Hydrogen Fuel Cell Containers

[Burrido]

Read in a recent Car and Driver magazine (or was it Road and Track??) about Hydrogen Fuel Cell cars of the future. The thing that puzzled me is that they stated that the containers for the hydrogen fuel would either have to be cylinderical or doughnut shaped. I can understand a cylinderical fuel tank, but a doughnut shaped one? Any answers are appreciated.

[Tuckerfan]

Simply put, it's a bitch to try and pump pressurized liquids into anything that's not round, and a donut shape allows one to enjoy the benefits of a cylinder, without the long length.

[Padeye]

A sphere doesn't have the length of a cylinder but won't fit in a flat space like a toroid shaped tank. Could easily be fitted to a spare tire compartment.

Considering that fact, do any LP or natural gas tanks for vehicles have a donut shape? All I have ever seen is a short cylinder?

[Roches]

It's possible that hydrogen cars will carry gaseous hydrogen under pressure. Hydrogen is flammable, of course, and there are some safety risks involved with using gaseous hydrogen, but IIRC it is not substantially more dangerous than gasoline. But gaseous hydrogen is not the only possibility. Hydrogen cars may carry their fuel adsorbed on or combined with some carrier material. One possibility I've read about is using titanium (or other metal) hydrides to reversibly bind the hydrogen until it's needed. This is actually more efficient than gaseous hydrogen, and much safer. Another possibility would be to generate the hydrogen in situ from methanol or natural gas. Small fuel cells for personal electronic devices are very likely to use methanol 'fuel packs' rather than gaseous hydrogen, and cars that generate hydrogen from another fuel would be an important stopgap until hydrogen fuel stations become common.