Thermoeconomic analysis of a gas turbine and cascaded CO₂ combined cycle using thermal oil as an intermediate heat-transfer fluid

This paper reports an investigation of a gas turbine (GT) and two-stage cascaded supercritical and transcritical CO₂ (s-CO₂/t-CO₂) combined power cycle using liquefied natural gas (LNG) as a low-temperature heat sink. This cycle may be well-suited for installation near LNG import terminals. GT exhaust supplies input heat to an intermediate s-CO₂ cycle through a thermal oil loop. Waste heat from the s-CO₂ cycle and residual heat from the GT cycle drives a lower temperature t-CO₂ cycle. The t-CO₂ cycle is LNG-cooled. A solution procedure is performed to perform a coupled analysis of the thermodynamic and economic performance of this combined cycle. Results show that the GT-cascade CO₂ combined cycle has an optimal operating point determined by the s-CO₂ compressor inlet conditions. Genetic algorithm (GA) optimization indicates that a Taurus 60 GT-cascaded CO₂ combined cycle could reach 51.44% efficiency. For 20-year lifetime and 5% rate of interest, thermoeconomic optimization (after-tax profit, ATP as objective) results show ATP, levelized cost of electricity (LCOE) and net power are $2.935 × 10⁶, $0.0420 kWh⁻¹ and 8.886 MW, respectively. Findings suggest that the GT-cascaded CO₂ combined cycle is an efficient and commercially viable technology for power generation.