Finding a way to store liquid hydrogen in 4x the volume (plus any required cooling/insulation and safety systems) might be a challenge for long-haul flights.
Yes there are some ways to produce hydrogen from electricity with electrolysis but at the moment 90% of hydrogen use natural gas or other hydrocarbons and release enormous amount of CO2.
Hydrogen production can be clean though.
https://www.cleanenergywire.org/news/hamburg-and-fukushima-c...
Don't misunderstand me, I want a low-carbon aviation, I'm all for it. But even if you cut the emissions by a factor 2 of each newer aircrafts, what's the point? The numbers of flights is expected to double in less than 20 years. Global emissions won't reduce at all.
https://www.iata.org/pressroom/pr/Pages/2018-10-24-02.aspx
IMHO, we need more regulations (e.g. ban domestics flights if high-speed trains are a viable alternative) rather than technological solutions.
Yes, it's silly to ignore realities like "how was the electricity powering this car produced?" OTOH, since we're talking about potential future solutions to a hard problem (hard relative to cars, for now)... you kind of need to dismiss current issues if they're solvable to in theory.
Price of electrolysis hydrogen now, when we're not using that much of it is not necessarily indicative of potential prices at scale.
To me, I think we need to focus regulation that gets high potential technologies (eg electricity production and electric transport, atm) past the point on their learning curves where ordinary price economics and/or bans on carbontech can take over.
The problem with marginal mitigation like discouraging flights or large ICE engines is that gains are one-off, and not en route to bigger solutions.
I agree that commercial flight is a big problem. I'm just skeptical that carbon austerity can amount to more than a rounding error in the long term.
1lb of jet fuel has roughly 5kwh of energy. Of course you are going to get less than half of that out as useful work. But an airliner can carry 300000lb of fuel. So as a first order approximation you are going to need 10000+ Tesla battery packs to do the same job.