As for "applications" - basically the only application for hydrogen that has big engineering advantages with current tech is in longrange aviation, where it grants a bit more than double the range, and we're going to have to wait for China to launch a liquid hydrogen combustion scramjet bomber for anyone in the industry to actually care about that capacity enough to overcome the logistical hurdles of airports supplying a deep cryogenic gas and the innate conservatism of aerospace design. I believe we'll have standardized regional lithium ion aviation long before we build antipodal liquid hydrogen planes.
https://www.airbus.com/en/newsroom/stories/2024-09-developin...
TL;DR Airbus is confident that they will have solved the technology development and logistical hurdles and will have commercially available hydrogen airplanes with ~100 passengers before 2035. There are serious R&D programs working on this across Europe. Cryogenic engineering is not some voodoo that nobody understands.
Anybody that presents terms like "green hydrogen", "blue hydrogen", emphasizing the renewable nature of hydrogen, is BSing you. The case will never close on these merits.
The case can't even close on a prototype basis unless we're using liquid hydrogen. Gaseous pressure vessels are orders of magnitude too heavy.
What liquid hydrogen combustion does in the short term is gives you a fuel that's difficult to produce & distribute but more than twice as effective gravimetrically as fossil fuels, so long as you design a plane around the fuel tank rather than the other way around. Twice the range.
Any other merit of hydrogen combustion, you can beat with biofuels that are (comparatively) cheap to produce and far easier to distribute. Or just use fossil fuels directly.
We don't know if there will ever be hydrogen fuel cells (giving you ten, twenty, thirty percent more percent range over combustion) that are power-dense enough to function; A few companies claim they've made advances but haven't brought anything to market.
As solar gets cheaper, splitting water molecules gets cheaper. I don't see any strong reason why the current energy race won't continue for the foreseeable short-term future, so there's no other "next energy race" coming soon.
at the time rumor had it that the chinese alkaline systems were producing green hydrogen for $2 - 3/kg
the inflation reduction act put some monster subsidies in place that added up to something like $3 or $4 per kg, so effectively they were trying to force the economies of scale by moving the price drops forward several iterations.
of course the new administration is already ripping apart that legislation, so its doubtful much of that will pan out now (if you ever thought it would).
in the meantime, the price of a kwh of wind/solar has continued to decline rapidly, so the original $4-5 estimates can be reasonably eyeballed down to $3 - $4 now. still not enough, but in a decade it might be.
of course as with all of climate change economic math, so long as pollution is free its difficult to cost compete with.
Hydrogen is and will remain a relatively niche player given its use case (industrial) and complexity of managing. Wish it were different.
the IRA would have been a massive infusion, but it passed in '22, after the rate hikes (its how/why it got its dumb name). Even still most of its effects were convoluted tax credits that are difficult to model investment risk on right now (putting it nicely).
I know mass is not the same measurement as weight, but we still mostly use weight to measure mass, don't we?
Obviously this has already been solved for helium, but is it just measuring volume and converting? Or pressure level in a known volume? Or I guess if you pressurize it enough it'll be more dense than air.
What a fun problem!
FYI from searching the internet and asking chatgpt, I came up with these rules of thumb regarding BTU equivalency:
10 gallons of California RFG gasoline is equivalent to
10 kg of hydrogen
12 CCF natural gas
9 gallons of low sulfur diesel
330 kWh of electricity