A Hybrid AHP–WSM–TOPSIS Decision Framework for Optimal Gas Turbine Retrofit Selection under Conflicting Thermo-Economic Objectives

Abstract

Gas turbine retrofit planning involves complex trade-offs among thermodynamic performance, economic viability, and environmental impact, given conflicting objectives. Conventional retrofit studies often emphasize isolated performance indicators or rely on deterministic decision frameworks, limiting their applicability to real-world investment and operational planning. This study presents an integrated thermo-economic and multi-criteria decision-making (MCDM) framework for optimal selection of gas turbine retrofits, using the Omotosho gas turbine power plant as a real-world case study. Three advanced retrofit configurations—incorporating inlet air cooling, exhaust gas regeneration, heat- recovery steam generation (HRSG)-based steam injection, additional turbine stages, and dual combustion chambers — are modelled and evaluated against the baseline simple-cycle plant. Detailed thermodynamic simulations are performed using ASPEN HYSYS, while long-term economic performance is assessed over a 20-year operating horizon. To address conflicting objectives, the Analytic Hierarchy Process (AHP) is used to determine criterion weights, which are integrated into the Weighted Sum Method (WSM) and the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) for retrofit ranking. Results indicate that all retrofit configurations significantly outperform the baseline plant. The MGTP-1 configuration consistently demonstrates superior performance, achieving the highest thermal efficiency (47.44%), the most excellent net power output (157.08 MW), the lowest specific fuel consumption, and the highest net economic benefit. Both WSM and TOPSIS rank MGTP-1 as the optimal retrofit option, with sensitivity analysis confirming its robustness across varying operating conditions. The proposed framework provides a transparent, data-driven decision-support tool for identifying economically viable and environmentally sustainable gas turbine retrofit strategies