# A Comprehensive Literature Review on Hydrogen Tanks: Storage, Safety, and Structural Integrity
## 5 Fundamental Issues
### Safety and Risks
#### 5.3.1 Explosions  
A significant risk related to hydrogen tank safety is the possibility of explosions [8; 16]. [PERSON] et al. [189] focused on developing and validating a CFD model to simulate the dynamics of blast waves and fireballs following the rupture of high-pressure hydrogen tanks in a fire. The overall goal is to enhance the understanding of the consequences of hydrogen tank rupture and enhance safety engineering and infrastructure development related to hydrogen storage. Improving a previous work on the same wave [135], this study combines experimental data with numerical analysis to gain insights into these phenomena. It finds that the release of chemical energy during combustion significantly affects the blast wave's pressure and impulse. Key findings include the quantitative impact of hydrogen combustion on blast wave strength and the effect of different tank rupture modalities. CFD was also used by [PERSON] et al. [190] in a similar analysis.  
On the same topic, explosions and fireballs in a fire environment have been analyzed to develop safety strategies for hydrogen tanks [138]. [PERSON] et al. [191] examined the catastrophic rupture of high-pressure hydrogen storage tanks in fire environments, highlighting the combined physical and chemical explosion hazards. They revealed that fire conditions significantly lower the failure pressure of a 6.8 L-30 MPa tank, causing brief deflagration and giant fireballs. Fragments disperse with high kinetic energy, posing risks over large areas. The study proposes a standardized procedure to evaluate blast wave overpressure and defines risk zones based on experimental data to improve safety for high-pressure hydrogen storage systems. Similar results have been obtained by [PERSON] et al. [173] and [PERSON] et al. [192]. They provide comprehensive insights into the thermal performance and hazard assessment of high-pressure hydrogen storage tanks under fire exposure. [PERSON] et al. [173] conducted three bonfire tests on 210 L, 35 MPa composite type III hydrogen tanks to investigate their response in fire scenarios, revealing that failure pressures ranged from 41.1 to 41.8 MPa, with significant reductions in load-bearing capacity under thermal conditions. Their results showed that the Fire Resistance Rating (FRR) varied, with tanks without Thermal Pressure Relief Devices (TPRD) exhibiting longer FRR but decreasing when exposed to engulfing fires before hydrogen blowdown [57; 173]. Complementing these findings, [PERSON] et al. [192] presented engineering correlations for assessing hazard distances defined by fireball sizes following LH\({}_{2}\) spills or high-pressure hydrogen tank ruptures. Their theoretical and experimental analyses provided conservative correlations for fireball sizes, considering factors such as hydrogen mass and fireball geometry. Together, these studies underscore the importance of understanding tank failure mechanisms and fireball dynamics to enhance safety measures and design considerations for hydrogen storage systems.  
Additionally, [PERSON] et al. [15] investigated the explosion of a 35-MPa, 72.4 L hydrogen tank at different heights and orientations from the ground, finding that tank height and position significantly affect blast overpressure strength and propagation. Their numerical predictions indicated hydrogen explosions closer to the ground auto-ignite due to the Mach stem phenomenon, which resulted in more hazardous blast effects in the radial direction. The study further concluded that human fatalities could occur up to 2 m from the explosion center, with severe injuries up to 7 m and minor injuries beyond that. Tilting the hydrogen tank increased the potential blast hazards and injuries compared to horizontally placed tanks, highlighting the importance of tank positioning in mitigating explosion risks.