The rise of electric and hybrid energy propulsion systems necessitates improved guidelines on gas detection and better fire suppression techniques for lithium batteries
At the start of 2020, three containers on the 2008-built, 10,800 TEU containership Cosco Pacific combusted creating the seafarers’ worse nightmare – a fire at sea. The initial investigation found that the containers were filled with lithium batteries and should have been stowed separately. However, the shipper had falsely declared the batteries as ‘spare parts and machinery’. The incident highlights the inherent dangers associated with lithium battery technology, which is now being applied to electric and hybrid propulsion systems.
Therefore, a new report from class society DNV GL on large-scale batteries on ships and dealing with fires is very timely. The report, “Maritime Battery Safety Joint Development Project: Technical Reference for Li-ion Battery Explosion Risk and Fire Suppression” was produced by DNV GL in collaboration with the Norwegian, Danish and US maritime authorities, battery manufacturers, system integrators, suppliers of fire extinguishing systems, shipyards and shipowners. In the report, the collaborators assess explosion and fire risks in maritime battery installations and the effectiveness of fire extinguishing systems in the event of a battery fire.
Batteries can produce very hot fires, coupled with the risk of explosion. DNV GL’s report presents the results of research on what happens during a fire in a battery compartment, the release of gases, and the usefulness of various extinguishing systems in combatting the fire and preventing explosions. One of the most important findings concerns ventilation systems, which are critical to avoiding an accumulation of explosive gas. However, the report concludes that ventilation alone will not adequately mitigate gas accumulation if a significant portion of the battery system ignites.
Regarding fire suppression, direct injection of foam offers the best heat mitigating performance*. The report notes: “High pressure water mist protection provides good heat mitigation at module level in addition to providing full battery space protection from external fires. It also has good gas absorption and gas temperature reduction capabilities.”
Interestingly, the report also notes that Novec has some negative properties: “Novec extinguishes the battery fire flames, but performs poorer [as] regards to heat mitigation, gas temperature reduction and gas absorption compared to water mist. Room ventilation needs to be closed for this suppression method to be functional. This can increase the toxic and explosive battery gas concentration in the room until ventilation can start again.”
The gasses identified in this project are carbon monoxide, nitrogen dioxide, hydrogen chloride, hydrogen fluoride, hydrogen cyanide, benzene and toluene. Launched in 2017, the research project draws on the experience of a wide range of maritime stakeholders. “It is very important for us to work closely with all parts of the industry and understand the full picture as we work to promote safety in our regulatory development work,” said Danish Maritime Authority’s senior ship surveyor Denis Cederholm-Larsen.
* The fire suppression liquids are much colder than the battery fire, and the aim is to rapidly cool the batteries to below the reaction temperature.