Al writes: "Stirling Energy Systems (SES), based in Phoenix, AZ, is building a prototype solar thermal plant that it hopes will make energy generation significantly cheaper. SES uses 12-meter-wide mirrors in the shape of a parabolic dish to concentrate sunlight onto a Stirling engine. The difference in temperature between the hot and cool sides of the engine drives pistons and generates 25,000 watts of electricity. The first phase of the company's large-scale projects will use 12,000 of these dishes to generate 300 megawatts of power. Ian Simington, the chairman of SES, expects electricity from the systems to cost between 12 and 15 cents per kilowatt hour, higher than the cheapest sources of electricity--such as coal-fired power plants--but competitive in many markets, especially in the afternoon, when prices are highest. Compared to several prototypes that have been tested for several years at Sandia National Laboratory, the new design cuts about two metric tons from the weight of each dish and reduces the number of mirrors in each from 80 to 40. The simplified design can be built in large quantities using equipment in existing factories for automobiles."