INDUSTRIAL HAZARDS
Watch Victoria Hutchison of the Fire Protection Research Foundation explain the concepts of thermal runaway and stranded energy in lithium-ion batteries
‘Remain on High Alert’
As Felicity Ace cleanup efforts begin, safety experts urge officials to consider the possibility of stranded energy in EV batteries
BY ANGELO VERZONI
Maritime officials in charge of the cleanup of the Felicity Ace—a cargo ship whose haul of some 4,000 luxury vehicles were razed in a fire last week—have said there’s likely little left to burn on board the 650-foot-long vessel, setting the stage for vehicle removal and eventually towing the ship to a port. But experts from NFPA and the Fire Protection Research Foundation caution that the electric vehicles (EVs) on board, which were said to have contributed to the fire’s intensity and persistence for several days, now contain damaged lithium-ion batteries that could be prone reigniting days later.
“Once an electric vehicle’s battery pack has been damaged by heat from a fire or water from suppression activities, this can leave the batteries in a damaged state,” said Victoria Hutchison, a project manager at the Research Foundation. “Just because it’s damaged doesn’t mean all the energy within the battery pack is gone. This can pose delayed hazards, particularly when removing the vehicles from the vessel, and this should definitely be accounted for and monitored.”
Energy essentially remaining trapped inside batteries is a phenomenon known as stranded energy, Hutchison explained, and it’s why car fires involving EVs have been known to reignite after initially being knocked down. Because of this, Hutchison recommended that the officials in charge of the Felicity Ace cleanup “remain on high alert.” If the batteries have been allowed to “fully consume themselves” in the course of the fire, though, Hutchison added, the risk of reignition is much lower. Still, she said, officials should err on the side of caution by using thermal imaging cameras to watch for any rapid spikes in heat, keeping the vehicles away from combustible materials as they’re removed, and having a water source nearby in case of reignitions.
Brian O’Connor, an engineer at NFPA, agreed with Hutchison. “They might not be aware of the reignition hazard, and that should definitely be a priority when towing the ship to its next destination,” he said.
In 2018, after a fatal crash and fire involving a Tesla Model X in California, the car’s batteries reignited at a junkyard six days later, according to The Mercury News. Part of the challenge in incidents like this, Hutchison said, is getting water directly onto the EV battery packs, which are located in the undercarriage of the vehicle. Additionally, what she described as “copious” amounts of water are typically needed to quench the flaming batteries. When a Tesla Model S crashed and caught fire last year in Texas, firefighters used more than 30,000 gallons of water on the blaze—that’s about as much water as the average American household uses in three months.
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News of the Felicity Ace fire first made headlines late last week. Its 22 crew members were evacuated safely before the abandoned ship began drifting in the mid-Atlantic with a cloud of white smoke in its wake. After several days, the fire appeared to die down on its own. Officials now say the ship, which was originally bound for Rhode Island, will be towed to either Europe or the Bahamas.
With their airtight steel hulls and narrow passages, fires on large marine vessels are notoriously challenging incidents, feared nearly universally in the fire service. Read more about the challenges in “Close Quarters,” from the September/October 2019 issue of NFPA Journal.
ANGELO VERZONI is associate editor of NFPA Journal. Follow him on Twitter @angelo_verzoni. Top photograph: GETTY IMAGES