Thermodynamic and economic comparative analysis of air and steam bottoming cycle

•The subject of the paper was a comparison of air and steam bottoming cycle.•Gas turbines find application in commercial gas turbine steam bottoming cycles.•Calculations include design study of air bottoming cycle heat exchangers.•Area where air bottoming cycle is economical competitive is determined.•Water and air cooling system of air bottoming cycle is presented.

Article presents a comparative thermodynamic and economic analysis of air and steam bottoming cycle of a gas turbine. In order to make the comparison between air and steam bottoming cycle, identical gas turbines were selected. A decision was made to use gas turbine sets with a power output capacity included in the range of 5–25 MW. Considering that the air bottoming cycle agent is characterized by a low heat capacity, the systems under analysis have a better chance of competing with steam bottoming cycle configurations in the small power output capacity range. The gas turbines used in the calculations find application in commercial gas turbine steam bottoming cycles. Article includes results of the thermodynamic optimization of gas turbine air bottoming cycle. Calculations include design features of air bottoming cycle heat exchangers. The most essential aspect of the analysis is the economic comparison. The results are compared to performance characteristics of real gas turbine steam bottoming cycles. Quantities are determined that have a decisive impact on the considered units profitability and competitiveness compared to the popular technology based on steam bottoming cycle systems. The ultimate quantity that can be compared in the calculations is the marginal cost of electricity.