Major California Battery Outage Highlights Energy Storage Risks
by Edward Klump
Sep. 13, 2021 (abridged) – A massive U.S. battery storage project is offline in California.  That stokes reliability and safety questions about a technology that will be crucial to meeting future clean electricity goals.
Overheating battery modules on Labor Day weekend affected a 300-MegaWatt (MW) facility at Vistra Corp.’s Moss Landing energy storage site.  But the implications go beyond any one state, company or project.
That’s because energy storage offers one path to help offset the intermittency of fast-growing renewable energy capacity.  A reliability problem with batteries is among the factors that could hamper the Biden administration’s efforts to decarbonize the U.S.  power sector by 2035, not to mention countless mid-century state and corporate clean energy goals.
Experts caution that adjustments — from battery chemistry to management systems — may be needed to ensure that large battery sites can stay online, especially as their role on the grid grows.  There’s hope the industry will rise to the challenge, though changes come with costs.
“I do not think we should understate the importance of safety,” said Kelsey Hatzell, an assistant professor at the Andlinger Center for Energy and the Environment at Princeton University, who studies batteries.  “But I am optimistic that we can engineer for safety.”
Battery issues have occurred over the years, in everything from personal devices to automobiles.  For the power sector, issues may be relatively isolated.  But a fire in Arizona in 2019 illustrated the need for vigilance around energy storage, and electric utility Arizona Public Service paused new battery storage projects after that event.
The recent overheating at Moss Landing, which uses a lithium-ion battery system, saw targeted sprinklers deployed and firefighters called.  Texas-based Vistra, often known for its fossil fuel and nuclear generating units, as well as an electric retail business, said the situation was contained.  A separate 100-MW battery storage expansion at Moss Landing remained operational last week, and Vistra said Moss Landing also has a roughly 1,000-MW facility fueled by natural gas that’s available.
Vistra said it is investigating the overheating, along with other parties.  LG Energy Solution has been involved at Moss Landing as a battery manufacturer.
“A root cause analysis is underway and significant work is being done to determine exactly what happened,” Vistra spokesperson Meranda Cohn said in a statement to E&E News.  “But it will take time.”
Cohn pointed to the size of the 300-MW facility and battery system, saying there are “more than 4,500 racks or cabinets that each contain 22 battery modules — that’s nearly 100,000 modules … and we will inspect every one of them.”
She also said that “at this point in our investigation, there is not an indication of fire.” Cohn said people and communities were kept safe during the event.  Vistra indicated the overheating affected a “limited number” of modules the evening of Sep. 4.
“We are confident it is a matter of when, not if, the facility returns to service,” Cohn said.  “However, speed is not our goal here — safety is.”
Without knowing specifics of the Moss Landing situation, Hatzell said overheating with batteries can be the result of manufacturing defects.  A malfunction that results in use of a sprinkler system suggests a battery was not operating properly, she said.
“That is a last resort that you have sprinklers, you know, rain on your batteries,” Hatzell said.
The series of events marked a turnaround from last month.  That’s when Vistra trumpeted the storage expansion at Moss Landing, with Vistra CEO Curt Morgan saying the site helps fill a “reliability gap” by storing excess daytime power and sending it to the grid when needed.  Vistra said the facility’s total capacity of 400 MW/1,600 MW-hours made it “the largest of its kind in the world.”  The company has said there’s the potential to further expand Moss Landing’s storage capacity, as well. 
The Goldilocks Temperature
Matthew Keyser, a senior engineer at the National Renewable Energy Laboratory, said grid storage is going through an evolution, as more and more energy is being put into a smaller space with batteries.
He likened it to the Goldilocks fairy tale with different temperatures of porridge, as battery lives can fluctuate based on conditions including heat and voltage.  “Batteries don’t like to be too hot,” he said.  “They don’t like to be too cold.  They like to be just right.”
According to Keyser, there are maybe 1 in 10 million defects among lithium-ion batteries — and that ratio should improve over time.  But he said defects can have an impact with millions of batteries produced daily.
Hatzell said battery chemistry for energy storage is being re-imagined right now — or at least reexamined.  “Looking at materials that are more thermally stable is definitely a direction that needs to be … propelled forward for these particular applications, where you have 1,000s and 1,000s of batteries,” she said.  “We just know that they heat up.”
California has seen some tight grid conditions in recent years amid heat and wildfires, and it has sought to push ahead with more energy storage.  So the overheating at Moss Landing didn’t go unnoticed.
Anne Gonzales, a spokesperson for the California Independent System Operator, said via email that “the outage caused no overall impacts to the stability of the bulk electric system.”...
Jason Burwen, interim CEO of the U.S.  Energy Storage Association, said in a statement that professionally designed and installed battery systems incorporate “rigorous safety standards with modern monitoring systems.”...
“The safety systems in place for the Moss Landing project worked as designed to notify operators of overheating,” Burwen said.  “Grid operators, including California’s, expect to rely on increasing levels of energy storage to meet decarbonization and reliability goals.  And we don’t see that changing because of what happened with the Moss Landing project.” 
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www.eenews.net/articles/major-calif-battery-outage-highlights-energy-storage-risks/