Danger of hydrogen

[Moontanman]

Is anyone aware of the danger that hydrogen use is setting us up for? Yes hydrogen is the best fuel in terms of pollution and avoiding the greenhouse effect but did you know that hydrogen will destroy the ozone layer? Yes hydrogen is much worse than CFC's at destroying the ozone layer. Any use of hydrogen as a fuel means lots of hydrogen being released as fuel is dispensed into cars and other vehicles. Hydrogen rises immediately to the ozone layer and reacts with ozone to produce oxygen and water. It is a very bad thing when you think of all the damage done by CFC's using something that is far worse doesn't look like the ideal thing to do.

 

Michael

[freeztar]

I didn't know that. I still don't know that.

Can you back up your claim?

 

Hydrogen fuel cells react H with O2 to produce water and electricity, neither of which destroy ozone.

Hydrogen vehicle - Wikipedia, the free encyclopedia

Ozone - Wikipedia, the free encyclopedia

[Moontanman]

I didn't know that. I still don't know that. ;)

Can you back up your claim?

 

Hydrogen fuel cells react H with O2 to produce water and electricity, neither of which destroy ozone.

Hydrogen vehicle - Wikipedia, the free encyclopedia

Ozone - Wikipedia, the free encyclopedia

 

Yes I can, it's not the hydrogen inside the vehicle that causes problems but the estemated 10 to 20 percent that escapes during processing and refueling. This hydrogen rises up to the ozone layer and reacts with ozone to make oxygen and water. Hydrogen Poses Risks to Ozone Layer; Atmospheric Mercury Declining; Where Have All the Flowers Gone?,

Hydrogen Fuel May Disturb Ozone Layer AP 12jun03, these links should give you some idea of what i am talking about. it's almost funny that the one thing that is supposed to save the planet could actually makes things worse.

 

Michael

[freeztar]

First of all, I find the 10-20% to be not only a very broad range for such a scientific statement, but also incredulous.

 

There is no reason that pipes need to leak. Consider the amount of natural gas traveling underground in the US. Leaks happen, but are relatively minor in effect.

 

Sinks

 

A major sink of hydrogen gas is soil uptake. The amount of hydrogen in different locations around the world has been measured since 1989. There are seasonal variations in the amount of hydrogen in the atmosphere, and the measurements have shown that the Northern Hemisphere has a lower H2 minimum than the Southern Hemisphere. This reflects the greater area of land in the Northern Hemisphere. Another hydrogen sink is the formation of water from hydrogen gas and hydroxyl radicals:

 

H2 + OH → H2O + H

 

hydrogen molecule

 

This reaction accounts for the removal of around 20 Tg H2/year.

Hydrogen Economy

 

I contest that the same reactive properties that might make H2 dangerous are the same properties that might aid in preventing mass escape. This might be accomplished by hydroxyl reactions at source (kinda like emergency sprinklers).

[Zythryn]

...Yes hydrogen is the best fuel in terms of pollution and avoiding the greenhouse effect...

 

Not to take this too off topic, hydrogen is NOT the best fuel for automobiles. Perhaps for semi trucks or other large vehicles, but not for standard automobiles.

Typically to create hydrogen you use electricity. This is not a 100% conversion. Rather than add a level of energy loss, just use the electricity to power the car. That is the best fuel in terms of pollution and avoiding the greenhouse effect.

Regarding the dangers of hydrogen, I am skeptical it is more of a threat that sources other than electricity. However, if it is, that is just one more reason for not bothering with Hydrogen and just stick with electric cars.

[CraigD]

… but did you know that hydrogen will destroy the ozone layer? Yes hydrogen is much worse than CFC's at destroying the ozone layer. Any use of hydrogen as a fuel means lots of hydrogen being released as fuel is dispensed into cars and other vehicles.

I think this is a severe oversimplification, and a premature conclusion.

 

Hydrogen, being much lighter than CFCs, seems more likely to reach the stratospheric ozone (O3) layer. However, unlike hydrogen, CFCs are not reagents, but catalyst, in ozone-depleting reactions. Even at very low gas density, a single CFC molecule can release chlorine to catalyize the elimination of hundreds of thousands of ozone molecules over a period of about 100 years. (source Ozone depletion - Wikipedia, the free encyclopedia).

 

Hydrogen must have a concentration of at least 4% by volume to react (burn) with oxygen (O2 or O3), and requires a temperature of 585° C to begin (ignite) this highly exothermic reaction. (source: HyWeb: Knowledge - Hydrogen in the Energy Sector Chapter 2) The average concentration of hydrogen by volume in the atmosphere is about 0.00006%. In other words, hydrogen wouldn’t just deplete ozone, it would have to be concentrated, sparked, and burned .

