System 1. Pressurized Hot Water Transport In this heat transport concept pressurized water (liquid) exits from the collector at 315°C with a pressure in excess of 1545 psia. The hot water is collected to a central site, passes through a heat exchanger (steam generator) and vaporizes a working fluid in the Rankine power cycle. Alternatively it is flashed and becomes the working fluid. The return line contains water at a temperature of approximately 200°C. Both hot and cold lines can be fabricated from carbon steel piping; thermal insulation is required. System 2. Steam Transport with Water Return In this concept the collector subsystem produces superheated steam at 510°C. This steam is fed to an accumulator (thermal flywheel to accommodate transitory insolation fluctuations) and then is piped directly to the turbine generators. The cold return loop from the condenser is at a temperature in the range of 40°C to 260°C. The hot loop at 510°C will be fabricated from low alloy steel which is about four times more expensive than carbon steel for equivalent size pipe, and will be insulated. The liquid water return piping will be carbon steel. System 3. Liquid Metal Transport In this concept liquid metal (NaK) flows through a stainless steel heat collection-transmission loop. The stainless steel is necessary to resist corrosion attack by the hot liquid metal. The hot loop is assumed to be at a temperature of 650°C and the cool loop is at a temperature of approximately 370°C. Some severe technical problems (such as system reliability and safety problems) may exist if a liquid metal transport system is used. These have not been considered in the economic analysis. Special consideration must be given to all heat exchanger and collector piping components in contact with the NaK; it is necessary that these components be fabricated from stainless steel. The NaK does not require
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