Advanced Thermo-Exergo-Economic Optimization of Regenerative Dual-Turbine Gas Turbine Cycles under Tropical Operating Conditions

Abstract

Gas turbine power plants operating in tropical regions experience persistent performance degradation due to high ambient temperatures, increased compressor work, and intensified thermodynamic irreversibilities, collectively reducing efficiency and increasing operating costs. While conventional energy-based analyses indicate that cycle modifications can enhance performance, they do not adequately identify the sources of inefficiency or their economic consequences. This study presents a comprehensive thermos-exergo-economic optimization of a real industrial gas turbine power plant operating under sustained tropical conditions. Five years of operational data from the Omotosho gas turbine power plant in Nigeria were used to develop and validate detailed ASPEN HYSYS models for a conventional Brayton cycle and three advanced retrofit configurations incorporating inlet air cooling, regeneration, heat- recovery steam generation, steam injection, dual combustion chambers, and staged turbine expansion. Component-level exergy and exergoeconomic analyses were conducted, followed by multi-objective optimization using the Non-dominated Sorting Genetic Algorithm II (NSGA-II) to maximize exergetic efficiency and minimize the cost of exergy destruction. The results show that the configuration combining inlet air cooling, regeneration, steam injection, and dual turbine expansion achieves the lowest exergy destruction and the highest exergetic efficiency, improving second-law efficiency by more than 40% relative to the conventional cycle. A well-defined Pareto-optimal operating region with exergetic efficiencies above 45% is identified without excessive economic penalties, providing practical guidance for gas turbine retrofits in hot-climate power systems