 

Hydrogen is also very reactive, so how much hydrogen would reach the stratosphere before bonding with heavy molecules in the lower atmosphere is (in the context of this thread up to this post) an unconsidered question.

Hydrogen Poses Risks to Ozone Layer; Atmospheric Mercury Declining; Where Have All the Flowers Gone?, Hydrogen Fuel May Disturb Ozone Layer AP 12jun03

Note that the researchers quoted in these articles note that their conclusions are preliminary and speculative.

it's almost funny that the one thing that is supposed to save the planet could actually makes things worse.

That would be ironic. Hopefully, it will not prove to be true.

 

I think it’s very important for research into the effects of increased released hydrogen on the atmosphere to continue, resulting in reliable models and confident predictions. At present, however, I consider it premature to treat it as a certain threat.

[Moontanman]

I agree it is too soon to brand hydrogen a certain threat but to dismiss might be too optimistic as well. Hydrogen doesn't have to burn to react with ozone it will react with ozone on contact and with oxygen in the presence of light. No fire of any temp is necessary. Hydrogen is a very difficult gas to contain. It will diffuse right through most materials even metals. Of course various materials will permit diffusion at various speeds. The leakage is both from refueling cars all the way back to the manufacturing process. Not only will it react with ozone it will also cause cooling of the upper atmosphere through cloud development. I'm not certain of how much of threat it will be but it most certainly needs to be looked at before we are dependant on hydrogen as fuel. I am puzzled by why hydrogen isn't appropriate for cars but is for large trucks?

 

Michael

[CraigD]

I agree it is too soon to brand hydrogen a certain threat but to dismiss might be too optimistic as well.

I agree

Hydrogen doesn't have to burn to react with ozone it will react with ozone on contact and with oxygen in the presence of light.

:QuestionM Can you describe one or more of these reactions in detail? (I’m not arguing that they don’t exist, but my chemistry is too weak for me to confirm or deny it) Hydrogen can, I know, react spontaneously with oxidizers such as chlorine and florine, or with nitrogen when catalyzed by elements such as iridium. This latter scheme is used for small, reliable, hydrazine-fueled rocket motors, such as those used in the reaction control system of many spacecraft.

No fire of any temp is necessary.

Though possibly it’s not necessary for ignition, I can’t think of any other word to describe the intensely exothermic reaction of hydrogen and oxygen as anything but “fire” – 10[math]^{-19}[/math] Joules/hydrogen atom is a lot (source: Hydrogen - Wikipedia, the free encyclopedia)

Hydrogen is a very difficult gas to contain. It will diffuse right through most materials even metals. Of course various materials will permit diffusion at various speeds. The leakage is both from refueling cars all the way back to the manufacturing process.

Very true, I agree. The 10-20% loss suggested by the articles strike me as very reasonable estimates.

Not only will it react with ozone it will also cause cooling of the upper atmosphere through cloud development.

More complicated factors, pointing out, I think, the need for more research and a very good atmospheric model

I'm not certain of how much of threat it will be but it most certainly needs to be looked at before we are dependant on hydrogen as fuel.

I agree emphatically.

I am puzzled by why hydrogen isn't appropriate for cars but is for large trucks?

I’m pretty sure (for the first time in this thread!) that this is because the mass/power and volume/power ratios of truck are much higher than those of cars. A major problem with hydrogen as a fuel is energy density. Current best hydrogen storage systems are about 3 times less dense than alcohol and fossil fuel systems.

 

We were just discussing this in ”Hydrogen fuel cell issues” and the posts leading up to it.

[Zythryn]

I am puzzled by why hydrogen isn't appropriate for cars but is for large trucks?

 

It isn't so much that hydrogen isn't appropriate for cars. It is that electricity is a better source of power for cars.

However, due to sheer size I don't believe batteries can supply the power needed to move big-rigs with current technology. And in that case, hydrogen is the next best.

[Pyrotex]

...Hydrogen rises immediately to the ozone layer and reacts with ozone to produce oxygen and water. ...

In my opinion, this is probably bogus. One, hydrogen will not "immediately" rise to the ozone layer which is in the stratosphere. Diffusion from sea level would take days if not weeks for any appreciable fraction to reach those altitudes.

 

Two, hydrogen "burns" so easily in the presence of oxygen, that little if any would be left after a few days. Typically, all it takes is one UV photon to excite an H2 molecule enough to combine with any O2 molecule near by. Since 22% of our atmosphere is O2, the average H2 molecule will be oxidized after fewer than a dozen UV photons.