Interesting idea on creating a competitive fuel cell aircraft by 2020…
http://spectrum.ieee.org/aerospace/aviation/how-i-designed-a-practical-electric-plane-for-nasa
He says “Another hurdle is that hydrogen has not yet caught on as a fuel for automobiles, much less for airplanes”.
Hydrogen will never catch on: it’s very difficult and dangerous to store (the small molecules leak through things and embrittles pressure vessels), it’s inefficient to make, if you use a less dangerous storage method than a high pressure cylinder that’s getting gradually more brittle you end up requiring quite a lot of energy to get the hydrogen into and out of the storage medium. If you don’t like avgas in planes because of its flammability, well, now you have two problems – a flammable gas at high pressure that can rupture during an accident.
A fuel cell aircraft or car is a non-starter until you can at least practically use natural gas as the fuel rather than hydrogen. Hydrogen is orders of magnitude more difficult and dangerous to handle than lithium ion batteries.The key to electric aircraft (and cars with decent range for that matter), is battery technology….once you can store the equivalent (useable) amount of energy in the same or less weight and volume as a tank of gasoline then job sorted…. If you believe Moore’s Law that should be sometime in the next decade or so…
alioth wrote:
A fuel cell aircraft or car is a non-starter until you can at least practically use natural gas as the fuel rather than hydrogen.
Better even some easily storable and transportable liquid. There is some progress in direct methanol and ethanol fuel cells but the efficiency is not good enough yet https://en.wikipedia.org/wiki/Direct-ethanol_fuel_cell and https://en.wikipedia.org/wiki/Methanol_economy . Both alcohols can be made in a variety of ways, methanol can be completely synthesised using CO2 from the air. But hydrogen as fuel for small aircraft or cars? Never.
I believe Elon Musk once said “Hydrogen is the future, and always will be!”
That said there are a few hydrogen filling station local to me for the Mirai car that is being trialled here.
I think it has more applicability in aircraft than cars due to the available unused package space for low pressure storage in wings and fuselage, but still a lot of challenges for a cryogenic fuel that leaks through everything.
Moore’s law was something like a doubling every 18 months; I think battery technology is more like 5-6% p.a. on cost down and energy density up, but still a useful trend.
Mark_1 wrote:
I believe Elon Musk once said “Hydrogen is the future, and always will be!”
So why aren’t even his own Falcon rockets powered with hydrogen? 
Because it isn’t the present, perhaps 
I share the scepsis about hydrogen: some experiments were done here with a hydrogen-powered bus several years ago, but nothing came of it. And I don’t think the relevant technology has made so very much progress over 20 years or so.
However, searching for a reference for that old experiment, I learned that 5 hybrid-powered buses are now running on hydrogen – interestingly, they are supplied from some chemical plant in the Antwerp port (the world’s second biggest concentration of petro-chemical industry, after Houston) where H2 is a residual from some production process so it is a win-win formula. Still, a good deal of European subsidy is involved.
(Only in local language:)
http://www.hln.be/hln/nl/2764/milieu/article/detail/1885209/2014/05/13/Eerste-hybride-waterstofbus-van-De-Lijn-is-een-feit.dhtml
I believe Elon Musk once said “Hydrogen is the future, and always will be!”
The key bit is “always will be”
In other words, it will never be in the present.
It’s closely tied to nuclear fusion. That has also had a fantastic future – for the last 50 years. If they ever get it to work (which I am sure they will one day) we will get very cheap electricity and then very cheap oxygen and hydrogen, by splitting seawater. The hydrogen storage problem won’t go away though…
BTW electric cars have a limited future IMHO because their current USP is electricity which is extremely cheap because the powers to be have not yet got around to taxing it. They are prob100 not going to let go of hydrocarbon taxes so when that starts to fall (IF electric cars ever become significant – there have been many short lived fashions) they will introduce a replacement for the income, which will probably have to be road (mileage based) pricing, because jacking up electricity bills to fully compensate would impoverish everybody. A while ago I went to a seminar by some “big knob” in the electric car business and he said this is completely expected to happen, so the present very low DOC advantage will disappear.
Jan_Olieslagers wrote:
However, searching for a reference for that old experiment, I learned that 5 hybrid-powered buses are now running on hydrogen – interestingly, they are supplied from some chemical plant in the Antwerp port (the world’s second biggest concentration of petro-chemical industry, after Houston) where H2 is a residual from some production process so it is a win-win formula. Still, a good deal of European subsidy is involved.
City buses are probably the most convenient platform for testing alternative means of propulsion: they don’t need to be fast, have a very limited operating range, and can easily accommodate bulky and heavy additional equipment. Probably the most exotic system among those already tried was a gyrobus with flywheel-based energy storage. I’m told there is one in a museum in Antwerp.
