pressurization and a line pressure of 100 psia has been assumed. System 4. Hot Inert Gas Transport For this concept helium is heated by the solar collector system to 650°C and returned from the power generation system at a temperature of approximately 370°C. The pressure must be as high as the pipes will allow in order to maintain the highest possible density (which reduces pipe size and required pump work); a pressure of 1500 psia has been considered in this study. The hot line is composed of low alloy steel and the cooler return line uses carbon steel. System 5. Chemical Transport Although there are many chemical systems which could be used,the methane approach is used as an illustrative example. Heat from the solar collector at 700°C causes a mixture of methane (CH^) and steam (H20) to thermally dissociate to hydrogen (H2) and carbon monoxide (CO). Thus,a large quantity of heat is stored chemically and this heat in turn is released after transport to a central site where the H2 and CO are passed through a catalyst bed and reacted chemically with each other. After the hot reaction products (with stored chemical energy) leave the collector they are passed through a heat exchanger and their sensible heat is transferred to the incoming reactants. The incoming reactants were previously at ambient temperature as they moved from the central plant to the collectors in the field. Thus, all transport lines between the dish collectors and the Rankine plant are at ambient temperature and do not require insulation or expansion loops. The energy transport subsystem analyzed is shown in Figure 6. Condensed water is separated from the gas whenever possible and run through a separate line; thus, there is one line containing product gases leading from the collector, and two lines containing CH4 (gas) and water (liquid) returning to the collector. The pressure will be 1500 psia in all lines, and the pipe material will be carbon steel. Since most of the heat from the collector goes into chemical storage with a high reaction enthalpy, the system
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