Shipboard waste energy recovery for power and cooling supply as a strategic response to greenhouse gas pricing mechanisms

This study develops and assesses a comprehensive waste energy recovery system for a liquefied natural gas (LNG) carrier vessel, aiming to enhance energy efficiency and reduce pollutant emissions under current and forthcoming greenhouse gas (GHG) pricing mechanisms. The proposed configuration integrates four subsystems to simultaneously recover cold and thermal energy from the auxiliary dual-fuel engine and the LNG fuel regasification process. A customized Claude cycle employing nitrogen as a safe and inert working fluid was designed to recover cold exergy for both electricity generation and provision refrigeration. In parallel, a low-temperature organic Rankine cycle was implemented to exploit the residual cold energy of regasified LNG, with a focus on environmentally friendly working fluids. A steam Rankine cycle was incorporated to harness waste heat from exhaust gases and jacket water. Results demonstrate that the integrated system achieves substantial improvements in energy utilization, recovering up to 1036.82 kW of power, which represents approximately 58 % of the auxiliary engine demand, while enabling daily carbon dioxide savings of nearly 7.9 ton. Environmental analysis confirms the system's capacity to reduce fuel consumption and mitigate emissions in line with International Maritime Organization regulations. The economic evaluation highlights competitive greenhouse gas abatement costs, reinforcing the strategic role of waste energy recovery in supporting compliance with emission trading schemes. The findings provide actionable insights for ship operators seeking cost-effective pathways to improve sustainability and operational performance.