# A Comprehensive Literature Review on Hydrogen Tanks: Storage, Safety, and Structural Integrity
## 5 Fundamental Issues
### Design Technology of Tanks
#### 5.2.3 Thermal Performance  
Strictly connected to the design and the choice of the material of the tanks (Sections 5.2.1 and 5.2.2), the thermal performance and management are one of the most studied factors about the storage and safety of the high-pressure hydrogen tanks [140; 173; 174]. One of the most impressive studies was conducted by [PERSON] et al. [178]. The thermal performance of LH\({}_{2}\) storage tanks, particularly in minimizing heat ingress to reduce boil-off gas losses, reveals significant differences between tank designs. Spherical tanks, with a smaller surface area than cylindrical tanks of equal storage volume, experience the slowest pressure increase during self-pressurization due to efficient heat transfer. Horizontal cylindrical tanks exhibit a slower pressure increase than vertical cylindrical tanks because they facilitate more efficient heat transfer between vapor and liquid phases, reducing the temperature difference. As a result, spherical tanks offer the longest holding time, while vertical cylindrical tanks have the shortest, assuming the maximum allowable working pressure remains constant. Higher liquid levels in the tanks contribute to decreased evaporation rates due to the more considerable thermal mass inertia, with evaporation rates following an ascending order from horizontal cylindrical to spherical to vertical cylindrical tanks. Under atmospheric pressure, the temperatures of the vapor and liquid phases maintain stability in a quasi-steady state, and the continuous decrease in liquid level due to evaporation has minimal impact on the evaporation rate. Both horizontal and vertical cylindrical tanks demonstrate similar thermal performance regarding liquid phase temperature, liquid level, and evaporation rate. However, spherical tanks stand out with the lowest evaporation rate due to reduced heat transfer from the environment, with the expansion of the vapor phase volume having a negligible impact on the evaporation rate. The work by [PERSON] et al. [165] on evaporation analysis of LH\({}_{2}\) tank under various heat flow conditions demonstrated that internal pressure increases with higher heat flux rates, and the insulation analysis reveals that decreasing thermal conductivity with reduced vacuum pressure effectively suppresses evaporation and lowers internal pressure. Insulation is still a critical problem while designing hydrogen tanks [150]. [PERSON] et al. [139] investigated the impact of substituting chromium (Cr) and vanadium (V) into ZrFe\({}_{2}\)-based alloys on their equilibrium pressure and thermodynamics for hydrogen storage, demonstrating that ZrFe\({}_{2}\)-based alloys are promising candidates to composite with high pressure compressed hydrogen tanks and thus reduce the working pressure and volume of high-pressure tanks. [PERSON] et al. [179] analyzed the safe usage of GH\({}_{2}\) in vehicles using a CFD analysis, demonstrating that tank temperatures must not exceed 85 \({}^{\circ}\)C [180] and revealing the potential for vertical thermal stratification during the filling of horizontal tanks. [PERSON] et al. [169] provided detailed insights into the temperature-dependent mechanical properties of HDPE used in high-pressure hydrogen storage vessels for automobiles. Experimental investigations revealed that Young modulus and tensile strengths of HDPE significantly increased with decreasing temperature, with Young modulus ranging from 83 N/mm\({}^{2}\) at 373 K to 2381 N/mm\({}^{2}\) at 223 K, and tensile strengths increasing from 4.9 N/mm\({}^{2}\) at 373 K to 40.1 N/mm\({}^{2}\) at 223 K. The compressive to tensile stress ratio exhibited nonlinear behavior depending on temperature and strain range. Finite element simulations using an elastic-plastic model with isotropic hardening and a hyperelastic model demonstrated good agreement with experimental stress-strain data, with minimal relative errors under tensile and compressive loading conditions. Another critical issue pertaining to thermal management is tank filling. In their research, [PERSON] et al.