An additional consideration for the distributed generation approach is that it is modular at the 20 kWe size level. It can fit irregular sized land in remote or in urban areas. Also, it has a low visual profile (~ 36 ft diameter dish) with no large buildings or cooling towers. It is air cooled and can be used for total energy systems to supply electric power and heat to community, commercial and industrial sites. It has a quick startup (several minutes). The capacity at a particular site can be built up gradually. The dish collector requires development as does the closed cycle Brayton engine. The electric power collection equipment is available. The central generation approach (steam or chemical) should be used in a size greater than 100 MWe, and can use a single, large,relatively circular plot of land. It has large buildings and cooling towers in the center of the solar field. The energy transport subsystem and Rankine plant technologies are available. The chemical thermal dissociation and recombination (catalyst) components must be developed for this application. Both systems may start up in less than 1 hour if the Rankine plant is preheated in some manner. Several approaches are possible for the thermal link between the dish cavity receiver and local heat engine (distributed generation), or to the fixed piping network for the central generation approach. Candidate approaches are a flexible fluid line, or a fixed cavity receiver on a probe through a slot in the dish surface, or a Cassegrain reflection of energy to a small heat engine hung at the counterweight position with a flexible electric connection to the ground, or a double mirror Cassegrain approach where the cavity is fixed on the ground. A detailed design-costing study should be carried out to choose the best approach in this area. 2 Major uncertainties exist in the area of dish collector cost. Nearly $13/ft was estimated (no cavity), but estimates varied widely. Also the small Brayton
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