Preliminary assessment of a fault that caused Vistra’s flagship 300MW/1.2GWh energy storage system (ESS) to overheat and go offline has begun in the US state of California.
Phase I of the Texas, US, firm’s Moss Landing Energy Storage facility was forced out of service following an “overheating incident” that affected a number of battery modules around 8pm on 4 September.
The system is made up of more than 4,500 stacked battery racks or cabinets, each containing 22 individual battery modules manufactured by LG Energy Solutions.
Vistra said that it was taking a conservative approach and keeping the entire facility offline as it investigates the root cause of the incident in partnership with its engineering contractor Fluence, and battery manufacturer LG Energy Solution.
California news outlet Kion 5/46 quoted North County Fire District fire chief Joel Mendoza as saying the battery racks had been "scorched" and wires "melted."
He was reported as saying: "We didn’t see any fire when we came in. What we saw was a lot of smoke. The battery modules are actually encased in plastic. So in the event of overheating, you’re gonna see a lot of smoke."
Safety systems detected the faulty modules were operating at a temperature above operational standards and triggered sprinkler systems targeted at the affected modules.
The operational status of the assets of Phase II (100MW), which is located in a separate stand-alone building, remains operational. Phase II was completed last month and brought the facility's total capacity to 400MW/1.6GWh— the largest of its kind in the world.
Battery fire investigation
Teams from Vistra, LG Energy Solution, Fluence, and other external experts are in the early stages of the investigation into the root cause of the issue.
The teams expect that it will take “some time” to fully assess the extent of the damage before developing a plan to safely repair and return the battery system to operation.
The North County Fire Protection District of Monterey County is assisting with the investigation.
A statement by Vistra on 5 September read: “The Moss Landing Energy Storage Facility experienced an overheating issue with a limited number of battery modules in its Phase I 300-megawatt/1200-megawatt hour system.
“There are multiple layers of safety integrated into the battery facility and the risk mitigation and safety systems worked as designed, detecting these modules were operating at a temperature above operational standards and triggering targeted sprinkler systems aimed at the affected modules.
“As a result, the overheating was controlled and contained without the need for outside assistance. However, consistent with Vistra’s incident response planning and out of an abundance of caution, the Moss Landing team did ask the local fire department, North County Fire Protection District of Monterey County, to respond to the site.
“Importantly, there were no injuries to the facilities’ workers as a result of the incident and the situation is contained to the facility with no harm to the community.”
Vistra is uncertain on the timing of the return of the facility, pending an investigation and any needed repairs.
The company will update the status of Phase I Moss Landing as it learns more.
LC Chem battery woes
It has been an interesting year for LG Energy Solutions, the subsidiary of the Korean battery giant LG Chem.
Earlier this month, a billion dollar recall of GM’s electric vehicles was made after a torn anode tab and a folded separator were found on cells. LG packs the cells into the modules, then into a battery pack battery at LG Energy Solution Michigan facility in Holland, Michigan, US.
In August, LG Energy Solution extended its scheme to replace lithium-ion batteries used in its home energy storage systems (ESS) to include all geographical markets.
ESSs manufactured between April 2017 and September 2018 are being recalled due to overheating concerns.
