Study on gas diffusion laws and fire protection ventilation performance during battery thermal runaway within energy storage cabinets

To address catastrophic accidents like fires and explosions caused by flammable gas release during battery thermal runaway within energy storage cabinets, this paper establishes a numerical model simulating gas leakage, diffusion, and ventilation processes based on thermal runaway gas diffusion theory. The paper investigates the diffusion laws of thermal runaway gases under confined conditions following pressure relief valve activation, as well as the gas expulsion characteristics under different air distribution and exhaust volumes. The study reveals that thermal runaway gases reach the cabinet ceiling within 30 s after valve activation, exhibiting a distinct “vertical-horizontal-sedimentation” diffusion pattern and forming a concentration gradient layer. Compared to dilution ventilation, local ventilation demonstrates a marked advantage in controlling thermal runaway gases. A ventilation strategy employing front-top exhaust vents and rear-bottom air inlets generates an effective longitudinal barrier that significantly suppresses transverse gas dispersion. Furthermore, the expulsion performance of thermal runaway gases improves substantially with increasing air exchange rates. Based on these findings, a design methodology integrating air distribution and exhaust volumes for modular energy storage cabinet fire protection and ventilation systems is proposed, laying both theoretical and engineering foundations for the fire protection ventilation design and safe operation of battery energy storage cabinets.