Coupled energy-transport system modelling for modernizing the Finnish Archipelago Sea ferry fleet

Diesel-powered commuter ferries operating in the Finnish Archipelago Sea are nearing the end of their technical lifespan. At the same time, Finland targets a reduction of up to 95% in greenhouse gas emissions relative to 1990 levels by 2050. These national goals, combined with tightening regulatory requirements, justify the transition to a low-emission fleet. However, the scale of investment necessitates rigorous planning to ensure economic feasibility.

Current ferry routes in the Finnish Archipelago Sea differ significantly in travel times, passenger volumes, and cargo requirements. In this theoretical study, we evaluate eleven routes individually by comparing full electric, hybrid-electric, and indirect electric alternatives (hydrogen, e-methanol) for replacing the existing diesel fleet. For each alternative, we assess supply chain aspects, including fuel road transport logistics, electricity grid limitations, and the availability and sizing of charging infrastructure.

To support quantitative investment analysis, we develop and apply a coupled energy-transport system optimization model. The model integrates route and schedule simulation, cost-optimal energy sourcing, and sizing of onboard and onshore systems. Preliminary findings show strong potential for direct electrification, with substantial reductions in operating costs and emissions. However, longer routes remain reliant on indirect electrification, increasing the carbon abatement cost when aiming for deeper emission reductions. Ongoing work continues to evaluate operational aspects (e.g., alternative schedules) and technological aspects such as local energy production and storage.