SECTION III SUBSYSTEM PERFORMANCE CHARACTERISTICS The three major subsystems associated with the parabolic dish solar collector power plant are the collector itself, the energy transport subsystem and the heat engine. Each of these subsystems is discussed below and they are integrated for performance in Section 4. The technical performance of each subsystem and the state-of-the-art are considered along with the projected economics. 3.1 PARABOLIC DISH AND CAVITY COLLECTOR SUBSYSTEM 3.1.1 Performance The performance of this type of collector is shown in Figure 7. The collector thermal efficiency is shown versus collection temperature for several concentration ratios. The inherent assumptions are the following: 1) Glass transmissivity = e , where K (extinction coefficient) = 0.6 and T is the glass thickness (0.05 inches) 2) Silver reflectivity = 0.90 3) Cavity receiver absorptivity = 1.0 (black body) 4) Direct solar flux = 0.080 W/cm2 (254 BTU/hr-ft2 ) 5) 5% conduction and convection heat leak from cavity and the lines to the Brayton engine The reflectivity of a 0.05 inch thick plate of glass which was backsilvered was reported to be 0.94 in tests conducted early 1975 at JPL. The cavity receiver is nearly a black body, and the major heat loss mechanism from such a heat receiver is radiation through the aperture. Convection and conduction are small for an insulated cavity. Even the non-cavity receiver in Reference 1 operating at 815°C with a concentration ratio of 1000 has a heat leak of only 0.75 kW out of the 20 kW which are absorbed. This is about 4%; the
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