Published by the Naval Architect on January 2021. Link to the magazine can be found here.

By Brent Perry | Chief Executive Officer, Sterling PlanB

Brent Perry, CEO of battery solutions provider Sterling PlanB, on why marine decarbonisation requires sage and effective energy storage

Energy storage systems are vital for shipping to meet the decarbonisation timeframes already embedded in IMO target, as well as those to be included in the EU’s proposed Green Deal. Currently, the IMO requires a reduction in carbon intensity of at least 40% by 2030, and by 70% by 2050, compared to 2008 levels. Further, the IMO intends to reduce the sector’s total carbon emissions by 50% by 2050 compared to 2008.

This is just the beginning though, as this decarbonisation strategy will likely be revised to further increase ambition in coming years. Other regulators are set to introduce their own targets, but existing goals require immediate action by shipping companies. Not only to reduce the environmental impact of ships currently being designed and built, but also on those that are already in operation. Meeting these targets means implementing significant efficiency-boosting technologies today and preparing now for increased regulation in the future.

Weather on its own, in tandem with low or zero-carbon fuels, or in conjunction with other technologies, energy storage systems (ESS) will be key to hitting these targets. Recent rapid growth in ESS adoption saw 356 all-electric or hybrid vessels in operation or under construction last year, according to DNV GL, and the number has continued to grow during 2020. Where the majority of these are smaller craft or passenger vessels (vessels which can best take advantage of the ROI benefits of full electrification), projects such as the installation of a 600kWh ESS on the Maersk Cape Town show that the appetite and applicability for energy storage cuts across segments into larger ocean going vessels of all types.

The benefits of energy storage

Modern marine ESS’ are incredibly versatile. Available in many configurations and used for a variety of purposes, a modern battery, commonly built with lithium-ion cells, can help a vessel ensure compliance with emission regulations and can achieve operational cost savings for a wide variety of vessels.

For some ships, that means fully electric or hybrid propulsion. A recent DNV GL report for the European Maritime Safety Agency suggested that ferries could see fuel cost savings of up to 100% with a payback period of less than five years on ESS power, while they suggested that large cruise vessels could see cost savings of up to 5% from implementation of hybrid power systems. It also notes that the technology is particularly applicable to short sea shipping, dependent upon the route and operational criteria.

For larger vessels, peak shaving may be more appropriate. Current deep-sea vessels could see fuel savings of up to 14% through peak shaving, using an ESS to meet short spikes in energy demands to ensure that the vessels engines run at its optimum power settings for as long as possible. Simply reducing the need for additional generators to be brought online to meet intermittent loads can provide significant opex savings. In many of these applications, the energy from batteries is further used to power vital operational systems such as pumps, winches and carnes, or to offer hotel loads for crews that would otherwise be delivered via diesel generators.

Depending on vessel’s purpose, fuel saving are not the only issue. In some sectors, especially offshore, energy storage represents huge logistical and operational benefits by cutting risks. Risk reduction is achieved by providing instant spinning reserve, available in milliseconds from the batteries, which in turn delivers flexibility and value. In these configurations, and ESS can quickly provide immense amounts of energy, delivering back power to provide operators with vital redundancy and a time buffer if traditional equipment fails.

In other applications, an ESS could be solely used for other operational functions of vessel. This is how the system onboard the Maersk Cape Town operates and is particularly applicable to refrigerated cargo ships or those carrying refrigerated containers.

Refrigeration for these vessels requires vast amounts of variable power, changing based on the differential between the temperatures set by cooling systems and ambient temperatures. This has historically been delivered solely through onboard generators, which exposes owners to both high supplemental fuel costs and significant risk in the case of failure. Employing an ESS to provide peak shaving power and backup redundancy in this context has a huge benefit in actual cost reduction and risk mitigation.

These benefits are expected to become more pronounced as new zero-carbon fuels have lower energy densities than vessels are currently used to, providing smart support through energy storage will be more operationally important than ever. Biofuels, hydrogen or ammonia all benefit from additional power to augment heavy machinery starts or other intermittent loads. In the future, al commercial vessels will have a battery room and those which implement energy storage today will see the greatest cost savings and strategic advantage going forward.

However, as with any major maritime innovation, good design is critical for ensuring both safety and effectiveness. This design must encompass the whole of an ESS, as well as its surroundings and integration into other systems, from the start.

Holistic design unlocks the potential of energy storage

Good design is more than just designing powerful il-ion cells. Good design must cover the entirety of the space around those cells and the ESS itself, to ensure efficiency and safety.

Li-ion cells’ unique properties confer significant benefits over any alternative, but if poorly managed, they come with significant risk. Risk of thermal runaway is significant in that it is a rarely occurring event but can be catastrophic if it does happen. It starts when a damaged or faulty cell overheats, causing an exothermic reaction in adjacent cells, cascading through the entire battery. As these cells degrade, they emit highly flammable and toxic gasses. Without proper system in place, this chain reaction that could lead to fire or in the worst case, explosion.

Simply put, all ESS require active cell cooling. Active cooling is most commonly derived from the circulation of a chilled liquid coolant through passages surrounding the cells. Liquid cooling, when integrated fully into the design of a system, ensures that the entirety of the cell is kept at a uniform temperature. Working in conjunction with thermal barriers between blocks of cells, the Sterling PlanB CellCool system has been designed to cool the very core of each module and every cell in the system. CellCool is so effective at removing thermal energy that it can cool the cells faster than they produce heat in a thermal runway type incident. This robust cooling has been third-party validated to prevent and even reverse thermal runaway after it has started. Until now, this effectiveness of cooling was unheard of in the lithium battery industry.

Uniform cooling also eliminates hotspots within cells that could cause accelerated ageing, or failure in the first place. Further, this level of constant, uninterrupted cooling provides increased performance capability and enables the ESS to run at an average continuous rate of 300% – allowing a 1MWh battery to provide 3MW of power for machine starts or any other intermittent loads.

Yet, even when taking these precautions, the risk of thermal runaway can be reduced, but never fully eliminated by any system. That is why explosion-proof, fully integrated venting systems are required to move toxic, flammable gasses from the battery to the outside of the vessel. Sterling PlanB’s patented and integrated ventilation system, E-Vent, vents the core of the battery, meaning the battery room is kept clear of fumes. This in turn reduces fire and explosion risk and allows safety or maintenance crews to re-enter the affected area sooner than if the area was filled with toxic and flammable gasses. Similarly, control electronics such as cooling pumps and alarms must be fully integrated into the vessel’s electrical infrastructure to make sure that all systems work together seamlessly – and cannot be unintentionally disabled by well-meaning crew.

Decarbonisation is already happening in the maritime industry and energy storage is key to enabling a painless transition for many vessel types. By future-proofing their fleets today using a product that provides rapid ROI, shipowners position themselves to have the advantage over their competition the coming years. However not all energy storage systems are equal, and it is critical that systems provided to the commercial marine industry are designed to deliver the quality, value, safety, and high level support that shipowners deserve and expect.