ICS says batteries will need to work in hybrid systems. File Image / Pixabay

The International Chamber of Shipping (ICS) says batteries are unlikely to replace conventional fuels as the main propulsion source for large oceangoing vessels because of their low energy density.

Batteries are already being used as primary propulsion on some ferries, tugboats and short-sea vessels, where ships can recharge frequently and operate on relatively short routes, it said in a statement on its website yesterday.

However, the technology faces a much bigger challenge in deep-sea shipping, where vessels need to carry enough energy to operate continuously for days or weeks.

Battery energy density remains far below that of marine fuels, meaning a large battery installation would add significant weight and take up valuable space that could otherwise be used for cargo.

“Battery energy density remains far too low for primary propulsion on large deep-sea vessels,” Andrea d’Ambra, ship design manager for Grimaldi Group, explained. 

“Providing sufficient energy for even one or two days of navigation would require such a large number of batteries that a significant proportion of the vessel’s cargo capacity would be lost.”

“The challenge becomes even greater for voyages lasting several days or weeks.”

Torsten Büssow, Director of Electrical & Power Systems Business at Wärtsilä Marine, said a vessel using 10 MW of propulsion power for four weeks would require close to 7,000 MWh of energy.

With current battery technology, that would translate into tens of thousands of tonnes of batteries, he said.

Instead, batteries could have a role in hybrid systems on oceangoing ships, supporting peak shaving, load optimisation, emergency power and limited zero-emission operations.

Batteries can also help reduce fuel consumption and engine running hours, particularly when combined with alternative fuels and shore power.

Charging infrastructure is another hurdle. Large vessels would require high-capacity shore connections without increasing port turnaround times, putting additional pressure on ports and electricity grids.

The ICS therefore sees batteries as one part of a broader decarbonisation strategy, rather than a standalone replacement for marine fuels on long-haul voyages.