Multi-aspect assessment for the retrofitting of operating vessels in ports by using advanced power systems

• Energy, environmental, economic, technical analyses of power systems are performed. • Eight different alternative power system solutions are investigated. • Power system solutions are integrated to support the operation of vessels in ports. • The feasibility of hydrogen, methanol, and ammonia onboard a tugboat is studied. • Well-to-wake GHG emissions for different power systems are evaluated. This study explores the feasibility of replacing conventional power systems with clean alternatives on a tugboat, evaluating the role of port-operating vessels as catalysts for decarbonizing the maritime sector. A zero-emission propulsion retrofitting process was assessed using advanced power systems, including fuel cell technology (proton exchange membrane fuel cell (PEMFC), solid oxide fuel cell (SOFC)), internal combustion engine (ICE) powered by sustainable fuels, and battery (BAT) system. The analysis integrates considerations of energy consumption, technical viability, economic feasibility, uncertainty factors, and environmental performance, offering a holistic evaluation of various power system solutions. The results indicate that the full BAT system demonstrates the highest energy efficiency by minimizing primary energy consumption. Hybrid systems by integrating BAT with methanol-ICE or PEMFC provide substantial energy savings and exhibit superior technical feasibility due to their reduced weight, and volume compared to other solutions. Although systems based on hydrogen ICE and SOFC exceed the available engine room volume, they may still be viable with the use of deck space. Economically, hybrid systems outperform standalone systems, with the PEMFC-BAT system emerging as the most cost-effective option due to its low cost. Environmentally, the full battery system achieves the greatest reduction in emissions when powered by renewable electricity, while the hybrid system between SOFC and ICE demonstrates notable environmental benefits under grid-electricity constraints. The PEMFC-BAT system, under different weighting scenarios, is the optimal solution for tugboat retrofitting, with the full BAT system as a strong secondary option, providing a clear pathway for decision-making in the retrofitting process.