for the _T equal to 110°C case. A similar exercise for △T equal to 55°C and c 28°C corrects the direct costs to 52$/MWt and 57$/MWt, respectively. The cavity heat exchanger has pressurized water with forced convection heat transfer in a low cost carbon steel piping at a maximum temperature of 315°C. The cavity receiver is estimated to cost 14$/kWt. The rated incident energy on each 1000 ft (36 ft diameter) collector is 74.4 kWt without blockage. With a GCR of 0.4, the blockage factor is 0.95 as shown in Figure 21 , which is based on Reference 1. The sun following type of operation at 120% of rated capacity will lose some of the annual peak energy. This is estimated to be 0.975 for the clear Southwest region. Combining these effects, the 36 ft. diameter dish collector delivers 55.7 kWt to the fluid with an assumed 81% efficiency at 315°C. Based on this, the cavity receiver adds $760 to the power plant cost. The 11.50$/ft dish cost corrected to 1975 dollars is $12,760. The total cost of each collector and receiver combination is $13,320. For the case of △T = 55°C the heat collected for a net output of 150 MWe is 484 MWt. This includes an allowance of 1.7% for pumping power and 6.2% for transport heat losses. Since the Rankine plant will operate most of the time at an off design condition, a correction factor of 0.98 was applied for off-load performance. The basic Rankine plant efficiency is 34.3% (see Section 3.3.2.1). When all these factors are considered, 454 MWt must be delivered to the central heat engine to generate 150 MWe. To do this, 8686 collectors are needed at 55.7 kWt each. The cost of the entire field of collectors plus receivers is $115.7 million, giving a capital cost of 771$/kWe. The Rankine heat engine is considered to cost 175$/kWe. Correcting for the over-capacity needed for pumping and off-load inefficiency, the cost becomes 182$/kWe. The heat delivered is 454 MWt. At 52$/kWt, the heat transport cost is $23.6 million. This reduces to 158$/kWe. The total cost for these three
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