Numerical Study of Hydrogen Dispersion in A Stationary Ni-Cd Battery Room Under Multiple Leak Conditions

The charging of nickel-cadmium (Ni-Cd) batteries in enclosed environments can lead to hydrogen accumulation, posing explosion hazards if ventilation is inadequate. This study applies computational fluid dynamics (CFD) to analyze hydrogen dispersion from stationary vented Ni-Cd batteries under different leak scenarios. The objective is to understand hydrogen accumulation behavior and verify compliance with safety requirements such as the ATEX Directive 2014/34/EU. The analyzed scenario includes a full-scale battery storage room containing typical NiCd installations, simulations were conducted using FLACS, accounting for buoyancy-driven transport, turbulent dispersion, and realistic vent geometries. The study investigates three charging modes (float, boost and exceptional), each corresponding to different hydrogen generation rates. Two ventilation modes are examined to assess their influence on hydrogen accumulation and dispersion. Furthermore, the study discusses whether the simplified ventilation calculation method defined in the regulations provides sufficient safety margins for these operating conditions. The results highlight that hydrogen dispersion is strongly affected by both the release characteristics and the ventilation configuration, demonstrating the need for a detailed assessment of ventilation performance beyond simplified standard calculations. This work demonstrates the capability of CFD to support quantitative safety evaluation of Ni-Cd battery installations. The modeling approach provides a practical framework for verifying ventilation performance and assessing the conservativeness of standard-based design methods. The outcomes contribute to improved design and risk management for stationary battery systems in enclosed environments.

Keywords: Hydrogen dispersion, Ni-Cd battery, ventilation, CFD, FLACS.