A page of energy issues partly but not completely obsoleted by myths of Hydrogen
I'm a fan of Quora and spend sometimes even more time there than at Wikipedia.
One question that comes up regularly is "Why isn't Hydrogen used for..." Just fill in the predicate!
So rather than keep repeating the much the same answers, I've set up this page and will in future just link to it.
Risks
Explosions
When a flammable gas is mixed with air, there are three possibilities. See Flammability_limit at Wikipedia.
If the gas/air mixture is rich enough in the gas, the mixture will burn in air when ignited. A little air doesn't hurt.
If the gas/air mixture is rich enough in air, then the mixture will still support combustion like air. A little gas doesn't hurt.
Between these two extremes there is a range of mixtures that are explosive. These are obviously to be avoided!
Of all industrial gases, the one with the greatest range of explosive mixtures when mixed with air is Hydrogen.
Leaks
Hydrogen has the lightest molecular weight of all gases, and the smallest molecular radius.
The small molecular weight means that at any given temperature, its molecules are travelling very fast. That combined with their small size means that they will leak through cracks that other gasses would find impassable.
And such cracks are made more likely by hydrogen embrittlement, see below.
Detection
Hydrogen is odourless, tasteless and colourless.
LPG has the same problem. Both Butane and Propane are odourless, tasteless and colourless. But there are many nasty-smelling gases that are cheap and which in small quatities don't affect the usefulness of LPG, and so LPG is in most parts of the world required by law to be tagged with an "odorant", something you can smell, see EN 589 for the most common standard. Leaks are then more easily detected. And in the days when town gas supplies were syngas, this was similarly tagged with an odorant. This didn't address pure Hydrogen leaks but did address what was seen as the more deadly problem, that of leaks of poisonous carbon monoxide.
So with both LPG and town gas, it's generally seen as sufficiently important to be able to smell the stuff that it's required by law to tag it with something smelly. Hydrogen is a lot more dangerous than LPG, and arguably more dangerous than town gas.
But tagging doesn't work with Hydrogen. If you tag it with another gas that is easier to detect, when it leaks out it just leaves that other gas behind.
Hydrogen gas detectors do exist, see Hydrogen_sensor at Wikipedia. And Hydrogen isn't poisonous like the carbon monoxide in some town gas. So it's not all bad news. Just almost all.
Embrittlement
Contact with Hydrogen makes many metals brittle. See Hydrogen_embrittlement at Wikipedia. Brittle metal cracks easily. So there are lots of cracks through which the Hydrogen can leak. See above.
Myths
Why are these questions so prevalent? One reason is probably the proposed Hydrogen_economy which still has its advocates. Hydrogen does have applications, such as a growing use in powering forklifts, and even some of those predicted many years ago. It's not a new idea!
Hydrogen as an energy source
This is the myth that really makes you wonder!
There are no Hydrogen wells. There may be shortly but discovery of natural Hydrogen deposits is a recent development, and one field is proposed for development. See https://www.researchgate.net/publication/327872713_Discovery_of_a_large_accumulation_of_natural_hydrogen_in_Bourakebougou_Mali for the position as of 2018.
Hydrogen can be used to distribute energy, but that energy currently needs to come from some other source... currently fossil fuel.
So currently at least Hydrogen is not an energy source and never was in the past.
And actually this is a very useful thing to know. People who glibly say it is an energy source are either ignorant or lying or both. Give them the benefit of the doubt, they are probably just confused by all the absolute rubbish published on energy matters! But treat the rest of what they say with this in mind.
That's not to say you should dismiss their other claims just on that basis. That would be ad_hominem of course. But neither should you take their word for anything related to energy, because they have not done their homework, and more dangerous still they seem to think they have. See the expert and the others.
That's of course unless you wish to use what they say to promote your own agendas.
Green Hydrogen
The Green Hydrogen Coalition was formed as recently as 2019.
The problem being that there is as yet no Green Hydrogen to promote. Hydrogen is currently produced by steam_reforming of methane, so in practice it's a fossil fuel, and a rather wasteful one. It's generally more efficient, a lot safer and easier, and produces less CO2 if you just use the methane as a fuel instead.
The best hope of eventually producing "Green Hydrogen" is probably a high-temperature nuclear reactor using either molten salt or liquid metal coolant. A gas coolant is also possible but less likely. The point is that no water-cooled reactor can do this... in fact when current reactors overheat, as happened at Three Mile Island and Chernobyl and Fukushima, one of the problems is (unwanted to say the least) production of Hydrogen. This was a factor in all three disasters. Hydrogen is nasty stuff.
