system cost was taken as the sum of the direct capital construction cost, and the cost of the heat leak and pumping power. The construction cost includes pipe, installation labor and fluid charge costs. The parametric evaluation of these three variables for each of the five fluid systems chosen was performed with the aid of a digital computer. The collector performance, solar insolation and ground cover ratio were also varied to determine cost sensitivity to these external parameters. This analysis was done for the three system sizes identified earlier. Appendix A contains the mathematical details of this calculation. The results and discussion of this analysis are contained in the following section. 3.2.1.2 Pipe Network and Cost Data. The technique described in Section 3.2.1.1 was applied to the five energy transport subsystems. The annual direct solar insolation rate used in this analysis is an average of 10 BTU/ft year (2740 BTU/ ft -day), which equals 8.62 kWh/m -day. This is felt to be representative of good locations in the Southwest for a solar tracking system, and the value is based on several years of weather data from this area. Based on an average solar load factor of 0.45 for tracking collectors, the average insolation over the 3940 hours per year that the transport system is collecting energy is 254 BTU/ft -hour = 0.798 kW/m^ = 3.24 MW/acre. A 36 ft diameter dish would intercept energy at the rated power of 75 kWt if this energy were averaged over 10.8 hours per day. The collector pipe network for each of the five considered systems is described by Figure 10. For the 512 collector case, each square is 47 feet on a side since each collector is assumed to be a circular parabolic dish with a diameter of 36 feet. The effective collector ground cover ratio (GCR) is 0.46 which produces about 7.2% shading of the collector averaged over the year.
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