Q HYBRID PROPULSION
CLEAN SILENT RUNNING
Safe and reliable battery systems will be essential for Sir David Attenborough while it works in the remote and hostile Antarctic environment
18 Lithium-ion batteries are
being used in hybrid
propulsion to boost power, reduce emissions
A new breed of vessels is being developed to meet the IMO’s Marpol target to reduce greenhouse gas emissions and comply with the cap on sulphur in fuel to 0.5% mass by mass, due to come into force in January 2020. Vessels such as workboats and offshore
and enable silent operation, explains Jayesh Vir, marine manager at battery maker Saft
support vessels need to boost power during dynamic positioning operations, and ferries are required to accelerate and decelerate quickly in order to maintain strict timetables and keep communities connected. To achieve this, such vessels typically have propulsion systems that are sized to meet maximum peak demand. Traditionally, this has meant multiple large diesel engines often operating in parallel to give instant access to boost power. However, the new generation of hybrid and electric propulsion vessels now use downsized engines and lithium-ion (Li-ion) battery systems that smooth the load by compensating for peaks and troughs. Battery systems can also support hotel
loads should there be an engine outage, thereby enhancing safety levels. By turning to hybrid propulsion, operators
can complement a diesel engine with a battery system. Once the battery has been charged in port or during normal operation, it can be deployed to overcome strong currents or windage during dynamic positioning, or to help a ferry come up to speed fast. This allows the operator to reduce the number of engines running or to downsize
them. This, in turn, reduces diesel consumption, greenhouse gas emissions, and engine run-hours. In addition, because the battery can vary its output, the captain can operate the engines at their point of peak effi ciency. As well as saving fuel, this also reduces the amount of wear and tear on the engine, leading to lower maintenance requirements and higher availability.
Diverse applications Scottish ferry company Caledonian MacBrayne is one operator that has recently turned to hybrid propulsion with the objective of saving fuel and emissions in line with the Scottish Government’s tough environmental targets for transport. The company’s roll-on, roll-off passenger ferry, MV Catriona, entered service on the Lochranza-to-Tarbert route in 2016. Fitted with an 800kWh battery system, the vessel has achieved reported savings of around 20% in fuel and CO2
emissions. The ferry can operate in battery-only or
hybrid mode in combination with a diesel generator. Its batteries are charged overnight from the shore, ensuring that there is always more than enough power to transport the maximum load of 150 passengers and 23 cars, or two HGVs, at speeds of up to nine knots. Meanwhile, the polar research vessel RRS
Sir David Attenborough, is an example that highlights the hard-working and rugged capabilities of Li-ion batteries. Rolls-Royce
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