CYLINDRICAL PARABOLIC CONCENTRATOR : A cylindrical parabolic trough is a conventional optimal imaging device used as a solar concentrator. It consists of a cylindrical parabolic reflector and a receiver as its focal plane(fig).The receiver is backend at the outside surface and is covered by concentrator and rotated about one axis to track the sun's diurnal motion. The heat transfer fluid flows through the absorber tube, gets heated and thus carries heat. Such concentrators have been in use for many years. The aperture diameter, rim angle and absorber size and shape may be used to define the concentrator .The absorber tube may be used better performance .Depending on the temperature different heat transfer liquids may be used. Reflectors may be of anodized aluminium sheet, aluminized Mylar or curved silvered glass. Since it is difficult to curve a very large glass, mirror strips are sometimes used in the shape of parabolic cylinder. The reflecting part is fixed on a light weight structure. The concentration ratio for a cylindrical absorber varies from 5-30.

Figure 2.7 Cylindrical parabolic