Thermodynamic and Economic Analysis of Advanced and Externally Fired Gas Turbine Cycles

Abstract

The thermodynamic performance of a number of advanced gas turbine cycles and equivalent externally fired cycles has been studied to derive optimum efficiencies and work outputs. With external firing, significant improvements in the performance of the advanced cycles over the simple gas turbine cycle were found, demonstrating the potential of such cycles for effective power generation from biomass or other dirty fuels. Cost comparisons have been made and the minimum cost of electricity from each cycle calculated with discounted cash flow. The externally fired cycles benefit from low fuel costs which give favourable electricity costs, although development costs for the high-temperature heat exchanger and other advanced cycle components are likely to be significant. The gas—steam combined cycle when externally fired was found to give the lowest cost of electricity for large-scale generation, with the steam injected and humid air turbine cycles competitive on smaller scales.