Multi-Objective optimization of a cascaded supercritical CO2 brayton cycle with ejector-enhanced transcritical CO2 and flash tank absorption refrigeration cycles

• Detailed design methodology of a novel cooling and power generation system. • Improvement of power cycle efficiency by generating additional cooling load. • Minimization of exergy loss in power cycle by recovering waste heat. • Analysis on influence of operating conditions on the integrated system. • Identification of optimal parameters to maximize thermal and exergy efficiencies. The research introduces a novel system that combines power generation and cooling system by integrating an ejector-assisted transcritical CO 2 refrigeration (ETCR) subsystem and a flash tank installed compression absorption refrigeration (FCAR) subsystem, cascaded with a supercritical CO 2 recompression Brayton cycle. The FCAR subsystem contributes additional cooling capacity, while the ETCR subsystem enhances the chiller load by minimizing waste heat from the cooler. These added loads significantly enhance the system’s overall power output, leading to higher thermal and exergy efficiencies. The thermal performance of the integrated system is evaluated through extensive parametric analyses implemented in Python, considering variables such as turbine and compressor inlet temperatures, minimum pressure, pressure ratio, evaporator temperature, and the generator’s hot and cold-end pinch temperatures. Multi-Objective Optimization (MOO) is used to identify the ideal operational parameters for maximizing thermal and exergy efficiencies. For MOO and Multi-Criteria Decision Making (MCDM), the Non-dominated Sorting Genetic Algorithm II (NSGA-II) and TOPSIS methods are used, respectively. The optimization results indicate that the system achieves peak performance when the compressor entry temperature is set at 33.03 °C, and the pressure ratio is 3.52. Under these optimal conditions, the system attains thermal and exergy efficiencies of 61.8 % and 65.76 %, respectively. With a 100 MW input power, the system delivers a net output of 40.52 MW, along with a chiller load of 10.96 MW and a cooling load of 10.32 MW, leading to 16.14 % greater thermal efficiency and 4.4 % improved exergy efficiency over a conventional system. Additionally, exergy analysis identified a total exergy destruction of 26 MW, with significant losses observed in the reactor and R41 evaporator (10.24 % and 5.48 %, respectively). Under optimal conditions, the system can produce 40.52 MW of total work, a 10.96 MW Chiller load, and a 10.32 MW cooling load, requiring 100 MW of input heat to the system’s heaters.