Deliberately nuclear-produced Hydrogen is a way off yet, and probably not what that particular organisation wants to promote anyway.
Hydrogen as energy distribution and or storage
There is a program in Scotland to distribute Hydrogen to homes and other premises. See the H100 Project.
The intention is to use power from the local wind farm to produce Hydrogen by electrolysis, and convert consumers who currently use natural gas to use this Hydrogen instead. The Hydrogen will be created when the wind blows, and stored until needed.
Sounds good? Not when you see the big picture.
These wind farms are part of the national grid, which is itself 40% natural gas powered... and those natural gas stations are the best load followers (apart from the little bit of hydro) on the grid. Electrolysis is inefficient. It would be far better to convert the houses to electricity, not Hydrogen, and avoid the conversion step.
But it would be even better to convert the houses to natural gas and avoid both conversion steps... wait a minute. They were on natural gas before the project.
Yes, when you look at the big picture, the project doesn't reduce greenhouse gas at all. It increases it. Its only plus is that the Hydrogen can be stored.
But again, this is inefficient. Batteries are a much better way of storing energy. So even on the drawing board, this project is already a dismal failure.
But hydrogen gas was used in town gas without problems
Indeed it was. Water gas was an important component of traditional town gas. But at much lower pressure than that at which natural gas is now distributed.
And the embrittlement and leaks problems are related to the pressure (the partial pressure, strictly) of the hydrogen. The higher this pressure, the greater the problem.
Do you see the problem?
An anecdote
During World War Two my father, already a rather bald young man by the time I was born, worked on producing Tungsten for the Australian war effort. Before that he was a handsome young man with a full head of hair. (OK I'm biased.)
Before the war, Australia imported all of our radio valves (vacuum tubes for the Americans) from the good 'ole US of A. But during the war, the Americans being our friends and allies had to fight very hard to save us from the Japanese, so they needed all of their radio valves for their own radios and radars and sonars and so on. So they didn't have any for us. So we decided to make our own.
One of the vital materials for this was Tungsten.
Before the war, Australia imported all of our Tungsten from the good 'ole US of A. But during the war, the Americans being our friends and allies had to fight very hard to save us from the Japanese, so they needed all of their Tungsten for their own radio valves. So they didn't have any for us. So we decided to make our own.
One of the vital steps in this was refining the Tungsten in an electric furnace, a large bell jar filled with an inert gas. You feed a bar of unrefined Tungsten in at the top and it forms one electrode of an electric arc. The ingot of refined Tungsten at the bottom is the other electrode. Tungsten has a very high melting point, that's why it's used in radio valves. But in the middle of the arc, it melts, and as soon as it hits the ingot it solidifies again. And this process removes impurities.
Tungsten burns in air, so molten Tungsten will catch fire very readily indeed, so the inert gas is important. The gas of choice is Helium, which also stabilises the arc very nicely.
Before the war, Australia imported all of our Helium from the good 'ole US of A. But during the war, the Americans being our friends and allies had to fight very hard to save us from the Japanese, so they needed all of their Helium for various purposes. So they didn't have any for us.
You can't make Helium. The other source is the atmosphere but this Helium isn't pure enough, the good stuff comes comes from gas wells such as those in Louisiana. See above.
So we decided to use the next best thing. You guessed, Hydrogen. The seal at the bottom of the furnace is easy, the bell jar just sits in a ring of Mercury. The seal at the top is more of a problem, as it's where you're feeding in the raw Tungsten bar. And if even a little air gets in with the Tungsten... and the Hydrogen... and the electric arc...
Dad said that in hindsight he should have known that the furnace was about to blow up. It had blown up three times in the previous week. But on each of those occasions they had been able to put the furnace back together again afterwards. Dad never did anything by halves. When Alder blew the furnace up, they didn't even have enough left of the building to put it back together again, let alone the furnace.
The ring of Mercury probably saved his life. He was soaked in it. Naked or nearly so, he'd even lost his boots somehow (I don't know about his socks), and a bit abrased and bruised, and seared from the fire, and soaked in Mercury, but he and the project director (the only other one in the building at the time) both ran for their lives, almost got out of the building, but they got stuck in the doorway at which they both arrived at the same instant and then it blew. They were both soon back at work with a new furnace in a new building just across the road from the crater where the old one had been. It took more than a week to comb the Mercury out of their pores and what hair they still had, so they spent the nights in hospital and the days making Tungsten. War is like that.
But what with the Mercury and the fire, and maybe a bit from male pattern baldness as well, their hair never grew back.
Hydrogen is nasty stuff.
