Beijing rooftop battery storage explosion during firefighting, two firefighter fatalities

In April 2021 a fire was reported at approximately 12:17 local time in a 25 MWh lithium iron phosphate battery energy storage system installed on the rooftop of a commercial premises in Beijing, China. The system formed part of an integrated solar, storage and charging facility comprising rooftop solar PV of approximately 1.4 MW, the battery system and electric vehicle charging infrastructure, commissioned in 2019. The response was substantial, with reports of 235 firefighters from 15 fire stations attending with 47 appliances. While responders were addressing the fire in the southern section of the battery system, an explosion occurred at approximately 14:15 in the northern section. Two firefighters were killed and one was injured. A member of staff of the system operator was also reported missing. The fire was declared extinguished at approximately 23:40 the same day, with cooling operations continuing afterwards. It remains one of the most serious publicly documented battery storage incidents in terms of human consequence. The investigation report produced by the local fire authority was subsequently translated into English and published by an international fire service body.

The fire authority investigation report stated that the precise initiating cause could not be definitively determined from the available information. The report identified several potential contributing factors warranting investigation: (1) battery cell quality, noting that the relationship between cell quality and the initiating event could not be conclusively established; (2) limitations of the battery management system relative to actual operating conditions; (3) the electrical topology of the system; (4) the performance of early warning, monitoring and firefighting systems; (5) external environmental factors, including the effect of dust storms on outdoor equipment; (6) wiring arrangement within the system. The report concluded that the explosion mechanism was thermal failure of batteries under extreme conditions involving combined internal and external influences, but that the available evidence did not allow a determination of whether the initiating event was cell quality, operation beyond cell limits, or another factor.

Lessons drawn from the official report and its published commentary:

1. build defensive tactics into pre-incident plans for battery storage, protecting exposures and allowing a controlled burn rather than making aggressive entry, because accumulated flammable gas can explode without further warning;
2. treat every part of a battery installation as hazardous during an incident, not only the section that is visibly burning, and set exclusion zones that account for adjacent enclosures or sections;
3. confirm during design and commissioning that fixed detection, ventilation and suppression provisions are adequate for a thermal runaway event, and do not rely on portable or handheld extinguishing equipment for the emergency response;
4. assess compound failure modes where solar generation, storage and charging infrastructure share a site, including energy sources that remain live during an incident, and reflect these in fire service familiarisation and training;
5. provide the fire service in advance with site layout drawings, isolation procedures, gas and thermal monitoring points and agreed pre-incident plans, so that layout is not being learned during the response;
6. publish or share investigation findings after serious events, including translation where the audience is international, so that other operators can act on the same evidence;
7. do not assume that lithium iron phosphate chemistry removes the need for explosion protection and defensive tactics, as this event involved that chemistry.

ctif.org/news/accident-analysis-beijing-lithium-battery-explosion...