Category: 3.Solar Energy Collectors

The analysis presented here is based on Bejan’s work (Bejan et al., 1981; Bejan, 1995). The analysis, however, is adapted to imaging collectors, because entropy generation minimization is more important to high-temperature systems. Consider that the collector has an aperture area (or total heliostat area), Aa, and receives solar radiation at the rate Q∗ from the sun, as shown…

As we have seen in Section 3.2, concentrating collectors work by interposing an optical device between the source of radiation and the energy-absorbing surface. Therefore, for concentrating collectors, both optical and thermal analyses are required. In this book, only two types of concentrating collectors are analyzed: compound parabolic and parabolic trough collectors. Initially, the concentration ratio…

or various reasons, the actual performance of an FPC may be different from the one obtained from the theoretical analysis presented in this section. The first reason is that the fluid flowing through the collector may not be uniform through all risers due to manufacturing errors. The section of the collector receiving a lower flow…

A schematic diagram of a typical air-heating flat-plate solar collector is shown in Figure 3.33. The air passage is a narrow duct with the surface of the absorber plate serving as the top cover. The thermal analysis presented so far applies equally well here, except for the fin efficiency and the bond resistance. FIGURE 3.33 Schematic diagram…

In this section, the thermal analysis of the collectors is presented. The two major types of collectors, flat plate and concentrating, are examined separately. The basic parameter to consider is the collector thermal efficiency. This is defined as the ratio of the useful energy delivered to the energy incident on the collector aperture. The incident…

Energy delivery temperatures can be increased by decreasing the area from which the heat losses occur. Temperatures far above those attainable by FPCs can be reached if a large amount of solar radiation is concentrated on a relatively small collection area. This is done by interposing an optical device between the source of radiation and the…

Solar energy collectors are basically distinguished by their motion—stationary, single-axis tracking, and two-axis tracking—and the operating temperature. First, we’ll examine the stationary solar collectors. These collectors are permanently fixed in position and do not track the sun. Three main types of collectors fall into this category: 1. Flat-plate collector (FPC). 2. Stationary compound parabolic collector (CPC). 3. Evacuated…