By
Johan Roos |
Over the past decade, the number of fires occurring on the decks of ro-ro ferries has been closely monitored by Interferry, the shipping association representing the global ferry industry.
In most cases, the fires have been attributed to an electrical fault, often a malfunctioning reefer unit. However, the industry has raised concerns over how best to manage fires emanating from the lithium-ion (Li-ion) battery-powered electric vehicles (BEVs) that are gradually replacing the classic petrol and diesel-powered vehicles (ICEVs) carried onboard ro-ro ferries. Questions have also been asked about the efficacy of a fixed water-based extinguishing system (drencher system) in relation to Li-ion battery fires.
Between September 2019 and August 2023, Interferry collaborated with other members of LASH FIRE, a European Union-led research project, to develop and validate effective operational and design solutions to significantly reduce the risk of BEV fires onboard ro-ro ships. As part of this project, LASH FIRE has performed tests comparing the fire suppression performance of a drencher system for both ICEV and BEV fires.
Relative to the total number of vehicles, the number of BEV fires is lower than ICEV fires. Even so, stringent measures related to the carriage of BEVs have been discussed, including everything from installing additional firefighting capabilities, to segregating BEVs onboard or prohibiting BEVs on ro-ro decks. This is because several factors make it very difficult to extinguish a fire within a battery pack.
First, the plastic housing of the battery pack acts as a shield for the extinguishing agent (for example water), and secondly, the battery pack will also be shielded by the vehicle’s body. Plus, the chemical components within the battery cells provide a high-density energy source to sustain the fire locally. This shielding effect is mostly relevant if the fire starts in the BEV’s battery, which is typically caused by a short circuit leading to a so-called thermal runaway. When the fire does not originate in the battery, the suppression activities will hinder its spread and significantly reduce the risk of a thermal runaway.
A BEV may also end up on fire when stowed adjacent to a vehicle that catches on fire, but in this scenario the consequences are no worse than if it were a petrol or diesel car by virtue of the unlikeliness of the BEV’s battery experiencing a thermal runaway. In fact, a non-battery-related fire in a BEV will likely release less heat than one involving liquid fuel in a tank because a plastic fuel tank will catch fire much faster than a Li-ion battery.
LASH FIRE carried out a series of tests comparing the fire suppression performance of a drencher system for fires involving ICEVs and BEVs, respectively. The tests simulated a ro-ro space with a five-metre-high ceiling and a fire suppression system designed in line with International Maritime Organization’s revised guidelines for the design and approval of fixed water-based firefighting systems for ro-ro and special category spaces (MSC. 1/Circ. 1430/Rev. 2).
Representative of today’s modern vehicles, LASH FIRE used two pairs of geometrically similar SUV-type ICEVs and BEVs during the tests. The tests illustrated that while both vehicles presented different fire scenarios, the performance requirements for existing drencher systems on both closed and open ro-ro decks meant they were sufficient to contain a BEV fire, at least to a level equivalent of an ICEV fire.
A fire caused by a fuel spill from an ICEV develops very rapidly, peaks high but burns out fast, whilst a fire starting in the battery pack of a BEV is slower and smaller (resulting in a lower heat release), but it burns longer. The scenario of the fire in other combustibles – such as tyres, exterior and undercarriage plastic parts, and the inside of the car – is similar. As the drencher system was capable of containing the fire, the tests clearly illustrated that the overall risk of carrying BEV vehicles should be considered equivalent or lower than carrying ICEVs. As for the latter vehicle type, there is the additional risk of the fire spreading horizontally if a fuel tank ruptures, sending burning fuel under the adjacent cars.
It is also important to remember that the main purpose of firefighting systems on ro-pax ferries is not necessarily to extinguish a fire but rather to contain it until the vessel can get to a port. Here, passengers are evacuated and professional firefighters board to extinguish the fire. Ferry operators should adopt a similar mindset regarding BEV fires – it is no different to what the industry has done so far, providing they release the right drencher section in time. If they are too slow and do things incorrectly, they risk spreading a fire that could result in a nightmare scenario.
In conclusion, BEVs are no more hazardous than ICEVs, yet the risks of Li-ion batteries differ to those of conventional fuels. For this reason, Interferry has recommended its members do not make any special provisions for carrying BEVs – and even charge them if that’s an option – provided that equipment and training are compliant with Safety Of Life At Sea requirements and International Safety Management code, which, of course, they always have to be!
Johan Roos is director of regulatory affairs at Interferry.
This article was first published in the Autumn/Winter 2023 issue of Cruise & Ferry Review. All information was correct at the time of printing, but may since have changed. Subscribe to Cruise & Ferry Review for FREE to get the next issue delivered directly to your inbox or your door.