Techno-Economic Evaluation of Diesel and Hybrid Propulsion Systems for Tugboats at Ports

The maritime sector, while essential for global trade, is a significant source of greenhouse gas emissions, creating an urgent need for cleaner propulsion technologies. This paper compares the technical and economic performances of diesel mechanical propulsion systems and hybrid propulsion systems in tugboat operations at Maltese ports. Using measured generator load datasets, the results showed that HPS reduces the annual fuel consumption by 14% from 252 to 216 tons. This leads to a corresponding 112-tons reduction in CO₂ emissions, from 796 tons to 684 tons. Economic analysis showed that HPS achieves annual operational cost savings of €22,104, representing a 10.3% cost reduction compared to DMPS driven by reduced diesel fuel consumption and strategic use of onboard battery power, even when accounting for unsubsidized electricity costs for charging onboard battery banks. These results demonstrate that HPS is a sustainable and cost-effective alternative, supporting global decarbonization goals and compliance with local environmental standards. This paper also estimates the capital investment for hybrid adoption, discusses battery lifecycle considerations, and evaluates the broader applicability of the findings across maritime environments.