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4 Battery-Electric Ferry Technology and Operations
4.1 System architecture
Battery-electric ferries can be described as integrated power-electronic platforms rather than conventional mechanical drivetrains. The core elements are:
- Energy storage: Maritime-grade lithium-ion batteries (NMC, NCA, LFP) in segregated compartments. Increasing interest in lithium-titanate (LTO) chemistries for high-cycle routes due to superior cycle life and fast-charging tolerance.
- Power distribution: DC grids with multiple converters feeding propulsion drives and hotel loads. Zonal architectures providing redundancy.
- Propulsion and manoeuvring: Electric azimuth thrusters or azipull units, often with twin-end symmetry on double-ended ferries.
- Energy management: Onboard Energy Management Systems (EMS) optimise power flows, charge/discharge rates, and thermal management.
4.2 Shore charging and port integration
Shore charging hardware has moved from bespoke systems to more standardised high-power DC solutions. Automated connection methods include movable arms, pantographs, and robotic plugs. For Lavik-Oppedal, NES will deliver two onshore charging stations integrated with the autonomous ferries, designed for very high availability and consistent turnaround within about 10 minutes.
4.3 Deployment experience
- MF Ampere: In continual service since 2015, with estimated annual CO2 reductions above 2,500-2,700 tonnes. Demonstrated that battery replacement and lifecycle management must be built into the business case.
- E-ferry Ellen: Operates a 22-nm route with a large 4.3 MWh battery. Ongoing upgrade to a 3.2 MWh LTO system.
- MS Medstraum: First fully electric fast ferry (HSC Code) under the TrAM project. Uses modular design and digital twin-based optimisation.
- Candela P-12: Electric hydrofoil ferry "flies" above the water using submerged foils, cutting energy use dramatically.
These cases show that electrically propelled ferries are technically mature for routes up to at least 20-25 nm.
4.4 Safety and risk profile
Formal Safety Assessment (FSA) has been applied to battery-powered high-speed ferries. Key findings: accident frequencies for battery ferries can be comparable to conventional propulsion if specific risk controls are implemented; risk control options such as double-redundant battery rooms often have favourable cost-benefit ratios.