Major battery energy storage system (BESS) fires have drawn attention to the impacts of Li-ion thermal runaway
These safety incidents can be catastrophic, causing harm to on-site personnel, hazards to health and environments with the release of toxic volatile organic compounds (VOC), and large financial and asset loss. BESS developers are adopting various passive and active thermal management materials and technologies to improve the safety of their Li-ion BESS technologies.
IDTechEx’s new report “Thermal Management, Fire and Explosion Protection for BESS 2026–2036: Materials, Technologies and Players”, addresses the root causes and impacts of BESS failure, forecasting that this market will reach US$25.4bn in value by 2036.
Root causes and impacts of Li-ion BESS failure
The root cause of thermal runaway and failure in BESS can be due to poor design, manufacturing, assembly and integration, or operation of Li-ion BESS technologies. Many of the BESS incidents recorded globally suggest that integration and assembly of BESS are root causes of failure, with the balance of system (BOS) being a leading contributor. The BOS could include DC and AC wiring, HVAC subsystems, and safety elements, e.g., fire suppression systems. This was what caused the Victoria Big Battery Li-ion BESS fire, where during commissioning, a leak in the coolant system led to the fire. With the capacity of Li-ion BESS containers and grid-scale project sizes increasing, the severity of thermal runaway events, and the impacts on the BESS market, could become more severe.
BESS fires have also led to markets stagnating. For example, South Korea faced a reduced number of installed BESS technologies after many Li-ion battery fires in 2018. The financial implications of BESS fires and explosions for the BESS developer can be immense, eroding wider customer trust in the Li-ion BESS market and leading to some customers turning to safer energy storage (ES) technologies, e.g., redox flow batteries (RFB), even if these come with higher Capex.
Addressing Li-ion BESS failure and large-scale fire testing
More stringent checks during commissioning and operation of BESS and workforce training could be key methods to minimizing BESS failure, the report suggests. If BOS components are provided by third parties, then further communication between parties may be needed to ensure the entire system operates harmoniously.
Sharing knowledge of BESS failure root causes from the field could improve developer understanding and benefit the wider market, but enforcing such transparency is challenging, as it could unfairly implicate third parties such as cell or component suppliers. Although advanced sensors and battery management systems (BMS) can help identify failure mechanisms, the complexity and destructive nature of thermal runaway events can prevent precise root-cause determination. Therefore, BESS developers could focus on ensuring systems can effectively react to and contain thermal runaway, using measures like robust fire suppression and gas venting to prevent cascading failures between BESS units.
In fact, many regulations do not require multi-unit or large-scale BESS safety testing, leaving developers unaware of the potential impact of cascading fires in large, GWh-scale projects. However, in the US, the upcoming 2026 edition of NFPA 855 will begin to address this by requiring large-scale fire testing (LSFT) (installation-level test) with UL 9540A to demonstrate that BESS installations can contain thermal runaway without propagation to neighbouring units.
Some key BESS developers including Sungrow, BYD, and Huawei have started conducting large-scale fire tests. This could be a trend that spreads globally and should promote safer Li-ion BESS systems, but this will come with added costs for BESS developers.
