where air cooling can be used to eliminate dependence on water cooling.* This is an important characteristic in many arid regions of the Southwest where both land and solar insolation are available in greater than average quantities. The alternate concept in which a relatively small number of dish collectors (#50) can be used to drive a larger dosed cycle Brayton engine which would have lower cost and higher efficiencies may also be attractive, but is not evaluated in this report. The relatively short distances involved (~200 ft) could accommodate even an 800°C heat transport loop. A topping cycle is possible with a Brayton engine at each dish; water cooling could carry the waste heat at approximately 300°C to a central Rankine plant. Two basic concepts have been evaluated in this study in an attempt to bracket the cost and performance characteristics of solar power plants using parabolic dish collectors. They are distributed generation with a small Brayton engine at each collector, and central generation in which heat is collected from the field and delivered to a central Rankine power plant. The suitability of each approach only partially depends upon direct "overnight" construction costs. Questions of plant site (remote versus near urban), water availability (greater ease of using air cooling), plant reliability (many generators versus a single generator), total energy systems, and partial generation during construction all have a bearing on the attractiveness of these types of solar power plants. Only sun following plants are considered (i.e., no storage) in this report. These plants will be integrated with various storage systems in further studies. * A dry cooling tower can be used with the Rankine steam plant, but overall system performance will decrease about 10%, and the cost of the heat rejection subsystem will approximately double (see Section 4.2.2).
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