Battery fire at Valley Center Energy Storage System, California

In September 2023, a fire occurred in the late afternoon at the Valley Center Energy Storage System in Valley Center, San Diego County, California, operated by Terra-Gen. Fire and sheriff's departments were dispatched, roads in the area were closed, an evacuation order was issued for an area within about a quarter of a mile of the site, and shelter in place advice was given for an area of about half a mile. Reporting indicated that the fire involved approximately 100 lithium-ion battery packs which, according to later statements from Terra-Gen, had been decommissioned, palletised and were awaiting collection for recycling. Those packs had been taken out of service after a sensor system fault activated the water based protection system. Public safety measures were lifted about four hours after the fire was reported, and Terra-Gen stated that the incident was concluded by the following morning. No injuries were reported.

Sources reported that the cause of the fire was under investigation at the time of publication. Statements from Terra-Gen described an earlier sensor system fault that activated the water based protection system, after which the affected battery packs were decommissioned, palletised and stored on site pending removal for recycling. Terra-Gen also stated that the decommissioned units were segregated from operating equipment and that the site containment arrangements limited the extent of the fire. No mechanism linking the earlier fault or water exposure to the fire had been publicly confirmed at the time of reporting.

Lessons drawn from the publicly reported circumstances:

1. treat "decommissioned but still on site" as a distinct operational state in the safety case, with defined containment, monitoring and emergency response provisions equivalent to those for operating equipment;
2. set and track a maximum dwell time for decommissioned or damaged packs held on site awaiting collection, and escalate when that time is exceeded;
3. where cells or packs have been wetted by activation of a water based protection system, obtain manufacturer or specialist advice on segregation, storage and handling before any decision to return them to service or transport them;
4. review the consequences of unintended or false activation of fire protection systems at design stage, including the plant and equipment that would be taken out of service and where it would then be stored;
5. maintain physical separation between decommissioned material and operating equipment, and confirm that separation distances and barriers are reflected in as built records;
6. inform the local fire service when decommissioned lithium-ion equipment is stored on site, including quantities, chemistry where known and storage location, and update that information as stock changes;
7. record the sequence of protection system activations, decommissioning decisions and storage arrangements so that any later investigation can test whether a common cause links them.

energy-storage.news/terra-gen-to-investigate-cause-of-valley-center-battery-...