A CFD based methodology to design an explosion prevention system for Li-ion based battery energy storage system

This work developed a performance-based methodology to design a mechanical exhaust ventilation system for explosion prevention in Li-Ion-based stationary battery energy storage systems (BESS). 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. Representative 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. In addition, an exemplar BESS enclosure geometry is defined to model the failure scenarios using a computational fluid dynamics (CFD) solver. A grid convergence study is performed to estimate the grid resolution required to perform the CFD analysis. In addition, sensitivity studies for different input parameters are performed to understand the impact of inputs on the detection times and ventilation performance. The approach used in this work provides a systematic procedure for the fire protection engineering community to understand the explosion prevention requirement for a BESS installation. 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.