Fire Performance of High-Density Cork Agglomerates for Hydrogen Storage Applications

Abstract Hydrogen is recognized as a key energy carrier in the global energy transition. However, ensuring the fire safety of storage tanks remains a challenge. Type I hydrogen tanks lack effective passive-fire-protection strategies, relying predominantly on active devices. Conventional fire-protection materials, including intumescent coatings, aerogels, and ceramics, offer proven performance but are limited by cost, brittleness, and durability constraints. This study presents a systematic evaluation of cork agglomerates as sustainable and scalable alternatives for passive-fire protection of hydrogen tanks. Cork agglomerates with varying densities and thicknesses were characterized in terms of thermal conductivity, diffusivity, and effective volumetric heat capacity. Their fire behavior and heat-conduction performance were assessed under controlled laboratory-scale flame exposure conditions for comparative evaluation. The results demonstrate that increasing density enhances fire resistance, resulting in reduced mass loss and extended failure times. Increasing coating thickness further improves performance, with layers equal to 20 mm maintaining back-surface temperatures below the 136 °C safety threshold. Overall, high-density cork agglomerates exhibited fire-protection performance within the range of conventional alternatives, while offering advantages in terms of renewability and cost-effectiveness. These findings support the use of cork agglomerates as bio-based candidates for passive-fire protection in hydrogen-based renewable energy storage systems.