Toyota is introducing a prototype hydrogen-powered vehicle.
Here is a video of the Hindenburg disaster.
What prevents a fuel-cell vehicle from exploding spectacularly if something goes wrong?
Well for one thing, it is being used as a combustible fuel, not as a buoyancy device, so it is treated with much more respect. And for another, there isn’t nearly as much hydrogen in a fuel cell as there was in the Hindenburg.
The biggest problem with hydrogen fuel cells is generating the free hydrogen. It takes a lot of energy to strip hydrogen atoms from water, so you really aren’t liberating any net amount of energy in the process. You are just transferring energy from some other location (such as a nuke plant) where the hydrogen is stripped, and then using it in the vehicle.
Hindenburg didn’t have the hydrogen stored in a strong and tough fuel tank, did it ? why compare the two ?
Petrol/Gasoline explodes spectacularly when the fuel tank is burst and the fuel is exposed to a flame (eg brake fluid ignites on the exhaust manifold) or spark.
Same with hydrogen. Its stored in a tank. The tank is meant to be sufficiently strong and tough to keep things relatively safe. If the hydrogen leaks out all at once, it can go off spectacularly.
It’s actually very difficult to get hydrogen to explode. It’ll burn, sure, and fairly quickly, but it’s also rising away from the source while it’s burning, and so does very little damage. The problem with the Hindenburg wasn’t that the hydrogen was burning; it was the envelope. The envelope of the Hindenburg was treated with a substance that is basically thermite, which behaved about how you’d expect thermite to behave.
I suppose so. Hydrogen is apparently more energy-dense than gasoline, so if it does go off, even only a few times per million, it could be pretty bad. Ev batteries, AFAIK, will burn but don’t explode.
I can’t imagine enough oxygen in the air becoming available to so much compressed hydrogen to turn it into a chemical explosive.
If anything, it’ll just be a moderate pressure bomb… On fire. Kinda.
You’ll be fine. I think.
Not really. Gasoline needs an oxygen source to burn, hence the need for carburetors and fuel injectors. It will not explode but will instead burn when the tank is ruptured. Granted it burns damn hot and can engulf a vehicle but it does not explode, and not even close to what you see in the movies where a car goes over a cliff and looks like 5 lbs. of C4 in the trunk just went off.
Good man, exactly what I dropped in to say. 
No. Not at normal atmospheric temperatures and pressures. Petroleum is a fluid and magnitudes denser than hydrogen which is a gas. It is possible to compress H to a liquid but there are engineering problems for everyday use.
What. We’re talking about 11 lbs. of compressed hydrogen in a passenger-vehicle sized tank. If that thing crashes into, say, an interstate pylon and is punctured, you’ve got a jet of flammable gas. If there is a spark, doesn’t that make a terrible mess?
And even then the disaster was a lot less lethal than you’d expect for something so spectacular. Hydrogen fires I understand are less lethal than they look because the heat & flames from them tends to go straight up, due to hydrogen being so light. Unlike liquid fuels, which stay on the ground and spread as they burn.
Actually I’d think that hydrogen-fueled cars would be potentially dangerous not because they carry hydrogen, but because they carry it under pressure. In an accident I’d be less worried about fire than I would about being shredded by shrapnel from a burst tank.
[ nitpick]Fuel cells do not work on combustion.[/ nitpick]
Is it inherently worse than a widening pool of flammable gasoline, from a punctured gas tank? Hydrogen, at least, will dissipate faster in an open air environment.
The same thing that prevented the Hindenburg from exploding. The hydrogen isn’t mixed with air.
The Hindenburg may be a huge fire, but there’s no “boom, bits being blown outwards”.
For the pressurized hydrogen to explode particularly one of the following scenarios have to happen:
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The pressure tank has to be so catastrophically badly constructed that it ruptures instantly and releases all the hydrogen in one boom. I’m fairly confident the designers will avoid that.
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The hydrogen has to leak into a confined space at a rate higher than it leaks out, and hydrogen leaks out of practically anything. Then you need a spark in that confined space. I’m fairly confident the designers can find a way to avoid that.
Any non-catastrophic leak in the hydrogen system will give a nasty, but localised fire. Unlike petrol hydrogen goes up, up, up really fast. No pooling and evaporating to explode the way even petrol doesn’t do unless you hollywoodize it.
Is it just paranoia then that makes the people who operate road tunnels very wary of vehicles powered by, or carrying flammable gas?
http://www.eurotunnel.com/uploadedImages/resources/site-information/Acceptability-of-vehicles-UK.jpg
Well for one thing the text accompanying that table mentions LPG and equivalent flammable gas. LPG is heavier than air and although natural gas is lighter, it’s nowhere near as light as hydrogen.
Next, the eurotunnel is not a road tunnel. The restrictions are on what vehicles may be loaded on the train travelling the tunnel.
Probably what they’re worried about is a slow leak that produces the correct mixture of oxygen and fuel for a big bang event. The same reason you don’t store your propane tank in the garage or a petrol tank below decks in a boat.
Hydrogen has an extremely high energy content per mass, but it’s really tough to beat liquid hydrocarbons like gasoline for energy content per volume. For a car, the volume is usually more relevant, hence why we use gasoline for them.
I don’t feel like there is a consensus.
-I can see that not building the fuel tank out of a thermite-like substance is a step toward avoiding Hindenburg-like results.
-I understand that the hydrogen would need enough oxygen to combust, and that it’s buoyancy would cause it to float upwards.
Still, we are talking about pressurized, flammable gas. And I can see the buoyancy of hydrogen causing it to come into contact with all the oxygen it needs to combust quickly, instead of just sitting there in an air-excluding liquid form like gasoline. In an accident, isn’t there the potential to burn a whole lot of hydrogen really, really fast, possibly in a way that might as well be an explosion?
Of course it’s theoretically possible, just as it’s possible for your gas tank to rupture in an accident and create a big puddle of flaming gasoline under your car. But they take precautions to prevent that.
http://automobiles.honda.com/fcx-clarity/hydrogen-safety.aspx