Hydrogen vs Gasoline

[Uh_Clem]

I came across this in the metro section of the washingtonpost:
http://www.washingtonpost.com/wp-dyn/articles/A38168-2004Nov9.html

The new pump at the Shell station on Benning Road NE in the District doesn't look much different from the others, but it represents a new concept in automotive technology: hydrogen power.

It turns out it's only servicing a grand total of six vehicles in the District, but I guess you have to start somewhere. Then on the way home I heard on NPR that there was a small protest at the station consisting mostly of local residents. The locals were upset that it was a danger to the community and the only reason it was placed there is because the area is populated by predominantly lower income blacks.

I'm not going to speculate on the political/economic reasons for placing the hydrogen pump there but I'm wondering, is hydrogen really that dangerous? I always assumed that in the even of a serious spill gasoline was more dangerous because the fumes tend to stay close to the ground whereas hydrogen would disperse pretty quickly.

Do the protestors have a legitimate fear or do are they just thinking hydrogen=Hindenberg=BAD?

 

[epepke]

I'm not going to speculate on the political/economic reasons for placing the hydrogen pump there but I'm wondering, is hydrogen really that dangerous?

No, but people are stupid. Hydrogen isn't even explosive in the conditions you're likely to find around a filling station. It just burns, farily quietly.

Gasoline, on the other hand, can be explosive.

 

[Benguin]

Also the cars using it and delivery system will employ much better safety systems than regular petrol (gasoline).

My car runs on LPG (which is propane) ... people often try and tell me it is dangerous and assail me with urban myths about these cars blowing up. In fact, the regulations are much more stringent (Sealed fuel delivery system, safety cut off valves, bayonet mount filler) and this vehicle is much less likely to release fuel than any petrol vehicle.

If it catches fire I wouldn't want to be near it, but then I wouldn't want to be near a petrol one either ... and occupants will be long beyond help by the time the tank blows.

BTW: from memory, the main danger with hydrogen is that it burns with an invisible flame.

 

[shecky]

Interesting notes on hydrogen (and other) energy sources here. One aspect I rarely hear about is hydrogen embrittlement which would seem a serious problem in any containment system.

No, but people are stupid. Hydrogen isn't even explosive in the conditions you're likely to find around a filling station. It just burns, farily quietly.

Gasoline, on the other hand, can be explosive.

What conditions would one find hydrogen at a filling station? Gas? Liquid?

The only demonstration i ever saw was many years ago, when a hydrogen filled balloon was ignited from several feet away. The explosion was rather dramatic. I wonder how a comparable amount of gasoline (vapor, I figure) would perform?

 

[richardm]

The only demonstration i ever saw was many years ago, when a hydrogen filled balloon was ignited from several feet away. The explosion was rather dramatic. I wonder how a comparable amount of gasoline (vapor, I figure) would perform?

Well, fuel-air bombs consist of a quantity of vapour with air and an ignition source. They tend to go off with a bit of a pop. If I was living next door to a petrol station I wouldn't be more worried by having a hydrogen tank on the premises.

 

[Soapy Sam]

An explosion is just very rapid burning.
Burning is rapid oxidisation.
Anything that can oxidise can explode , under the right conditions.

Hydrogen can oxidise.

Discuss.

 

[Benguin]

sawdust and grain can both cause cracking explosions, given the right set of circumstance.

 

[Drooper]

During severe bush fires in Australia, Eucalyptus trees can supposedly explode, due to the combustible gases they tend to emit.

So don't go near gum trees.

 

[Benguin]

During severe bush fires in Australia, Eucalyptus trees can supposedly explode, due to the combustible gases they tend to emit.

So don't go near gum trees.

Do you think if this spread around enough some over-exuberant dimwit of an official will start campaigning for each tree to have a 'no mobile phones' sign tacked onto every tree?

 

[drkitten]

An explosion is just very rapid burning.
Burning is rapid oxidisation.
Anything that can oxidise can explode , under the right conditions.

Hydrogen can oxidise.

Discuss.

Yeah. That phrase "under the right conditions" hides a multitude of sins; I've seen steel explode, but I'm not worried about the I-beams in the building.

What kind of conditions are they using for hydrogen storage?

 

[Drooper]

Do you think if this spread around enough some over-exuberant dimwit of an official will start campaigning for each tree to have a 'no mobile phones' sign tacked onto every tree?

Well, you can't be too safe can you?

 

[richardm]

sawdust and grain can both cause cracking explosions, given the right set of circumstance.

Indeed. There is more than one distillery that's gone sky-high, back in the days when they used to mill their own barley. Get a bit of grit mixed in with the grist, and the rollers could cause it to spark - bam. Not a good thing when there's barrels of spirit lying around the place.

 

[Anders W. Bonde]

IIRC, hydrogen is also odorless, making leaks difficult to detect 'at a sniff'. I suppose a scent could be added to it, and perhaps also something to make the flame visible if need be. Invisible flame is also an issue for methanol powered vehicles.

