Water based suppression system leak causes battery shorting at Moss Landing Phase II

On 13 February 2022, an early detection safety system activated at the 100 MW Phase II building of the Moss Landing Energy Storage Facility in Moss Landing, California, operated by Vistra Energy. An investigation found that the water-based suppression system released water that contacted batteries, and there was early evidence that water hoses leaked, causing some batteries to short and create smoke inside the building. Firefighters who attended found around ten melted battery racks. The building's systems contained the event without requiring outside firefighting assistance, although off-site emergency responders were contacted as a precaution. No injuries to personnel were reported. The Phase II system was taken offline following the incident, and restart of the adjacent Phase I facility, which was unaffected, was paused while the operator assessed the Phase II event and incorporated any lessons learned.

Early evidence pointed to leaking water hoses in the water-based suppression system, which allowed water to contact batteries and cause shorting, similar to a prior incident at the adjacent Phase I facility in September 2021.

1. Water-based suppression systems used in battery storage buildings should be inspected for hose and seal integrity to prevent leaks that could bring water into contact with energised battery equipment.
2. Recurring incident types at co-located or adjacent facilities should trigger a broader review of shared design, suppression system specification and maintenance practices across all phases of a site.
3. Pausing restart activities at unaffected adjacent systems to incorporate lessons from a related incident is a prudent precaution before returning equipment to service.

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