Energies, Vol. 19, Pages 1411: Energy, Exergy, and Environmental (3E) Analysis and Multi-Objective Optimization of a Recompression Brayton–Organic Rankine Cycle Integrated with a Central Tower Solar Receiver

Energies, Vol. 19, Pages 1411: Energy, Exergy, and Environmental (3E) Analysis and Multi-Objective Optimization of a Recompression Brayton–Organic Rankine Cycle Integrated with a Central Tower Solar Receiver

Energies doi: 10.3390/en19061411

Authors:
Jesús Alberto Moctezuma-Hernández
Rosa Pilar Merchán
Judit García-Ferrero
Julián González-Ayala
José Miguel Mateos Roco

This study develops and optimizes a hybrid plant that couples a recompression sCO2 Brayton cycle to a central-tower particle receiver with a bottoming Organic Rankine Cycle (ORC), including environmental and exergy balances. The two scenarios revealed Pareto points that raised the exergy efficiency to 0.65 in winter and reduced the fuel flow to 15 kg/s. Scenario number two achieves an overall thermal efficiency of 0.50 with total daily emissions of 2520 t CO2 and 2850 kg NOx, enabling nearly constant net power. Exergy destruction is concentrated in the high-temperature recuperator (HTR) and ORC turbines (27% each) and the ORC condenser (25%). Compared to a non-optimized baseline, the best solutions increased the ORC and Brayton efficiencies by 6.8–12.66% and 33.4–33.5%, respectively; cut gas-turbine power by 34% and ORC power to 10%; and lowered daily CO2 and NOx emissions by 52%. The gains stem from the coordinated adjustments of key levers: lower gas-turbine inlet temperature (about 10%), reduced Brayton mass flow (23%), and tuned ORC turbine inlet pressure.