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No need to worry; Hydrogen's exceptional permeability means the gas will diffuse through the jerry can, into the atmosphere; thus lowering its internal pressure.

We can make vessels which will contain increasingly high pressures; however their permeability is higher, vs. older materials. This is a central problem of hydrogen as a primary fuel... Better to burn it (or convert it into methane) where and when it is produced.

discuss

credit_guy|2 years ago

I keep hearing this, and sometimes people claiming it's not true anymore, so I decided to look into it.

Compressed hydrogen storage tanks are of 4 types [1]. Types 1,2 metal tanks, but they can be used only up to 300 bar. Their permeability rate is negligible. Type 4 is composite (e.g. carbon fiber) with a polymer interior lining. It operates at 700 bar (and various manufacturers state their product can work up to 850 bar). They have some permeability. Type 3 is similar, but with metal interior lining. Negligible permeability, but more expensive. I don't know how much more expensive, with these things all providers tell you to "call for quote".

In any case, the only problem is Type 4. They are the affordable alternative to Type 3, and they are also in much wider use.

There are some regulations and standards that govern them. Specifically EU 406/2010 and ISO 19881:2018 which prescribe a maximum steady state permeation rate of 6.0 Ncm3 of hydrogen per hour and per liter internal volume of the container [2].

To be honest, I'm not sure how to read this rate. Toyota Mirai uses such tanks (2 of them), so it can't be that bad. Each has a volume of about 60 liters, and holds about 5kg of hydrogen [3].

The more important thing is that permeability is a function of the surface area. A tank 1000 times larger has a surface area only 100 times higher, so the permeability per volume goes down by a factor of 10.

Such tanks do exist and are commercially available. I'm aware of the Hexagon Titan XL that can hold 220 kg of hydrogen. The latest quarterly revenues of the manufacturer [4] show 57% year-on-year growth, so it looks like customers are quite happy with their offering.

[1] https://en.wikipedia.org/wiki/Hydrogen_tank

[2] https://www.sciencedirect.com/science/article/pii/S036031992...

[3] https://www.toyota.com/mirai/2023

[4] https://hexagonpurus.com/news/hexagon-purus-asa-results-for-...