Explainer: Is the planned Santa Cruz County battery storage facility safer than Moss Landing?

In the shadow of January’s Moss Landing battery plant fire that forced evacuations and sent plumes of toxic smoke into the air, battery anxiety has begun to set in for Santa Cruz County residents, who have become increasingly charged around a similarly sized facility eyed for a plot of agricultural land just 13 miles north, near Watsonville.  

As it stands today, the $200 million proposal for the South County battery storage facility remains a distant vision. The developer, Massachusetts-based New Leaf Energy, still hasn’t completed its application for the project — which it’s calling “Seahawk” — and, absent a firm timeline, county officials this week said any decision on that project is “likely up to two years away.” At 200 megawatts, the Seahawk system could, when fully charged, power up to 200,000 homes for four hours. The burned Moss Landing facility, owned by Texas-based Vistra Corp., held 300 megawatts’ worth of battery storage. 

MOSS LANDING FIRE: Read Lookout’s ongoing coverage here

Although long viewed as the innocuous key to a carbon-neutral future, battery storage now faces a strengthening swell of resistance in Moss Landing’s wake. A Change.org petition to stop new battery facilities in Santa Cruz and Monterey counties — which claims the recent battery proposal places the region “under threat” — has garnered over 4,500 signatures since mid-January. People from across Santa Cruz County are increasingly showing up to board of supervisors meetings — the body responsible for approving such a project — to call for a moratorium. The visual of the 100-foot-tall flames shooting from the Moss Landing facility has been burned into the public consciousness, and those thick plumes of toxic smoke have left a bad taste in many mouths — in some cases, literally. 

Like the concerned residents, most, if not all, experts in the field of battery storage view the Moss Landing fire as a failure – but as many believe it is an anomaly, highly unlikely to repeat in the U.S. thanks to safety regulations and design standards adopted since Vistra completed the first, and now-charred, phase of its Moss Landing battery system. (The Vistra campus hosts three separate battery facilities that, when combined, make up one of the world’s largest systems.)

New Leaf Energy has worked to combat growing battery madness by promoting the ways its project is more state-of-the-art and, thus, safer. Yet, the differences do not, in all cases, mean safer, experts say. 

In talking about the project, Max Christian, New Leaf’s energy storage developer, is energetic in distinguishing Seahawk from Moss Landing, but careful not to presume the project will be approved. He said the Vistra incident was a failure that should “never happen again,” and said he believes that for next-generation battery storage facilities, it won’t.

“It’s impossible to have a fire event at the scale that we saw at Moss Landing at a next-generation facility,” Christian said. He acknowledged that was “a bold statement,” but said “we believe our design mitigates all the known risks” that made January’s fire possible.

Christian said the “first, biggest difference” is the battery chemistry. In Moss Landing, Vistra used what are known as NMC batteries, made of nickel, manganese and cobalt. Today, at utility scale, NMC batteries are seen as more volatile and prone to thermal runaway, a chain reaction that causes a battery to overheat and catch fire or explode. Seahawk proposes to use the industry-preferred LFP batteries. Made of lithium, iron and phosphate, these batteries are lighter, cheaper and, according to studies, much less prone to thermal runaway.

However, industry experts say any claim that LFP batteries are inherently safer than NMCs is misleading.

A 2024 meta-analysis by a team of researchers out of the University of Sheffield in England found that although LFP batteries are much less likely to experience thermal runaway, once they do catch on fire, they are “significantly more toxic” than NMCs. Although LFP fires and thermal runaway are rarer, the study concluded that the batteries pose a greater hazard of combusting and emitting toxic gas when experiencing thermal runaway than NMCs.

Professor Dustin Mulvaney, who received his doctorate in environmental studies at UC Santa Cruz and now teaches at San Jose State University, said the difference between NMC and LFP batteries is a matter of tradeoffs, not lowered risk. Mulvaney, who has been studying the impact of battery storage facilities for years, with a special interest in Vistra’s Moss Landing plant, said using LFPs trades “the risk of a fire and thermal runaway for a more complicated emergency response,” as burning LFP batteries are inherently more dangerous. 

“By using LFPs, you’re lowering the risk of fire, but when a fire does happen, you have firefighters that are put in harm’s way because they are putting out a fire that has a greater risk of exploding” because of the chemical composition, Mulvaney said. “I think developers are right to say that LFPs reduce the chance of having thermal runaway, but I wouldn’t say it’s less risk. It shifts the risk from the cause of the fire to the fire response.” 

Mulvaney argued the more important safety enhancements for the Seahawk project are the fact that its batteries will need a formal safety certification — which he said didn’t exist when the Moss Landing facility was completed in 2021 — and its layout. 

The batteries that burned in Moss Landing were held in a densely packed row of steel containers and housed indoors inside a retrofitted concrete structure. Details are still emerging about how the fire started, but the early reports claimed that the fire began in one battery container and after several hours spread to other, nearby containers, fueling the blaze.

Most every expert who has since looked at that early Moss Landing layout has called it a relic that couldn’t be repeated in today’s regulatory environment. The industry standard still houses the batteries inside sealed, steel shipping containers, but those containers now sit outdoors, each separated by several feet. Later phases of Vistra’s Moss Landing facility were developed using this outdoor format, and New Leaf’s project will abide by these same updated standards.  

During a recent expert panel on battery storage systems, Mark Jacobson, a professor of civil and environmental engineering at Stanford University, said the modern layout keeps fires rare. 

“The reason most battery storage facilities don’t have fires is because they’re outdoors, in individual containers and are well-ventilated,” Jacobs said. “Better ventilation avoids future fires.” 

If a fire does occur, Christian and Mulvaney said the outdoor separation also makes it easier for emergency responders to contain the spread. If one container overheats or combusts, firefighters douse the sealed battery containers nearby with water to keep them cool while the fire burns out. 

Mulvaney said the industry has been on “a steep battery learning curve” over the past few years. Thanks to increasingly tight safety regulations, he believes the Moss Landing fire will end up being “the biggest battery fire the world will ever see.” However, he said new projects deserve healthy skepticism. 

“Anyone who is going to have a battery storage facility near them is right to raise questions about battery fires at this point because we’ve seen enough of them,” Mulvaney said. “It’s probably unlikely that we’re going to be able to stop all battery fires, but we can sure keep them small.” 

Christian, like the rest of the industry, is awaiting the results of Vistra’s and the state’s investigations into the Moss Landing fire, as he said they might hold some new information that could help improve the safety designs of future facilities like Seahawk.

“If there’s anything new that we can apply and incorporate into our project, then yeah, let’s do it,” Christian said.

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