Thermo-exergoeconomic optimization and multi-criteria decision analysis of a hybrid ORC–Turboexpander system integrated into a Natural Gas Pressure Reduction Station

The present study develops and evaluates a hybrid Organic Rankine Cycle–Turboexpander (ORC–TE) system integrated into a Natural Gas Pressure Reduction Station (NGPRS) to recover both thermal and pressure-exergy losses. A comprehensive thermo-exergoeconomic model is formulated by coupling first- and second-law energy equations with component-level cost functions. The system performance is analyzed under steady-state conditions using a MATLAB–Engineering Equation Solver hybrid computational framework. Three conflicting objectives were simultaneously considered: maximizing Exergy Efficiency and Thermo–Environmental Synergy Indicator, while minimizing the total cost rate. The obtained Pareto fronts revealed strong coupling between thermodynamic enhancement and cost reduction, with an optimal compromise (Benchmark Case Study, BCS) Exergy Efficiency of 0.71, an Thermo–Environmental Synergy Indicator of 0.0275, and a Normalized Total Cost Rate of 0.47. A comprehensive sensitivity analysis identified the turbine isentropic efficiency and gas inlet temperature as the most influential parameters. To select the final operating configuration, a TOPSIS decision-making framework employing equal, entropy, and sensitivity-based weighting schemes was applied to the Pareto data. Among these, the sensitivity-derived weights produced the most stable and physically consistent ranking, yielding the highest normalized closeness coefficient of 0.73. Overall, the developed optimization framework demonstrates that the ORC–TE hybrid can achieve up to 84 % exergy efficiency with a 28 % reduction in total cost rate compared with the baseline Pressure Reduction Station, confirming its high techno-economic and environmental viability for industrial natural gas networks.