Thermodynamic analysis and multiobjective optimization of a solar-driven PTC–ORC–desalination multigeneration system with ternary working fluids

This study investigates a solar-driven multigeneration system integrating a parabolic trough collector, an organic Rankine cycle (ORC), and a thermal desalination unit to produce electricity, freshwater, and useful heat. The main contribution is the utilization of a ternary working-fluid mixture (R152a/R1234yf/R600a) and the systematic multiobjective optimization of its mass fractions. A comprehensive thermodynamic model was developed, validated, and evaluated for two representative operating days, 21 December and 21 June. Weighted-sum multiobjective optimization was performed across three scenarios. The power-priority and water-priority scenarios yielded optimal mass fractions of 0.45/0.34/0.21 and 0.41/0.26/0.33, respectively. The balanced scenario, weighting net power output, condenser heat duty, and freshwater production rate equally, identified a recommended composition of 0.38/0.22/0.40 with an aggregate index of 0.7076. Under this optimal mixture, the system delivered a net power output, condenser heat duty, and freshwater production rate of 1060 W, 13,870 W, and 20.45 kg h −1 on 21 December, and 1475 W, 19,750 W, and 28.80 kg h −1 on 21 June, respectively. The recommended mixture also showed a low mass-weighted global warming potential of 54 and lower cost compared to pure R1234yf. Furthermore, component-level exergy analysis identified the solar collector field as the dominant source of irreversibility, accounting for 68.5% and 73.2% of the total exergy destruction on 21 December and 21 June, respectively, followed by the ORC boiler with 12.8% and 10.5% shares. These results demonstrate that while composition optimization balances system yields, future thermodynamic improvements should focus on solar collection and heat addition.