Assessment of the risks posed by thermal runaway within marine Li-ion battery energy storage systems - considering past incidents, current guidelines and future mitigation measures

Li-ion batteries up to the MWh capacity are increasingly adopted in marine applications, wherein the fire, explosion and toxicity hazards of thermal runaway (TR) events present a unique and complex problem relative to other applications. As such, to perform a critical risk assessment of these hazards this work analyses past incidents. Short circuits related to water ingress and coolant leakage have been the most prominent cause of TR while the majority of TR incidents led to fire or explosion. HAZID analysis was carried out on the battery system, the battery space and the electronic system. Risks were significantly reduced by considering transferable technologies (from automotive and stationary storage sectors) and future technologies. Bow-tie analysis was used to assess the barriers along the threat-consequence pathways of an electrical abuse event leading to the TR hazard and a TR event leading to the battery space failure hazard. The analysis showed that the consequences of battery TR significantly increase if it leads to battery space failure as complete loss of capability, dangers to passengers, and complete ship loss can occur. Further quantitative assessment of proposed improvements is required to determine their effectiveness in hazard reduction for ongoing safety developments.