An Untold Success Story

As battery energy storage proliferates, fires and safety incidents remain rare. Research and collaboration explain why.

By Chris Warren

It’s not hyperbole to say that April 19, 2019, marked a sharp turn in how North American utilities, manufacturers, safety code and standards developers, and other stakeholders view battery energy storage system (BESS) safety. It was on that spring day in Surprise, Arizona, that an explosion and fire at the McMicksen BESS injured four firefighters.

A later report found that the incident was caused by an internal failure in a single lithium-ion cell that began a thermal runaway. The resulting explosion and fire were not the first energy storage accidents. In South Korea, there were 28 battery fires between 2017 and 2019, enough to halt the country’s energy storage market. However, in the U.S., it took the high-profile incident in Arizona to prioritize BESS safety in a way it hadn’t been before.

“I was at a conference a week before the Surprise, Arizona incident where everybody was saying that lithium battery technology safety is solved and that it was a problem in South Korea only,” said Lakshmi Srinivasan, principal team lead for energy storage at EPRI. “Six months later, everyone at the next version of that conference was talking about safety all the time. There has been a sea change, and now, five years later, it is a driving factor in BESS design along with the development of products and technologies that specifically focus on lithium-ion battery safety.”

The industry reaction to safety incidents in Arizona and South Korea is not a story that is often told. If anything, news stories raising concerns about the safety of BESS and the adequacy of emergency response have proliferated over the past year. For example, an e-scooter explosion in New York City led to a large fire and increased scrutiny of lithium-ion battery safety. Three subsequent fires at grid-scale energy storage facilities in New York prompted Governor Kathy Hochul to convene a working group to evaluate the health and environmental impacts of battery fires and to develop fire codes and other recommendations to help prevent future incidents.

As Storage Deployments Soar, Fire, and Safety Incidents Remain Constant

Given the intense media coverage of energy storage incidents, it would be reasonable for communities where projects are proposed to question the safety of installing lithium-ion batteries. However, the larger context of BESS safety has been missing from a lot of media coverage and analysis of these individual incidents. Or, to put it more plainly, are lithium-ion battery fires the norm or rare exceptions?

In late 2023, EPRI released a Technology Innovation spotlight, Lithium-Ion Battery Fires in the News, which used public data to provide insight into the prevalence of energy storage failure incidents. EPRI was well-positioned to objectively assess the frequency of battery fires. Since 2021, EPRI has maintained the publicly accessible BESS Failure Incident Database, which tracks global grid-scale battery failures dating back to 2011. “We’re only able to record incidents that are mentioned in the news, or that people inform us about, so we can’t guarantee that the database includes all incidents,” Srinivasan said. “But we have the most comprehensive data set available.”

That data set paints a very different story about lithium-ion battery safety than one might infer from the news coverage. Indeed, Srinivasan and Stephanie Shaw, an EPRI technical executive, compared the average frequency of energy storage incidents and the technology’s rapidly increasing deployment. “We saw that deployment exponentially increased from one gigawatt deployed globally in 2018 to 65 gigawatts in 2023,” Shaw said. “Despite that 65-fold increase in deployment, you’re still seeing about ten incidents globally on average. That number is not going up as battery deployments are increasing at an incredibly fast pace over the same time period.”

Obviously, grid-scale batteries aren’t the only energy storage technology. For the Technology Innovation spotlight, EPRI also examined battery fires and incidents involving electric vehicles (EVs) and micro-mobility sectors, including electric scooters and bikes.

A Collaborative Response

Though it is less likely to grab headlines and clicks, the story of the collective reaction to high-profile lithium-ion battery fires and explosions is both a success and still unfolding. “Any battery failure is one too many,” Shaw said. “You can reduce the impact and probability of a failure, and the trend in the right direction is clear from the data. The industry has incorporated a lot of lessons learned and is improving safety regulations and the range and effectiveness of mitigation technologies. Those combined actions have substantially reduced risks.”

For example, insurance companies today work much closer with energy storage developers to base premiums on comprehensive assessments of fire and explosion risks and incorporation of clearance distances into project designs to ensure safety if an accident occurs. Since the 2019 fire, Underwriter Laboratories (UL) and the International Electrotechnical Commission (IEC) have updated their safety standards, and the National Fire Protection Agency (NFPA) introduced comprehensive requirements targeting fire safety and emergency planning for energy storage design, construction, commissioning, operations, and decommissioning in 2023.

While codes and standards are important, they are inevitably playing catchup with rapid energy storage technology development. Nevertheless, significant investment is going into identifying and preventing possible fires before they start. “There’s an entire section of the industry that’s focused on predictive analytics around safety to prevent these incidents. There are companies developing technology and products focused on identifying failures early, preventing them, and developing new sensing technology,” Srinivasan said.

Helpful to the energy storage industry’s efforts to prevent and reduce incidents and bolster the safety of first responders are EPRI’s many years of research into safety-related topics. The scope of EPRI’s battery safety research is sprawling and includes input and support from about 25 utilities, project developers, and insurance companies in the U.S. and around the globe. The research also benefits from the knowledge and experience of representatives from fire departments, fire safety experts, insurance agencies, academic institutions, and national laboratories.

EPRI has also worked with a broad collection of stakeholders to develop a roadmap for future research to close knowledge gaps. For example, one near-term focus area for EPRI and its collaborators is improving the quality of publicly available data about battery fires. “One of the gaps we identified is the need for more public data sets on exactly the sort of failure characteristics and some of the gas and thermal details about how a fire happens and how it may differ depending on different chemistries and different product configurations,” Shaw said. Improved data and information will also support EPRI’s project life cycle safety toolkit, which already provides guidance to bolster safety at each phase of an energy storage project.

What if Everything Goes Right? The Community Benefits of Energy Storage

One objective energy storage safety research does not seek is to dismiss or diminish the questions and worries people raise when battery projects are being developed in their communities. “There might be a lot of misinformation, but there are also legitimate concerns around the public health, safety, and environmental impact in the event of lithium battery fires,” Srinivasan said.

The goal for battery storage developers, utilities, and other stakeholders should always be complete transparency about the low incidence of safety incidents and acknowledge what is not well understood yet—such as the contamination levels of water used to put out battery fires. An emphasis on science-based facts and transparent communication can also build trust and drive broader conversations about the community benefits of energy storage projects.

Some benefits of energy storage can seem removed from the tangible, day-to-day concerns among community residents. While it’s true that energy storage enables decarbonization and provides vital grid services, for instance, communities often have more pressing economic, equity, and workforce development priorities. Energy storage developers, utilities, and others need to communicate better, listen, and engage with communities about the benefits projects can deliver and the outcomes residents seek. “What if everything goes right? What do communities get out of this?” Shaw said.

The answer depends on what communities care about, but there are many possible advantages energy storage can deliver. For example, battery storage—especially as part of a microgrid—can improve the reliability, resilience, and accessibility of emergency services in the face of extreme weather. Battery storage projects can also reduce energy bills and result in workforce education and training that can improve the financial situation of individuals and families in a community. Guidance and recommendations about how energy storage stakeholders can work collaboratively with communities to maximize the project’s benefits is the topic of an upcoming EPRI white paper, Community Benefit Planning for Energy Storage Projects.

The story of enhanced energy storage safety in a rapidly growing industry needs to be told more frequently, emphasizing the positive underlying data and commitment to continuous improvement. But that is not enough by itself. An even better story will emerge as communities are engaged early and continuously to connect energy storage projects to the priorities they care most about.

Additional information about EPRI’s ongoing collaborative research is available through the BESS Fire Prevention and Mitigation Phase III Supplemental Project.

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