Li-ion battery technology can offer a number of key advantages for designers in the marine industry including : high-power and/or energy storage in a compact space and weight-saving package, high-efficiency, long calendar and cycle life – even when operating in extreme temperatures, zero-maintenance requirements. Saft anticipates that Li-ion technology will be of particular interest for hybrid propulsion systems in which the batteries work in conjunction with diesel (or possibly gas turbine) generators and electric motors. The specific advantages of this hybrid power approach will vary according to the type of application:
Work boats
Hybrid power could offer significant improvements in fuel efficiency and CO2 savings for work boats that spend most of their time at sea moving into position and only operate at full power for very short periods. So rather than sizing a diesel engine for peak power it can be specified at a more economical size for average power, with the extra power drawn from the batteries when required. One particular target is tug boats where in a hybrid configuration a battery system operates in parallel for low power operation, and is then combined together with a significant boost from a single diesel generator for infrequent high power operations. There is also scope for load-levelling type applications (similar to diesel-electric trains) in which the diesel generator is maintained at a constant load – typically 80% of capacity – saving fuel, cutting CO2 emissions and reducing maintenance.
Passenger ships
Hybrid or full electric mode could be an attractive option for passenger ferries and shuttles that spend much of their operational life in harbour for docking and undocking. Switching to clean electric power when in harbour could save considerable CO2 emissions, helping port authorities to meet their environmental targets; it also offers much quieter operation that will reduce the impact on the local community.
Leisure boats
In leisure boats, such as yachts, a hybrid system will enable the vessel to switch to battery power for silent, low-speed running when entering harbour, helping to meet the growing demand from port authorities to reduce CO2 emissions. The battery could also support hotel loads when the yacht is moored, providing a green, quiet and vibration-free alternative to running diesel-generators, especially when waiting for access to harbour power points.