WRC mainclass from 2027

[Steve Boyd]

Hydrogen-powered Hyundai rally car now being driven by Hayden Paddon in NZ...

https://www.facebook.com/HyundaiNZ/v...40aB7S9Ucbxw6v

If you study the video closely, you'll see that the car isn't powered directly by hydrogen - it's a conventional battery electric vehicle. The hydrogen fuel cell is used in the re-charging station that provides the power to re-charge the car battery.

Except it's not true. Hydrogen is pretty safe. With hydrogen in open spaces you vitrually can't ever get a vapor explosion or self ignition. The reason is that unlike gasoline, methan etc. it is far ligher than air and therefopre never concentrates in an open space. When it's leaking it just dissipates in the air and nothing happens. It also requires far richer (and virtually impossible in open space) concentration for self ignition than gasoline vapors. Plus unlike gasoline or battries it's not toxic.

Of course you can't shoot the pressurized tank but you can't do that with petrol tank or a battery either.

The flammability range for a mixture of hydrogen in air is 4% to 75% by volume - one of the largest ranges of any flammable mixture.
Details of how you ensure that the risk of a explosion from a release is minimised is covered in EN IEC 60079-10 Classification of areas - Explosive gas atmospheres.

But volatile or not, you still need to ignite it, right? The reports of investigations into that Norway explosion do not explain what that ignition was. One article says "This [incorrectly installed] valve leaked hydrogen which caught fire when it came into contact with the air."

If there's a hydrogen leak there will be a volume where the mixture of hydrogen and air is within the flammable range. If that volume coincides with a source of ignition then there will be an explosion. Note that hydrogen/air mixtures have one of the lowest ignition energies of any flammable mixture - 0.02 mJ. A hot surface or a spark with more energy than this could ignite the mixture. This is why the design rules for electical equipment for use with hydrogen are the most stringent of any of the equipment groups. A substantial leak from an incorrectly installed valve could well cause a large cloud that came in contact with a light switch, electric motor, incadescent lamp, mobile phone &c &c. The Piper Alpha oil rig disaster was caused by a "plumbing" error, so it isn't just hydrogen that's a problem.