I haven't followed the developments i hydrogen fuel for automotive purposes closely, but off-hand it seems like a very good idea: Endless supplies, can be hydrolized using renewable power sources such as solar power, hydroelctric power, wave power, aerogenerators etc., or it can be made from vegetation, and it's very clean as the only byproduct of its combustion is water vapor, which, if necessary, can even be condensed so that it can be released back to the environment in a location remote from the source if need be. However, I'm not sure whether water vapor is a 'green house effect' gas - but it would certainly enable reduction of carbondioxide emissions. Still, there may be an issue with nitrous oxides? - the engine breathes more nitrogen than oxygen.

It seems the major challenge is being able to store enough of the gas in a simple, safe, cheap and compact way in a vehicle - isn't mileage on a tank a bit short at present?

Oh, well, this thread has fed my curiosity so I'm going to have to start some Googling on hydrogen powered vehicle technology...

 

[wollery]

However, I'm not sure whether water vapor is a 'green house effect' gas - but it would certainly enable reduction of carbondioxide emissions.

Water vapour does have a small greenhouse effect, but considering how much there already is in the atmosphere and how much more efficient CO2 is as a greenhouse gas, I don't think that we'd have to worry on that score.

 

[DaveW]

Re: Re: Hydrogen vs Gasoline

No, but people are stupid. Hydrogen isn't even explosive in the conditions you're likely to find around a filling station. It just burns, farily quietly.

Gasoline, on the other hand, can be explosive.

I don't know what conditions you are thinking of, but, in general, Hydrogen is rather dangerous in concentration: Hydrogen Dangers

Gasoline can be explosive, true, but, in the everyday use, you have to atomize it, compress it, and spark it to make it explode.

 

[shecky]

Well, fuel-air bombs consist of a quantity of vapour with air and an ignition source. They tend to go off with a bit of a pop. If I was living next door to a petrol station I wouldn't be more worried by having a hydrogen tank on the premises.

Point is, hydrogen has a wider flammability range, at 4% to 74%, than gasoline at 1.4% to 7.6%.

And how is the fuel dispensed? Liquid? Compressed gas?

Problems with diffusion through common materials and metal embrittlement, both which can cause leaks and/or catastrophioc failure. This is something I rarely hear mentioned regarding hydrogen.

While I have no doubt that the filling station mentioned is probably safe enough. I suspect chances of hydrogen leak or spill are small. However, relatively few know how to deal with such a event.

 

[shecky]

I haven't followed the developments i hydrogen fuel for automotive purposes closely, but off-hand it seems like a very good idea: Endless supplies, can be hydrolized using renewable power sources such as solar power, hydroelctric power, wave power, aerogenerators etc., or it can be made from vegetation, and it's very clean as the only byproduct of its combustion is water vapor, which, if necessary, can even be condensed so that it can be released back to the environment in a location remote from the source if need be. However, I'm not sure whether water vapor is a 'green house effect' gas - but it would certainly enable reduction of carbondioxide emissions. Still, there may be an issue with nitrous oxides? - the engine breathes more nitrogen than oxygen.

It seems the major challenge is being able to store enough of the gas in a simple, safe, cheap and compact way in a vehicle - isn't mileage on a tank a bit short at present?

AFAIK, one of the biggest problems is cost. As of yet, cost effective hydrogen for the masses doesn't seem a viability. While there's a virtual limitless supply possible, it comes at a net BTU loss via other energy sources. Electrolysis (probably the most efficient way of making hydrogen) is terribly inefficient. In effect, hydrogen won't be working for you, you'll be working for the hydrogen. Plain old petroleum fuel, with still plentiful natural sources, outshines forseeable hydrogen by quite a bit.

This isn't to say there isn't a place for hydrogen powered internal combustion engines. But practical applications are justified in relatively rare conditions, such as warehouse use where exhaust can be a hazard.

 

[Uh_Clem]

Thanks for all the good info folks!

 

[jj]

Point is, hydrogen has a wider flammability range, at 4% to 74%, than gasoline at 1.4% to 7.6%.

Yeah, but released, it tends to go UP fast, and dilute itself, rather than pool vapors at ground level.

I would, though, worry about hydrogen embrittlement. I've seen it in old gas pipes (that used "manufactured gas" among other things, which is a mix of H2 and CO) and it's pretty amazing, you can crack some of those pipes with a very small hammer, without a hard swing.

 

[kookbreaker]

IThe only demonstration i ever saw was many years ago, when a hydrogen filled balloon was ignited from several feet away. The explosion was rather dramatic. I wonder how a comparable amount of gasoline (vapor, I figure) would perform?

I used to do that hydrogen baloon explosion for my museum outreach program. It was impressive. It was more impressive if you added Oxygen (bad adding some of your breath) to the mixture in the baloon.

Gasoline would not ignite in the same manner since it also requires oxygen. That's why cars have carboraors or Fuel Injectors. The joy of gasoline is that it will burn on the surface (where it evaporates and mixes with the air) so some of it can land on you while its burning for some real fun.

I am amused by those who think hydrogen is the most dangerous thing in the universe, yet happily pour a liquid ten times more dangerous into their vehicles every other day.