A solar-power-tower plant is considered for Houston, Texas. Heliostats with a total area of 400,000 ft2 are to be used to reflect solar radiation into a receiver. When the solar irradiation is 250 Btu/h·ft2, steam is produced at 160 psia and 600oF at a rate of 15 lbm/s. This steam is expanded in a turbine to 2 psia pressure. The isentropic efficiency of the turbine is 88 percent.
(a) Determine the power output, in kW and the thermal efficiency of the plant under these operating conditions.
(b) How much electricity can be produced per year if the average thermal efficiency is 12 percent and the generator efficiency is 98 percent? Use the solar insolation values in Table 18-4.
(c) The estimated cost of this plant is $17,000/kW and the plant is expected to operate 4500 h a year at the power output determined in part (a). If electricity generated is to be sold at a price of $0.11/kWh, how long will it take for this plant to pay for itself?