
The challenges of hydrogen for airliners, part 2: ecosystem - Xixi
https://leehamnews.com/2020/07/31/bjorns-corner-the-challenges-of-hydrogen-part-2-echosystem/
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woodandsteel
Two sorts of questions for those who support this idea

1) If is is so workable, then why don't we have hydrogen test planes flying
today? Are there any technological problems that remain to be solved?

2) How is hydrogen supposed to be better than synfuel kerosene produced with
renewable energy? And note than any argument must include the cost of
replacing every current airliner with an all new hydrogen one, as opposed to
keeping the present airliners.

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jeffreyrogers
I like hydrogen and support trying it in aviation (the Soviet Union actually
had an airliner that ran on liquid hydrogen, so this isn't really that new of
an idea), but I really don't see how hydrogen can compete on economics with
fossil fuels.

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jandrese
Thus far several companies have experimented with H2 aircraft and come to the
conclusion that it doesn't make sense with current technology.

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ncmncm
New insulation technology changes the balance. Practical aerogel production
means that heavy, shape-constrained high-pressure tankage is no longer needed,
so that tanks may now be light and have the most convenient shape.

Furthermore, recent advances in catalysts for hydrolysis, some directly from
sun exposure with no detour through electric form, make production of hydrogen
from water and light practical.

New airframes with lifting-body designs, already better than those used now,
have more room for tankage as a side benefit.

The practicality of any idea can change very, very rapidly, as details of
solutions to engineering problems change. Recently solar and wind power were
impractical. Now they are cheapest, and coal-fired power is impractical.

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woodandsteel
Is anybody building a plane that makes use of these new technologies?

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ncmncm
No. At least not that they are telling anyone about. But there is plenty of
evidence people equipped to do something are thinking about it.

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bfuclusion
Bring back the Zeppelins:) There's lots of missions they can do besides
passenger carrying, and they do it better than aircraft.

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jandrese
I'm not seeing much advantage of running off of H2 instead of a biofuel like
ethanol, especially if we get switchgrass or other less energy intensive forms
of biofuel production off of the ground.

H2 has so many storage and handling challenges that are going to be compounded
when weight is an issue that its hard to see its future in the airline
industry.

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p_l
The problem with biofuels in aviation is that the most common available forms
have... problems with storage and weight of the system. Because ethanol
evaporates too fast, which is the same reason why aviation still uses leaded
gasoline, and why ethanol additives are very limited.

Remember, aviation fuels need to work way above 10km above sea level.

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jeffreyrogers
I'd assume ethanol would be converted to something like kerosene, since that's
what jet engines burn anyways. But without regulation I don't see the
incentive to use biofuels. They're significantly more expensive and don't
offer any performance benefits. Hydrogen has the same problems btw.

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woodandsteel
One gigantic advantage for synfuel kerosene that is carbon-neutral because it
is produced with renewable energy, is you can continue to use the present
airliner fleet. With hydrogen you have to spend many trillions of dollars
replacing it.

Furthermore, replacing all the planes would take many decades, while synfuel
kerosene might go into production much sooner.

Do the hydrogen airliner boosters take all that into account?

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avmich
> Do the hydrogen airliner boosters take all that into account?

Sure, and other things too, like combustion benefits and hazards. But
regarding your money worries - they don't need to happen overnight, just like
electric cars don't replace gasoline ones suddenly.

Hydrogen fundamentally more potent fuel than kerosene - both by energy density
and heat characteristics. Like with other commercial technologies, to be
accepted it has to change traditions somewhat, which isn't easy. Safety is
another important matter - it remains to be seen if hydrogen can be safely
brought onboard to regular commercial liners, though advancements demonstrated
by Toyota Mirai remind that progress doesn't stand still.

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woodandsteel
It may well be that hydrogen is the fuel of the future for airlines. The
problem is that with the rate global climate change is happening, we can't
wait decades for a solution. We need something as soon as possible, and as far
as I can tell, synfuel kerosene could replace fossil fuel kerosene decades
sooner than hydrogen could. Do the hydrogen boosters address this concern?

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jaywalk
I realize that this very different, but hydrogen is very negatively associated
with aviation.

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jandrese
Don't worry, nothing could ever go wrong with pressure vessels filled with
heavily compressed explosive gas, especially in an accident.

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ncmncm
Thus, don't compress it.

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jandrese
Bring back Zeppelins?

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ncmncm
Current discussion focuses on liquifaction, which enables transport without
high pressure.

