Exergoeconomic and environmental optimization of gas turbine-based CCHP systems: A comprehensive study with multi-objective optimization and decision making

Abstract

This study comprehensively assesses two gas turbine-based combined cooling, heating, and power (CCHP) systems, employing exergoeconomic and environmental evaluations. Utilising a dedicated in-house code within the MATLAB environment, the study conducts a thorough performance analysis of the CCHP systems under base case operating conditions. The base case results demonstrate the superiority of the first system over the second system in various aspects. Exergy analysis indicates the combustion chamber as the key source of irreversibility, accounting for more than 70 % of exergy destruction in both systems, emphasising the need to address combustion-related inefficiencies. Furthermore, the Non-dominated Sorting Genetic Algorithm-II (NSGA-II) is used to perform multi-objective optimisation of both systems, taking system cost rate and normalized CO2 emissions as objective functions. The investigation encompasses ten optimisation runs for each system, followed by statistical analysis to ensure methodological reliability. The multi-criteria decision analysis is also performed to select the final optimal solution from the Pareto fronts by using a novel approach of integrating Entropy method with Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) decision-maker. The study showcases the significant improvements in system performance and environmental impact achieved through multi-objective optimization. Both systems experience around 8–9 % reductions in system cost rates and around 1.5–2 % reduction in the normalized CO2 emissions. Scattered distribution plots highlight the trade-offs amongst key decision variables, particularly the pressure ratio and isentropic efficiency of the air compressor. In conclusion, this research offers valuable insights into the performance, efficiency, and optimization potential of CCHP systems.

Keywords

• CCHP systems
• Gas turbine
• ORC
• NSGA-II
• TOPSIS