Performance-based assessment of an explosion prevention system for lithium-ion based energy storage system

Abstract

This work developed and analyzed a design methodology for Powin Stack™ 360 enclosures to satisfy the requirements for explosion prevention per NFPA 855. Powin Stack™ 360 enclosures are lithium-ion-based stationary energy storage systems (ESS). The design methodology consists of identifying the hazard, developing failure scenarios, and providing mitigation measures to detect the battery gas and maintain its global concentration lower than 25% of the lower flammability limit (LFL) to meet the prescriptive performance criterion of NFPA 69 – Standard on Explosion Prevention Systems. The UL 9540A test data is used to define the battery gas composition, release rate, and release duration to describe the failure scenario involving thermal runaway propagation. The ESS enclosure consists of individual stacks (compartments) with targeted airflow to ensure the cooling of batteries during normal operational conditions. This arrangement makes it difficult to use a standard exhaust ventilation methodology to design an explosion prevention system. An innovative approach is used to purge the battery gas from individual Powin Stacks™ and from the main enclosure during a thermal runaway event. The designed method is analyzed using a computational fluid dynamics (CFD) model to ensure it meets the intent of NFPA 69. The explosion prevention system functionality presented in this work is limited to removing flammable battery gas generated due to the non-flaring decomposition of batteries and does not consider its interactions with other fire protection features.