Thread: Problems With Hydrogen

On another thread recently, I had noted that releases of hydrogen would not persist for long in the open air due to the fact that this gas is lighter than air and would disperse accordingly. Delving deeper into the subject, I found that hydrogen burns under an exceptionally wide range of concentrations, 4% to75%, vs. 5.3% to 15% for methane. Hydrogen flames also propagate more rapidly in enclosed volumes of space, hence there is greater risk of explosion compared to other flammable gases, and will ignite with a very weak spark- all of this making special safety precautions necessary.

Hydrogen is odorless and burns with a very pale, almost invisible flame(this last consideration is of course immaterial in the event of explosion) and adding odorants and/or chemicals which would make the flame more evident will ruin the gas for use in fuel cells and further dilute the already low energy per unit volume of the gas.

Hydrogen embrittles many metals and is incompatible with existing natural gas pipelines, is less than a third the energy density of gasoline per unit volume even when in liquid form(at or below H2 boiling point of -422.8 *F/-252.8*C) and requires a great deal of electricity to produce via electrolysis of water using current technology.

Given all this, the prospect of the widely touted "Hydrogen Economy" coming into being seems remote.

Can you suggest another fuel? A sustainable fuel?


I'll answer safety and try the others later.

One thing about hydrogen gas it does for safety, like no other, is it gets the hell away from you, fast. It excels at leaking away and dispersing. Gases like propane will fill a basement, asphyxiate the victim before demolishing the house. Gasoline of course will puddle and splatter. Hydrogen shoots to the sky, whether burning or not (people are rarely in the sky). While many other fuels have been weaponized, hydrogen is least suited to killing and destruction. Military thumbs down = civilian thumbs up.

Yes, hydrogen is safe... <cough>Hindenburg<cough>

Originally Posted by Pong

Can you suggest another fuel? A sustainable fuel?


I'll answer safety and try the others later.

One thing about hydrogen gas it does for safety, like no other, is it gets the hell away from you, fast. It excels at leaking away and dispersing. Gases like propane will fill a basement, asphyxiate the victim before demolishing the house. Gasoline of course will puddle and splatter. Hydrogen shoots to the sky, whether burning or not (people are rarely in the sky). While many other fuels have been weaponized, hydrogen is least suited to killing and destruction. Military thumbs down = civilian thumbs up.

I believe I mentioned this much in the first sentence, but thank you both for responding. As for the case of the Hindenburg, the infamous film of its demise shows clearly visible flames, probably not solely the result of hydrogen combustion. Nor was hydrogen used as fuel, the engines ran on diesel fuel.

Correct. Most casualties were attributed to diesel, which sticks to clothes and skin, and falling/jumping.

Obviously a vehicle's hydrogen fuel tanks would be positioned to minimize harm in case of leak or explosion, just as conventional tanks are today. I imagine ceiling vents would be mandatory in all parking areas.

I think that people can learn hydrogen's particular dangers and handle it safely in everyday life, as with electricity or gas stoves.



The relatively low energy density of liquified hydrogen is a shame. One must lug larger tanks, or refuel more often.


Embrittlement is minor, easily solved issue I think, because the surfaces in a hydrogen/air combustion engine actually in contact with fuel are few and small. Well you certainly don't need a lot of post-combustion parts, whereas today's mufflers embrittle and require frequent replacement due to hydrogen (among other things) in the exhaust.


The electrical cost of producing hydrogen fuel is too high... if you weigh that in Texas. If you have 3,000 km of unexploited hydroelectric potential (unexploited for lack of local energy consumers) then it may be worthwhile. Indeed it may be the only way to bring real investment to some underdeveloped regions.

Storing and handling hydrogen is close to impossible. It is certainly a very impractical fuel. However, there is a better way.

Assuming hydrogen can be manufactured reasonably cheaply, it can be immediately converted to methane, by reaction with CO2. Methane is a clean burning fuel that is much more easily stored and handled. The methane in turn, can be converted to liquid hydrocarbons, like petrol, if that is required, and this can be used in a modern car with no conversion.

The only real problem with this, is that making the hydrogen in the first place is energy intensive, and hence costly.

Sorry about the double post, but I realised I had forgotten to add another technology for using hydrogen.

If you take biomass - like forest industry waste - and heat it in the absence of oxygen (anaerobic pyrrolysis) - it splits into solid charcoal and volatile organic compounds. If those organic compounds are mixed with hydrogen gas and passed over a suitable heated catalyst, hydrocarbons are formed, which can be refined into petrol for automobile fuel.

The charcoal left behind can be plowed into soils by the terra preta system to both improve soils and to work against global warming.
Terra preta - Wikipedia, the free encyclopedia

I think that the "low energy density" of Hydrogen needs to be challenged. I had heard just exactly the opposit, that hydrogen was the most energetic possible fuel.

The Hindenberg was painted with iron oxide primer then a finish coat of shiny silver paint which use powdered metalic aluminum as the pigment. This mixture has another name, "thermite" and is used in incendiary devices. Thermite burns very rapidly, at a high temperature, without the need for atmospheric oxygen. In short the Hindenberg was a flying bomb with the explosive on its skin. Filling it with helium would not have saved it.

Finaly, the storage problem has been addressed with the use of metal hydride sponge filled tanks. Using them hydrogen can be stored at much lower pressures.

There do still exist problems with hydrogen's high difusablity, it will seep through joints and materials that heavier gasses are not able to penetrate. Higher engineering standards are required.

Originally Posted by Pong

Can you suggest another fuel? A sustainable fuel?

Yeah. Methanol.

http://en.wikipedia.org/wiki/Methanol_economy

http://en.wikipedia.org/wiki/Methanol_fuel

Similar to hydrogen, you can synthesize it by combining water and CO2 from the air. When you burn it, it releases the CO2 back, but if we captured CO2 to produce it then that just means we're breaking even on carbon emissions.

It has one other really big advantage. You can burn it in an ordinary gasoline engine. The only modification is to make sure certain metals aren't present in the fuel line. Otherwise it's safe for use in existing automobiles. In fact, safer than gasoline, because it's harder to ignite in the event of an accident. The down side is it only has 1/2 the volume - to - energy ratio of gasoline, so you'd have to fill your tank more often.

We can store Hydrogen in solid metals. This is more safe & compact compared to gas/liquid storage because all the Hydrogen are atomically (strongly) bonded to the metal atoms (only to be released after heating for example), like a sponge. One material that I've heard is 'Metal Hydride' (other material is possible but might have unfavourable properties; like releasing too quickly or 1 time use or not good absorbing or need high temperature), and there's Alkali Metals (Sodium Silicate) that release Hydrogen when in contact with water; which could provide Hydrogen for fuel.


eg:
New metal hydride clusters provide insights into hydrogen storage ;Metal Hydride
Researchers discover promising hydrogen storage material ;somekind of material called Phthalocyanines
Hydrogen cartridges fuel laptops and phones for outdoor enthusiasts ;Alkaline Metal