Battery storage fire at Dorman facility in Chandler, Arizona, managed with robotic entry

In April 2022, a fire was reported in the morning at the Dorman battery storage facility, a stand-alone, grid-connected lithium-ion battery energy storage facility of a few tens of MWh in Chandler, Arizona, United States, operated by AES. The internal sprinkler system activated automatically and continued to apply water for several days to hold battery temperatures down. Drawing on the response to a 2019 explosion at another battery storage site in the same region, in which firefighters were injured, the responding fire service adopted a defensive strategy and did not attempt direct manual entry. Three days into the incident, crews used a robot to make the first entry and assess hazardous gas conditions inside the building. Ten days after the fire started, voluntary evacuations of nearby businesses were put in place while the building was ventilated. On the eleventh day, after a period with no further smoke detected, crews shut off the sprinklers, opened the doors and used forced air to dry the building. The fire was declared out about two weeks after it began, and site management was handed back to AES on the same day. There were no injuries.

Public statements from AES at the time described the event as thermal runaway, while noting that the precise origin of the fault, whether it began within the battery system or came from an external source, would be established through a formal investigation. Public reporting at the time indicated that the investigation was expected to continue for some months. Reporting also indicated that the sprinkler system kept the event contained but did not extinguish the underlying thermal activity. No confirmed root cause is reflected in the sources used for this entry.

Lessons drawn from the publicly reported response, independent of any final root cause:

1. build prior battery storage incident findings into local fire service pre-incident plans and site emergency response plans, including a default defensive posture where explosion risk from accumulated off-gases cannot be ruled out;
2. arrange access to remote or robotic entry capability, either on site or through the responding fire service, so that internal atmospheres can be assessed before any person enters;
3. plan containment and cooling logistics for multi-day to multi-week durations, including water supply, drainage and containment of run-off, rather than a single-shift response;
4. maintain continuous gas and air quality monitoring throughout the incident and set specific protocols for the ventilation phase, when opening the enclosure can release accumulated gases;
5. agree in advance with local authorities the triggers and communication routes for evacuating or advising neighbouring occupiers, and record who authorises handback of the site to the operator;
6. confirm before commissioning that the suppression system design intent, containment rather than extinguishment, is understood by site staff and by the responding fire service, and document it in the emergency response plan.

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