Naked Science Forum
Non Life Sciences => Technology => Topic started by: Jessica H on 31/10/2010 03:21:24
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Hydrogen gas is so explosive that I'm wondering how they can engineer a hydrogen fuel cell powered car to be safe. Am I misunderstanding that there is actually a tank full of hydrogen in these cars?
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Hydrogen gas is so explosive that I'm wondering how they can engineer a hydrogen fuel cell powered car to be safe. Am I misunderstanding that there is actually a tank full of hydrogen in these cars?
First of all, I would not be too concerned. Hydrogen fuel cell vehicles have been "just around the corner" for more than fifty years. I was reading about their imminent arrival when I was in my early teens. I'm still waiting [;D]
There are other possible hydrogen based fuels for fuel cells, but assuming we are talking about a pure hydrogen fuel cell vehicle, the hydrogen would be in liquid form. Like most fuels, as long as it is not mixed with a source of oxygen, like air for example, it will not burn. If it cannot burn, it will not explode.
If the hydrogen tank in a vehicle were to rupture for some reason, the liquid hydrogen would absorb a large amount of heat from the atmosphere and turn into hydrogen gas. However, hydrogen gas is the lowest density thing around, so it will immediately "leave the area" and head for the clouds. This might result in a fireball in the sky, but, arguably, it should be a lot less dangerous than a pool of burning liquid gasoline.
Poor old hydrogen has been getting a really bad rap ever since the Hindenburg went down and traumatized the World. However, if you look at the footage of that event, you'll see that the airship did not explode. It simply burned up.
There is a fair amount of evidence that the fire had little to do with the hydrogen and that it had a lot more to do with the flammable materials used in the construction of the airship.
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Roughly twice as many survived the Hindenburg disaster as were killed by it. I think that's better than the odds in a modern plane crash.
Any source of energy- a fuel tank, a battery or whatever is potentially dangerous.
Gasoline was initially a dangerous by-product of the oil industry. It was considered too flammable to use- then came the internal combustion engine.
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The fuel cell is not the worry, it is the Hydrogen itself. It will diffuse though any material, at least if not stored at cryogenic temperatures, and has the unfortunate byproduct of making anything it comes into contact with brittle over time. Thus hoses, fixtures and tanks need to be replaced regularly, and have a much shorter life than the fatigue life they normally have. Much better is to store the Hydrogen as a chemical like methane, ethane or as an alcohol. Slightly lower energy, but much easier to store, and a lot easier to handle and transport. As a bonus you can use some existing engine designs with little modification to combust it.
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Nitrogen is in huge amount in our environment.I really think that it very useful for the normal use of people.The problem is that it has to be stored in cryogenic temperatures. without them its very harmful .It will save our limited resources but ,main emphases has to be on its preservation.
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The safe storing of hydrogen for vehicles is most likely to become a commercial reality by means of some form of chemical adsorption, within a 'tank' containing a chemical matrix that can take-up the H2.
http://en.wikipedia.org/wiki/Hydrogen_storage#Physical_storage
- Carbon nanotubes, Metal-organic frameworks, etc
http://en.wikipedia.org/wiki/Adsorption
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What is preventing H2 becoming a practical reality for consumer vehicles?
Is it the lack of infrastructure - preventing mass scale up and the economies of scale that come with it?
Is it the inefficiencies of converting energy to another form to create the hydrogen?
Is it cost and safety aspects of storage?
Is it mechanical limitations with the vehicles? Poor performance? mpg? operating speeds?
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My guess is that it is all of the above.
Right now we are in a global energy deficit, in which fossil fuels are a cheap fuel source, and we have not captured sufficient renewable resources to replace the use of fossil fuels.
Using fossil fuels to create hydrogen to fuel a car is less efficient than using the fossil fuels directly to fuel a car.
If one created a "clean" energy source such as a windmill to generate hydrogen for one's personal car, that's great, but it would be more efficient overall to feed that electricity into the power grid, and displace coal that is being used to heat homes and as industrial energy.
Of course, there are issues with local vs non-local energy sources, so there would be benefits if a country such as Iceland chose to use 100% local energy sources rather than importing fossil fuels.