Battery storage fire burns for three days at Poggio-di-Nazza site, Corsica

At the Poggio-di-Nazza solar and storage site in Poggio-di-Nazza, Corsica, France, operated by SUN'R and SPES de Corse (also the site owner), and fitted with two lithium-ion battery storage containers using LG Chem battery modules integrated by Nidec ASI, a fire broke out in one container during the evening while the batteries were at around 87 percent state of charge. No staff were on site. A remote monitoring alarm triggered a call to emergency services, who arrived roughly 75 minutes later. The fire began in a single battery module that entered thermal runaway, likely due to an internal cell defect, possibly aggravated by moisture ingress. It spread through the rack to the rest of the container, including a power conversion unit and on-site data servers. The automatic fire suppression system did not stop the thermal runaway. Firefighters focused on preventing spread to an adjacent transformer compartment and to nearby vegetation, using water cooling. The fire burned for more than three days before being fully extinguished. No injuries were reported, though smoke with an acrid odour was noticed by nearby residents over 400 metres away. The full site was shut down for about two months.

The investigation identified an absence of an extinguishing system effective against a thermal runaway event once initiated, loss of internal compartmentalisation within the container, contact between a technician and the site during the response, and challenges in the emergency service intervention. A possible role of moisture from the container's climate control system was also considered as a contributing factor in the initial cell failure, though this could not be confirmed with certainty.

1. Automatic gas-based or inerting fire suppression systems designed for early-stage fires may not halt a lithium-ion thermal runaway once it has begun, and this limitation should be clearly communicated to operators.
2. Structural elements such as container flooring can be a weak point in the fire-resistance rating of a compartmentalised enclosure and should be reviewed in container design.
3. Moisture ingress linked to climate control or cooling systems can contribute to cell or module failure and warrants specific preventive measures and client guidance from manufacturers.
4. Emergency response and site isolation plans should account for the possibility of a battery fire lasting several days rather than hours.
5. Critical monitoring and data servers should not be located inside the same enclosure as the battery racks, to avoid loss of incident data during a fire.

igedd.developpement-durable.gouv.fr/IMG/pdf/rapport_sunr_poggio_vdif_cle5bb821.pdf