This is the fraction of focused energy intercepted by the absorber of a given size. B jI (x)dx g = fy (2.37) I(x)dx —infinity For a typical concentrator-receiver design, the value of у depends on the size of the absorber, g usually has a value greater than 0.9. If the solar radiation is normal to […]

This is defined as the ratio of the collecting aperture surface area to the area of the absorber surface. The values of C vary from unity (FPC, C = 1) to several thousand (parabolic dish). As shown in Figure 2.18, let us consider the circular concentrator with aperture area Aa and receiver area Ar. It […]

Definitions of the terms that characterise concentrating solar collectors are given below: 2.6.1.1 Aperture Area (Aa) This is the plane opening of the solar concentrator through which the incident solar flux is received. It may be defined by the physical extremities of the concentrator. 2.6.1.2 Acceptance Angle (2 Qc) This is the limiting angle for […]

A solar concentrator is a device that concentrates the incident solar energy over a larger surface area onto a smaller surface area, unlike a FPC. Further, it is important to mention too that the area of absorber and glass cover is not the same as in the case of a FPC (i. e. Ac<Aa). In […]

The schematic of a conventional air heater is shown in Figure 2.17. The air flows in a parallel passage below the absorber as discussed in case (ii). The performance analysis of a solar air col­lector does not include the fin effect or the tube-to-plate bond conductance as mentioned in the case of liquid FPCs. The […]

The air passage below the absorber is the most commonly used solar air collector. A plate parallel to the absorber plate is provided in between the absorber and the insulation, thus forming a passage of high aspect ratio (Figure 2.15b) for the air flow. Case (iii): Both sides of absorber In another variety of nonporous […]

A solar air collector is basically a FPC with an absorber plate, a transparent cover at the top and insulation at the bottom and on the sides. The whole assembly is encased in a sheet-metal container. The working fluid is air. The material for construction of air heaters is similar to those of liquid FPCs. […]

The basic description and analysis of some solar air heaters used for space heating and crop drying has been discussed. The solar air heaters have certain advantages and disadvantages over the liquid FPC. These are as follows: (A) Advantages (i) Simple system: It is compact, cheap and less complicated. (ii) Corrosion: It can cause serious […]