Battery-powered ships: Moving from the drawing board to the seas

Authored by AXA XL Hull Practicee Leader, Asia, Woei Chi Tan

Most of the approximately 60,000 merchant ships afloat today consume heavy diesel oil and generate carbon dioxide, sulfur dioxide, nitrous oxide, soot and fine dust. Consequently, the effects of these emissions on global climate change and public health are significant.

According to the International Maritime Organisation (IMO), the shipping industry is responsible for three percent of global CO2 emissions, more than Germany emits. This sector also accounts for about 15 percent of the nitrous oxide and 13 percent of the sulphur dioxide in the atmosphere, contributing to increased incidences of lung cancer, cardiovascular disease, asthma and other respiratory ailments.

Moreover, the IMO reports that if no action is taken, total emissions from shipping could grow 130 percent by 2050. Similarly, a study by the European Parliament found that without significant reductions in diesel fuel usage, maritime traffic will be responsible for almost one-fifth of global CO2 emissions by 2050.

Singapore’s harbour fleet welcomes new battery-powered vessels

Historically, the maritime shipping industry has been slow to change. Nonetheless, change is in the offing, driven by technological advances and new regulatory requirements.

For example, about three thousand people travel 5.5 km daily between mainland Singapore and Pulau Bukom, a small island that houses one of the region’s largest oil refineries. Previously, their journey to this facility was made via diesel-powered ferries. Now, employees, contractors and visitors travel back and forth to Pulau Bukom on one of three fully electric passenger ferries launched this year. These ferries travel at 21 knots, or nearly 40km per hour, and have battery capacities twice that of most electric ferries this size; hence, they emit significantly less carbon dioxide and no nitrogen and sulphur oxides.

In addition to these fully electric ferries, two hybrid bunker tankers also started operating this year in Singapore, the world’s largest bunker port. (Bunkers are small tankers used to transport fuels and lubricants to vessels at sea, sidestepping the need to berth ships in increasingly congested ports.)

The bunkers are outfitted with hybrid power systems comprising lithium-ion batteries and a highly automated power management system that optimises fuel-oil consumption and reduces emissions. The batteries can be recharged during periods of low power consumption and provide additional power during high consumption periods. This allows the main generators to operate with a more stable load, contributing to lower emissions.

These new ships were commissioned in response to Maritime and Port Authority of Singapore (MPA)’s requirement that all new harbour vessels—e.g., passenger ferries, tugboats and pleasure craft—be net zero by 2030. They also exemplify different use cases for successfully reducing environmental and public health impacts by incorporating lithium-ion batteries into ship designs.

A variety of applications are possible

Battery technology has advanced significantly in the last decade, mainly due to new developments pioneered by the automotive and consumer electronics industries. As one observer noted, “The lithium-ion chemistry found in (an electric vehicle) or smartphone battery is similar to that on an electric ferry”. Thus, this multi-sector engagement is driving down the cost of lithium-ion batteries and making the technology increasingly attractive and accessible to other industries.

However, the demands of maritime applications are different from those in the automotive and consumer arenas. With consumer electronics, the priorities are optimising the energy density and capacity. Ships, on the other hand, require enormous amounts of power, so the focus for ship batteries is on performance and an optimal life cycle; the latter because high-performance requirements can easily shorten battery lifetime.

As the examples from Singapore show, fully electric systems are best suited to ships plying shorter distances, including passenger ferries, offshore supply vessels and pleasure craft. For other types—cruise ships, bunkers and cargo carriers—lithium-ion batteries can be used as backup power or to run such onboard operations as heating/cooling systems or navigational controls.

Using lithium-ion batteries as backup power can also enable ships to comply with increasingly strict port requirements and travel in environmentally controlled areas. For example, in response to pressure from local communities, the operator of a passenger ferry in Sweden commissioned a ship able to sail into port under battery power alone, with zero emissions and zero noise.

Finally, although using batteries to power today’s humongous container ships isn’t feasible, some observers have speculated that batteries could play a part in reinvigorating local ports and reconfiguring global supply chains. The envisioned scenario is a return to a denser hub-and-spoke system where smaller vessels transport goods between ports that lie within the range of battery-powered ships. This could have two benefits: reversing the trend affecting smaller ports that can’t handle today’s supersized container ships and giving cargo owners more options to circumvent increasingly frequent delays at major container ports.

New risks and operational challenges

The benefits and opportunities notwithstanding, introducing lithium-ion batteries into the maritime ecosystem brings new risks. Several operational challenges must also be addressed before battery-powered vessels—either fully electric or hybrid systems—can be deployed more widely.*

The primary safety issue with lithium-ion batteries is “thermal runaway”, which occurs when a battery is subject to high temperatures, either from a high rate of current discharge or proximity to external heat sources. As the name implies, thermal runaway can cause a chain reaction, leading to large-scale fires that can damage vessels and threaten crew.

This risk can be minimised by housing the batteries in areas away from external heat sources and by providing adequate ventilation. New battery management systems (BMS) can also reduce the risks by monitoring the voltage, current and temperature of battery packs and sub-packs. Besides providing critical safety information, BMS enables ship operators to optimise energy use and availability and to increase battery lifetimes.

Integrating lithium-ion batteries into ships, either as primary or backup power sources, presents operational challenges for the surveyors and shipyards tasked with assessing ventilation systems, hazardous areas and energy-storage-system spaces; their job is to ensure that ships can sail safely. This is a new area of focus for AXA XL’s marine risk consultants, who are working closely with different experts to identify the risks and the options for minimising them.

Creating the infrastructure to recharge ship batteries represents another operational challenge. One approach is to use modular battery packs that can be easily swapped in and out so spent batteries can be recharged in onshore charging stations. Another way is to construct portside charging stations akin to those used for electric vehicles. Singapore’s MPA, for example, is working with the owner of the battery-powered ferries to make those charging facilities available to other electric harbour vessels in the future. That company is also exploring expanding its on-shore charging infrastructure on the island of Pulau Bukom.

As noted, the maritime shipping industry comprises around 60,000 ships. In 2020, fewer than 500 battery-powered ships were in operation or under construction (more recent figures aren’t available). In other words, only a handful of the global fleet is battery-powered.

Nonetheless, as battery costs continue to decline, their performance improves and regulations stiffen—a process compelled by the urgent need to decarbonise the shipping sector—more and more battery-powered ships will come online. Although the transformation will likely be incremental, AXA XL’s marine underwriters and risk consultants stand ready to support the maritime shipping industry’s ongoing efforts to reduce carbon dioxide and harmful gas emissions.

*There are also significant safety/risk management issues associated with transporting electric vehicles, consumer electronic devices, e-bikes, etc., on ships. AXA XL’s Risk Consultants are preparing guidance for ship owners/operators on minimising these risks, and their key recommendations will be described in an upcoming Fast Fast Forward article.