Advancing safety of hydrogen polymeric tanks: A review of permeation mitigation, leak detection, and smart monitoring

The current and future working horse for mobile hydrogen storage are Type IV and V tanks, respectively, which are manufactured fully from polymeric materials. Even in the absence of a critical event damaging the tank, hydrogen diffuses through the polymeric matrix that results in serious safety concerns. This review focuses on detecting and reducing the root cause of hydrogen leaks (permeation and damage) in these tanks. The permeation of hydrogen in the absence and presence of damage in Type IV and V tanks was reviewed, highlighting the main technical challenges and research gap. The possible techniques for mitigating hydrogen permeation, including matrix additives, coatings, and thin-ply composites, were discussed. Additionally, different sensing techniques for hydrogen leaks were discussed highlighting their advantages and limitations of use in terms of enhancing the safety of tanks. Finally, the deployment of machine learning in different aspects of tank design and structural health monitoring was examined. The paper concludes with a perspective toward future smart sustainable tanks composed of thin-ply thermoplastic composites coupled with flexible wireless integrated hydrogen sensors.