One of the most important technological developments of the 21st century so far has been the increasing use of electric vehicles, such as battery-powered ships, around the world. Each year, transportation contributes around 15% of global greenhouse gas emissions.

Scientists believe that electric vehicles have already helped to temper global emissions growth significantly since 2019 because they produce close to zero carbon dioxide and other greenhouse gas emissions when they are running.

David Brooks, patent technical assistant, Mewburn Ellis LLP

While enormous attention has been given to electric cars, there is a significant need to electrify the shipping industry as well. A study by the International Maritime Organisation (IMO) found that, in 2018, global shipping emitted over 1 billion tonnes of CO2 and was responsible for over 2.5% of global greenhouse gas emissions.

Factors in battery design

Electrifying ships poses some unique challenges to manufacturers. Perhaps the most obvious of these is that ships are much bigger than cars and so require much more powerful batteries. At the same time, ship manufacturers want batteries to be as small as possible to maximise space for passengers and cargo.

As a result, most electric ships to date use lithium-ion batteries, which offer the highest energy density of commercially available batteries. Some of these batteries are enormously powerful. Ferry operator Stena Line is aiming to launch fully electric intercity ferries that each have battery capacities of 70 mWh, the equivalent of nearly 2,000 electric cars.

Indeed, the ferry industry seems to be a relatively quick adopter of electric ship technologies. P&O launched the world’s largest double-ended hybrid ferry in 2023 to serve the popular route across the English Channel from Dover, UK to Calais, France; while Danish ferry and logistics giant DFDS has plans to invest €1bn in a fleet of electric ferries for carrying passengers and freight between the UK and EU.

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Another consideration currently at the forefront of the shipping industry’s mind is reliability. The collapse of the Francis Scott Key Bridge in Baltimore in early 2024 after a collision with a container ship was caused, at least in part, by a series of power blackouts on board the vessel.

The industry is also acutely aware of the danger posed by battery-related fires and spillages.

In the same way that diesel ships need to be refuelled while at port, electric ships need to be recharged by batteries at charging stations in ports. Interestingly, port-based batteries have very different requirements to the batteries on board the ships themselves, which means the best type of batteries to use in these charging stations is often not the lithium-ion battery.

While space is always important, ports tend to be quite large, which means there is less of a need for very high-energy density batteries in order to save room. Instead, safety and performance are the top priority. Ferries usually go back and forth between destinations several times a day, and excessive time spent in port refuelling is perceived as wasted revenue potential. Therefore, it is important that the port-based batteries can charge and discharge rapidly.

The industry is also acutely aware of the danger posed by battery-related fires and spillages. A fire at a major shipping port could have huge ramifications on international shipping, while the proximity to water means that any battery leakage could pour toxic metals and other battery chemicals into the sea, with potentially significant environmental consequences.

Organic flow batteries

The industry has so far focused on organic flow batteries as the choice technology for these in-port charging stations. While organic flow batteries do not have quite the same energy density performance as lithium-ion batteries, they are more environmentally friendly because they are usually made from organic materials consisting mainly of carbon, hydrogen, nitrogen, and oxygen, rather than rare metals.

One of the most promising research areas in organic flow batteries is the use of quinones as electroactive components. Quinones are a group of naturally occurring materials used by plants for photosynthesis, which can react with protons extremely quickly and without any catalysts to form a higher-energy compound (a hydroquinone). These properties can be exploited in battery charging.

Meanwhile, another advantage of using organic materials like quinones in batteries is that, unlike metals, their chemical behaviour can be easily adjusted to fine-tune the voltage and various other properties of the battery. As a result, the latest organic flow batteries can quickly charge from zero to full and back to zero multiple times a day without significant degradation.

Patents are crucial assets for protecting new inventions and can be used as early indicators of technological developments.

Organic flow batteries also tend to use water-based electrolyte solutions and so are essentially non-flammable. As a result, these batteries carry a much lower fire risk than, for example, lithium-ion batteries, which use volatile organic solvents such as ethers and esters.

Prominent academic institutions such as Harvard University have been amongst the first to file patent applications for quinone-based flow batteries, and now hold an impressive portfolio of granted patents in this area covering most major jurisdictions.

Excitingly, interest from industry is growing quickly in this area too, with big players such as Mitsubishi, LG, and Sumitomo also having filed several new patent applications in recent years. Patents are crucial assets for protecting new inventions and can be used as early indicators of technological developments.

The outlook for battery-powered ships

As new advancements in battery technologies are made, and as governments and businesses face greater pressure to improve their environmental credentials, the gradual electrification of the shipping industry looks set to continue for years to come.

While ships and ports each present their own challenges for battery technologies, electrically powered ships are already well established in certain parts of the world, particularly ferries, whose short, regular routes provide plenty of opportunities for recharging.

It will be fascinating to see how battery technologies advance to enable even more industries to benefit from electrification. Perhaps one of the more challenging frontiers will be in international cargo shipping, which involves some of the world’s largest ships travelling long distances around the world without opportunities to refuel or recharge.

We will have to wait and see if overcoming these challenges will be smooth sailing or choppy waters for the battery industry.