Beijing rooftop battery storage explosion during firefighting, two firefighter fatalities

What happened

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.

Contributing factors

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 learned

1. Battery storage sites require exclusion zones around all sections, not only the visibly affected area, because an explosion can occur in an adjacent section during response.
2. Fixed detection and ventilation must be designed for thermal runaway in lithium iron phosphate systems, as portable equipment proved insufficient.

More lessons on spacing, layout and fire spread, detection and monitoring, from every incident on the register.

Not yet known

• Battery system model and age
• Cost of damage and downtime
• Exact thermal runaway trigger

This entry is updated when these are reported. Get an alert for the next one like it.

Source

ctif.org