Battery storage fire safety: How a 2019 explosion near Phoenix led to changes in the industry

PHOENIX (InvestigateTV) — Battery energy storage system facilities are expanding across the Phoenix Valley, but fires at those sites have raised safety concerns for nearby residents and first responders.

The Environmental Protection Agency says battery fires can burn for hours and release harmful gases that pose health risks. The EPA also says a response plan is critical when managing one of these sites.

The danger inside battery storage facilities

Lithium-ion batteries store large amounts of electricity that can become unstable. They have caused fires in golf carts, garages, cars, airplanes and buildings.

Phoenix Fire Captain Michael Duffy warned the Phoenix City Council in July about the dangers posed by lithium-ion batteries and the facilities that house them.

“These batteries, when they cook off, can get to temperatures of 3,600 degrees,” Duffy said.

Battery energy storage system facilities — rows of structures resembling shipping containers filled with racks of batteries — are operated across the Valley by utilities including APS and SRP. Video from the University of Texas Fire Research Group shows how quickly a fire can ignite inside the containers and spread to other batteries and racks.

“We’re not talking about a Tesla car on the roadway,” Duffy said. “We’re talking an enclosed structure that is a maze.”

The 2019 McMicken explosion

In April 2019, a fire broke out at the APS McMicken Battery Storage Facility in Surprise. Gas seeped out of the smoldering building before firefighters approached.

“When our Peoria firefighters opened the door, they gave this monster what it needed, which was air,” Duffy said. “And it deflagrated. It exploded. It was a freight train coming out of the door.”

The explosion, described as a runaway thermal event, severely injured four firefighters, including Peoria Fire Division Chief Hunter Clare.

Clare returned to work but said he will never be cleared to work on a front-line fire truck again.

“I had to learn to walk again,” Clare said. “I only had one working extremity at the time. I’d broken my neck, my back. Amputated my feet off. I had to get those reconnected. Shattered my scapula, broke bones, lots of different things that are going on. Traumatic brain injury.”

Industry changes after McMicken

The investigation that followed the 2019 explosion resulted in major changes to how battery facilities are set up and monitored.

“Our incident showed that there needed to be some changes within the industry,” Clare said.

APS Engineering Supervisor of Renewable Generation Kasdan Hall said the utility decommissioned all sites similar to McMicken and started from scratch.

“There was a moment of reflection for us where we pulled in industry experts and said, ‘How can we learn from this and make these systems safer moving forward?’” Hall said. “We decommissioned all of the sites that were like McMicken back in 2019 and started from scratch.”

Hall showed us a solar battery site located about 60 miles southwest of Phoenix. At the new facility, battery storage units are no longer housed indoors. The site includes ventilation for explosion control, and any fire is designed to burn itself out.

“The technology is completely different,” Hall said.

Hall said the safety improvements represent a significant change for first responders.

“Basically the response is they show up, we let it smolder, let it do its thing, and then it’ll put itself out,” Hall said. “If we need additional assistance, we’ll call for it.”

Not every battery energy storage system is as updated as APS. Smaller battery systems are also present in many data centers.

First responders in Arizona said they are in a better position today to respond to an emergency at one of these facilities than they were a few years ago.