Marine engine efficiency improvement with supercritical-CO2 Rankine waste heat recovery

The efficiency of marine energy systems gains more and more importance considering economic and environmental effects. Additional power is produced by annexation of a supercritical CO2 Rankine cycle (sCO(2)-RC) via utilisation of the exhaust of a marine engine. A parametric study on sCO(2)-RC is carried out to optimise objective functions such as ECOP, maximum net power output with respect to the outlet temperature of the exhaust stack, and the maximum pressure of the cycle. Then, energy and exergy analyses are applied to the system. Results show that the sCO(2)-RC system improves thermal efficiency by 8.17% and provides a 7.54% better fuel economy, while exergy efficiency of the sCO(2)-RC is 51.3% with a net power output of 321.7 kW and ECOP of 1.09. Hence, the results lead to the optimisation order of the investigated system components for the improvement in overall efficiency, and the reduction of fuel consumption and environmental effects.