Comparison of advanced engines for parabolic dish solar thermal power plants

A paraboloidal dish solar thermal power plant produces electrical energy by a two-step conversion process. The collector subsystem is composed of a two-axis tracking paraboloidal concentrator and a cavity receiver. The concentrator focuses intercepted sunlight (direct, normal insolation) into a cavity receiver whose aperture encircles the focal point of the concentrator. At the internal wall of the receiver the electromagnetic radiation is converted to thermal energy. A heat engine/generator assembly, which is mounted directly behind the receiver, then converts the thermal energy captured by the receiver to electricity. Developmental activity has been concentrated on relatively small power modules which employ 11- to 12-m-diam dishes to generate nominal power levels of approximately 20 kWe. A comparison of advanced heat engines for use on the dish power module is presented in terms of the performance potential of each engine as weighed against its requirements for advanced technology development. Three advanced engine possibilities are considered. These are the Brayton (gas turbine), Brayton/Rankine combined cycle, and Stirling engines. All three engine candidates are attractive in terms of overall system performance potential.