Battery Energy Storage System (BESS)
Battery installation providing energy storage and discharge to stabilize supply and support critical loads.
A battery energy storage system stores electrical energy to discharge it when needed, ensuring supply continuity, peak shaving and the integration of intermittent renewable sources. In data centers, it complements or gradually replaces traditional uninterruptible power supplies and generators to support critical loads during a grid outage. Massive recourse to battery storage, often lithium-based, introduces a specific fire peril, however: the thermal runaway of a cell can propagate and trigger a loss that is hard to extinguish, releasing toxic gases. For insurance, the BESS has become an underwriting subject in its own right, at the crossroads of fire risk, environmental risk and business interruption risk. The novelty of large installations and the rapid evolution of battery chemistries maintain high uncertainty over the real frequency and severity of losses.
The fire at Vistra's battery storage plant at Moss Landing, California, which broke out on 16 January 2025, showed that thermal runaway in lithium modules can cause a long-duration fire, and set fire underwriting a novel challenge.
BESS, battery storage, battery energy storage system
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