SECTION IV SYSTEM PERFORMANCE The various subsystems discussed earlier in Section 3 are considered as systems in this section. Preliminary economic-performance tradeoffs will be performed to sense optimum operating conditions. Both distributed and central generation will be evaluated. 4.1 BRAYTON DISTRIBUTED GENERATION SYSTEM 4.1.1 Sizing for Optimum Performance and Cost The first issue of concern is the optimum operating temperature of the combined parabolic dish and small Brayton engine. The collector performance is taken from Figure 7 for a concentration ratio of 1000 and a combined slope error of 0.32 degree. Figures 14 and 15 are representative of this type of closed cycle Brayton engine. The performance varies as indicated in Figure 14 also depends upon the capital intensiveness of the design. The dish performance has been combined with the Brayton engine performance versus temperature and the results are shown in Figure 18. The Brayton performance is shown for a range of designs represented by the "300$/kWe" to "400$/kWe." In both cases the optimum temperature is achieved near 815°0, which represents current near-term technology. There seems little incentive to drive the turbine inlet temperature higher since the combined efficiency does not improve. At 815°C the combined efficiency is 25.2%. The optimum size of the combined unit is the next parameter of interest. A value of 815°C is used as the optimum turbine inlet temperature and the cavity temperature is assumed to be similar to the fluid temperature. The collector cost versus size relationship has been taken from Figure 9, and the Brayton engine cost and efficiency versus size data were taken from Figure 14. Both 400$/kWe and 300$/kWe curves have been separately developed so that this parameter could
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