Overheated batteries force shutdown of Vistra's 300-MW Moss Landing Phase I

Most of Vistra's flagship 400-MW Moss Landing Energy Storage Facility in California is shut down after battery modules overheated, leading the company to take the facility's Phase I offline as it investigates the cause.

Late Sept. 4, battery modules overheated at the 300-MW Phase I system, which triggered targeted sprinkler system aimed at the affected modules, according to a statement by Vistra Sept. 5.

"With safety as its No. 1 priority, the company is 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," Vistra said in the statement. "Vistra is uncertain on the timing of the return of the facility, pending an investigation and any needed repairs."

No effect on bulk electric system

There were no impacts to the stability of the bulk electric system, California Independent System Operator spokesperson Anne Gonzales said Sept. 7.

"While we don't comment on the performance of specific generators in our system, losing any source of energy at a critical time of the year can be challenging," Gonzales said. "One of any number of resources could make up for the reductions, depending on energy bids coming into the market at the time, including those resources that bid in as imports."

California has the most installed battery storage in the US at 1.390.6 GW, according to the American Clean Power Association's Q2 report. The state has a goal of 100% carbon-free electricity by 2045.

CAISO currently has 1.5 GW of storage on the system and expects to double that by the end of the year.

The overheating at Moss Landing Phase I was contained without the need for outside assistance, but as part of Vistra's incident response plan, the North County Fire Protection District of Monterey County was asked to respond to the site, according to the Sept. 5 statement. There were no injuries.

Phase II operations

The 100-MW Phase II is in a separate building on the site and was not affected by the incident, according to Vistra. Phase II, which started construction in September 2020, remains in operation.

Vistra announced Aug. 19 the completion of Moss Landing Phase II, which brought the facility total capacity to 400 MW, making it the largest of its kind in the world.

"This facility provides a solution California desperately needs, and this expansion was able to come online at the right time -- as the summer heat intensifies and demand for electricity is at its highest," Vistra CEO Curt Morgan said in the Aug. 19 statement. "California produces an excess amount of renewable power during the day while the sun is up but often struggles to meet demand as the sun goes down. Our Moss Landing battery system helps to fill that reliability gap, storing the excess daytime power so it doesn't go to waste and then releasing it to the grid when it's needed most."

The 100-MW Phase II has a 10-year resource adequacy agreement with Pacific Gas and Electric. The 300-MW Phase I project has a similar 20-year resource adequacy agreement with PG&E.