Performance analysis of variable speed solar gas turbine configurations.

In solar gas turbines, the conventional integration of the core compressor and turbine into a single "spool" can impede optimal flow through the blade passages in the components for a given thermal energy input and load. This affects the efficiencies of the compressor and turbine components, and the performance of other components in the flow circuit that are sensitive to the pressure and mass flow rate of the working fluid, such as the solar receiver. In principle, flow compatibility between the various components in a solar gas turbine can be improved if the compressor and turbine rotor speeds can be made to adapt to changing conditions in the flow circuit. Such deconstructed configurations are used in electrically assisted turbochargers and appear in various concepts for next-generation jet engines. In this work, different variable speed gas turbine configurations are simulated, and their performance compared with that of conventional single- and two-shaft engines to quantify the improvement, if any, that can be attained. The findings show that variable rotor speeds can enable the average quantity of thermal energy harnessed by the solar receiver to be increased by 8.46 %, and the average fuel consumption in solar hybrid operation to be reduced by 15.1 % compared to the reference. The effects of the component sizes on the observations are described, limitations of the analysis are identified, and possible implications of the findings for the costs and emissions of solar gas turbine systems are discussed. [ABSTRACT FROM AUTHOR]