an insulated cavity is assumed to be at the focal point with helium gas passing through spirally wound tubes inside the cavity. A short flexible gas line connects the cavity to the closed cycle Brayton engine located at the counterweight position. A schematic of one module is shown in Figure 1. Electric energy would be collected from each Brayton engine and brought to the transmission terminal for power conditioning. The Brayton cycle operating at the current state-of-the-art temperature of 815°C is a relatively high efficiency (30 to 36%) device. An air heat exchanger, which is equivalent to a dry tower, it used to reject heat to the environment. Normally, ambient air will be heated from 20°C to about 120°C to cool this engine. The amount of power generated by economically attractive designs of a dish coupled to a Brayton engine is small by central plant standards. A dish which is 36 ft (11 m) in diameter can collect, over the day, about 52 kW of thermal power out of 74 kW of incident direct solar power. This figure is based on an annual average during the day for a good location in the Southwest. At a peak insolation 2 of 1 kW/m , the power collected would be 65 kWt. The use of a small closed cycle Brayton engine at each collector to avoid long-distance transport of high temperature heat limits the heat engine conversion efficiency to about 33%. Thus, an average of about 17 kWe is generated at each dish collector during the day. This combination of equipment has certain advantages compared to most central generation systems. These are the very short startup time and very low initial energy investment. Engine startup is accomplished in several minutes, rather than 10's of minutes or even an hour, after achieving full temperature in the working fluid. A solar plant which can generate electric power in the 10's of kWe at each dish can be used in a variety of ways. By using a large number of these modules (10,000's), large central station plants can be formed in remote areas to take advantage of good solar insolation. Substation power can be generated near an
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