Optimization of a Hybrid Recompression Supercritical Carbon Dioxide–Organic Rankine Cycle Regenerative Combined System

To efficiently recover waste heat from gas turbines, a hybrid recompression supercritical carbon dioxide (SCO2)–organic Rankine cycle (ORC) regenerative combined system is proposed. The ORC employs a mixed working fluid to enhance thermodynamic matching. Thermodynamic, compactness, and economic models are established to analyze the influence of key operating parameters on system performance. Based on parametric analysis, decision variables are identified and used for single-objective and multi-objective optimizations of system performance metrics. Results show that increasing the split ratio in the recompression cycle improves thermodynamic performance but simultaneously increases both heat transfer area per unit output power (APR) and the levelized electricity cost (LEC). In the ORC, the temperature glide during evaporation and condensation of the mixed working fluid enables better thermal match with the heat source and sink, thereby reducing the required heat transfer area and associated cost rate. Under multi-objective optimization targeting APR and LEC, the optimal decision variables are determined as 560 °C, 4.2, 0.71, 44 °C, and 0.71, respectively.