Analysis of the behaviour of liquid hydrogen (LH2) tanks under fire exposure

In the ongoing energy transition, liquid hydrogen (LH₂) stored and transported in cryogenic tanks insulated with multilayer insulation (MLI) is emerging as a promising energy carrier with low environmental impact. To preserve the structural integrity of these systems under both normal and abnormal conditions represents a crucial challenge for their widespread adoption. Despite insulation, fire tests have shown LH₂ tanks may fail catastrophically under fire exposure. This was largely attributed to MLI degradation, leaving the tank unprotected. However, the few fire tests on LH₂ tanks and the lack of investigations into the MLI behaviour have constrained understanding of tank response to fire. This work addresses these gaps by combining experimental and modelling efforts. The experimental activities characterized the high-temperature degradation and performances of MLI materials using both conventional methods and novel techniques. An innovative experimental apparatus was developed to impose fire-like thermal loads while measuring heat flux through the insulation. Test results revealed the pronounced degradation of MLI systems under typical fires. Complementary thermal analyses were performed to characterize degradation mechanisms at fire-like temperatures. Based on these insights, innovative MLI configurations with enhanced fire resistance were designed and tested. The experimental dataset served as the benchmark to develop innovative heat-transfer and thermal-degradation models for MLI under fire exposure, obtaining accurate simulations of the experimental results. Thus, an original approach to the fire safety assessment of MLI-equipped LH2 tanks in fire scenarios was developed. A novel model integrating the high-temperature degradation of MLIs and the thermodynamic modelling of the tank load was coupled to specific key performance indicators. This was applied to a representative vehicle-scale LH₂ tanks under varying MLI configurations, operational conditions, and fire scenarios. The findings deliver crucial insights to support safer LH₂ tank designs, emergency response planning, and guide mitigation strategies for preserving tank integrity.