The Moss Landing Energy Storage Facility Phase II in the United States set off fire alarms that activated a fault water suppression system, triggering a cascading set of events that resulted in roughly 10 battery packs melting down.

From pv magazine USA

The Vistra Energy Moss Landing Energy Storage Facility Phase II set off fire alarms just after 8 p.m. (PST) on Feb. 13. Upon arrival, the local fire department found roughly 10 battery racks that were completely melted. The fire department representatives said that the fire was extinguished.

“We could confirm that it does have a fire suppression system, that the fire suppression system activated, and actually extinguished or cooled the batteries to the point where there wasn’t any flame or fire,” North County Fire District Chief, Joel Mendoza told local media outlets.

Vistra Energy later released an official statement on its website. The company says the onsite fire suppression systems performed as required, at least in the sense that the fire incident was isolated.

The California ISO energy website does show a drop in battery output at 7 p.m., local time. There is no indication this is related to the Moss Landing facility.

Vistra has suggested that the event might be a similar event to a September incident that took down the first phase of the facility. According to a statement from Vistra, that incident involved a cascading series of events which may have started with the failure of a ball bearing in a fan.

The suspected bearing failure is presumed to have set off the very early smoke detection apparatus (VESDA), which in turn armed the heat suppression system. Vistra stated that due to “failures of a small number of couplings on flexible hoses and pipes,” water sprayed directly onto additional battery racks, causing short circuiting and arcing, which damaged the batteries and made more smoke. The additional smoke set off more alarms and caused even more water to spray from the failed couplings.

While the cascading events following the smoke detection can be seen in the data, investigators have not explicitly determined what set off the smoke alarm in the first place.

Vistra says that they had been bringing the first facility back online incrementally, but have now decided to pause those activities. Pv magazine was not able to confirm whether any of the larger facility’s capacity has come back online.