Decarbonisation, efficiency & safety: the case for energy storage post-MEPC 76

Decarbonisation, efficiency & safety: the case for energy storage post-MEPC 76
Paul Hughes, president of Sterling PlanB

What role do batteries have in shipping’s transition to a low carbon future? Industry’s initial steps to comply with the IMO’s latest decarbonisation strategy indicate that much of the global fleet is planning to de-rate engines, writes Paul Hughes, president of Sterling PlanB.

According to Matthew Williams of Lloyds Register, “overridable power limitation (OPL)—also referred to as engine power limitation (EPL)—is expected to be the lowest capital cost, least invasive means of compliance for the majority of ship types to comply[1].”

So, what role do batteries and energy storage have to play in shipping’s energy transition, when so many shipowners plan to simply slow down? What is the case for investing in energy storage systems (ESS) if limiting engine power is the simplest and quickest fix?

Batteries occupy a complex place in the decarbonisation landscape. While, like fuels, they store energy, they can’t be considered a full replacement for fossil fuels for all ship types. However, they still have an important place on virtually any ship in the future fleet. From reducing emissions to minimising maintenance costs and increasing safety, it’s likely that most ships in the coming years will benefit from ESS solutions in some shape or form.

Electrification and the decarbonisation challenge

The original—and continued—strongest rationale for ESS installation is to reduce dependency on fossil fuels. This doesn’t change in the new landscape, even if owners adopt slow steaming as a compliance strategy. Bud Darr of MSC recently outlined this case; “The less of the fuel that you need for the level of autonomy that you have to have for a ship, the shallower those hills are that you have to climb with those alternative fuels. You are bringing more of them into reality sooner by continuing the drive for energy efficiency[2].”

Reducing reliance on fossil fuels will still be valuable for ships adopting slow steaming. Low carbon fuels will likely be expensive, at least initially, and vessels with some form of additional battery or hybrid power may be able to maintain higher speeds than the competition.

The ferry segment is where we see the most benefit from ESS in hybrid solutions. More frequent, shorter journeys means that ferries have ready access to shore power for recharging, and a greater need to power hotel loads without using generators. Additionally, due to their closer proximity to highly populated and inhabited areas, there’s an immediate need to reduce emissions and particulate matter to protect public health. And because of the slower speeds at which ferries, and other smaller vessels often travel, battery propulsion can act as a central fuel source to replace diesel.

Data from a recent project shows that a vessel operating on a high frequency route of some 23 sailings a day could save significantly on fuel consumption due to charging while the ferry is docked. This reduced fuel use equates to approximately 150kg of fuel per trip, or, an estimated US$540,000 in fuel savings per year.

Beyond fuel savings

Furthermore, this project shows that ESS systems delivered additional lifecycle benefits. Cost savings are key to the battery propulsion picture. By using ESS to support generator power, or using the generator to charge batteries, the solution helps generators maintain an optimum load of around 85-90 per cent, reducing the need for maintenance and saving an additional estimated US$400,000 per annum on this particular project.

These benefits can be enhanced when systems are designed around the needs of shipboard operations. Sterling PlanB has, for instance, designed a long lifecycle solution, in which batteries are switched out every five years. This saves weight and space as it allows a smaller battery to be installed, without needing to compensate for degradation over time, and allows vessels to benefit sooner from advances in battery technology, which is still evolving quickly. The cells can also be recycled or go on to enjoy a more relaxing “retirement,” serving as energy storage on land for use where they can still perform a useful role, but have lower performance requirements, prolonging their lifespan.

Full-scale solutions

But what about deep-sea vessels? This is where we see the value of ESS stretch beyond their decarbonisation benefits. ESS and battery power systems are unique in their ability to deliver high volumes of energy on demand. While the majority of maritime engines are designed to operate with a stable load, ESS can balance this out. This is invaluable in a variety of situations where it would otherwise require a lot of extra fuel, or put a strain on the vessel’s systems to supply the power needed.

This is a contributing factor to ESS’s growing adoption as “backup” energy sources. In recent months and years, the shipping industry has seen increasing container losses, many of which have been involved vessels experiencing loss of power, either completely or in part. After a blackout, steering control is significantly compromised, and the emergency generators can take at least 45 seconds to start back up, during which time external elements are in control of the vessel.

The risk here—both to cargo and crew safety—is immense, and certainly requires a higher solution to help mitigate that. This is where ESS is being implemented more specifically in the sector, enabling operators and masters to retain control in the event of a blackout or other potentially dangerous event, bridging the gap until power is restored. And the need to enhance safety at sea is a high priority in the ESS sector.

The question of ESS safety

Despite rapid innovation and advancements in ESS technology, we have seen an increase in incidents involving batteries. On October 11, 2019, for example, an explosion rocked passenger ferry Ytterøyningen while dockside at Sydnes, Norway. The vessel, recently refit with a lithium-ion battery hybrid drive, is part of the new fleet of low- and zero-emission vessels being deployed across Norway and other parts of the world. The vessel was at dock, having been pulled from service the night before due to a fire in the lithium propulsion batteries; a condition known as thermal runaway. Similar incidents in recent months suggest that, in a rush to create the market for ESS solutions, suppliers are engaging in a dangerous “race to the bottom” on safety.

The most prominent safety issue is thermal runaway. Thermal runaway can occur when battery cells are subjected to mechanical damage or operating over, or under, the correct voltage or internal temperature. In these situations, heat may be generated within the lithium-ion cells which results in the temperature increasing until the cell vents toxic and flammable gasses. Fires can also propagate to other cells, resulting in catastrophic damage and danger to crew, passengers and vessel health. If an event such as this occurs while a vessel is at sea, the risks are proportionately greater.

Thermal runaway may be a leading and very serious issue, but it is a preventable one. In fact, thermal runaway is oftentimes a result of manufacturers’ lack of transparency surrounding safety issues and operators’ lack of informed training and use.

Solving the safety equation

When impacted by thermal runaway, lithium-ion batteries can reach temperatures in excess of 900°C, making the establishment of strict measures imperative. DNV’s new 2020 class rules for commercial vessel batteries support this. Earlier this year, Sterling PlanB secured this revised certification, adding the standard to their range of mitigating measures developed and enhanced to prevent thermal runaway. Our first line of defence against thermal runaway is liquid cooling. Sterling PlanB has always maintained that cell level liquid cooling is the only way to ensure absolute safety. Liquid cooling has been proven to be far more efficient than air cooling, which requires 3,500 times more air flow volume than water flow volume to achieve the same heat removal.

At the same time, our integrated sealed ventilation system vents flammable gases in any kind of emergency to prevent a dangerous build-up and reduce the risk of battery explosions. Our ThermalStop technology also creates barriers between fuel cells, mitigating the propagation of thermal runaway.


The maritime sector is at a turning point in its history—it is an industry facing a slew of challenges, many of which have adjacent and overlapping supporting solutions. Proving it’s no one trick pony, battery technology is set to steer the direction in which shipping travels, increasing the performance of operations, and reducing its footprint through hybrid and fully electrical solutions—something that is only expected to grow.

Yet, without greater focus on safety and safety standards, and a commitment to increased safety measures, this pursuit may only incur more cost—in more ways than one. Energy Storage Systems must be engineered to the highest standards of performance and safety, and address the need for cost-effective, long-term solutions to shipping’s decarbonisation efforts. The requirement for suppliers to embrace transparency and for vessel owners to demand the highest standards in safety remains key to ensuring the full potential of ESS and battery technology are realised.