Thermoeconomic analysis of mixed gas–steam cycles

Abstract In this paper the direct thermoeconomic analysis approach developed by the authors [ASME Paper 95-CTP-38; ASME Cogen Turbo Power Conference, Wien, 23/25 August, 1995] is applied to the assessment of the thermoeconomic performance of mixed gas–steam cycles such as the steam injected cycle (steam injected gas turbine, STIG), regenerated water injected (RWI) cycle, and humid air turbine (HAT) or evaporative cycle. All the simulations were carried using the thermo-economic modular program (TEMP) code developed at the University of Genoa [ASME Trans., J. Engng. Gas Turbine Power 119 (1997) 885; Thermo-economic and environmental optimisation of energy systems, Tesi di Dottorato, Universita di Genova (DIMSET), 1997] and carefully tested here, mainly for the HAT cycle and saturator, using the experimental data provided by the HAT pilot-plant operating at the Lund University, Sweden [Theoretical and experimental evaluation of the EvGT-process, Thesis for Degree of Licentiate in Engineering, Lund Institute of Technology, Sweden, 1999; Evaporative cycles – in theory and in practice, Doctoral Thesis, Lund Institute of Technology, Sweden, 2000]. Three different mixed cycles (STIG, RWI, and HAT) are analysed in detail together with an additional fourth layout proposed by the authors [Thermoeconomic analysis of STIG, RWI and HAT cycles with carbon dioxide (CO 2 ) emissions penalty, Tesi di laurea, Universita di Genova (DIMSET), 2000], named HAWIT, humid air water injection turbine, that appears to be the most attractive solution. The thermoeconomic results of mixed cycles are presented here for the first time in open literature. These results are compared to the data of a conventional two-pressure level combined cycle considered as representative of the state of the art of high efficiency conversion systems. A new representation proposed by the authors [ASME Trans., J. Engng. Gas Turbine Power 122 (2000)], such as cost of electricity versus cycle efficiency or internal rate of return versus electric efficiency, is used to demonstrate the main features of these types of innovative energy plants.