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[Crissa]

Exactly:  Hydrogen isn't unduly dangerous, not compared to other energy sources.  The big problem is that it can't be used without infrastructure.

I didn't understand why when they built the filling stations they didn't place them along a truck route they replaced trucks with.  Because that's what Tesla is doing with its Semi:  It builds the stations, then runs the trucks between them.

Cars really are the last place for hydrogen.  They go random places instead of set routes, and so need far more infrastructure before they're viable.

A new fuel makes the most sense for vehicles that ply a set route.  That makes the infrastructure installation cheaper.  Once you have a bunch of set routes, eventually you have the map covered.  Bonus for something like hydrogen that is relatively bulky (but light) which means it fits beat in things like boats, trucks, and trains... things that don't care about bulk as much as something like cars (or worse, motorcycles).

-Crissa

[princec]

Hydrogen for planes is a good idea, I think. And probably trains.

Cas

[Crissa]

Planes don't have extra volume.  Extra volume is extra drag.

-Crissa

[Fran K]

I think the real reason that hydrogen is so unpopular is because it creates far more problems than it solves. It's super-dangerous and incredibly difficult to use safely. It's not at all efficient to produce by the time it gets into a fuel tank. It's very hard to transport in any quantity. A remarkable amount of it simply escapes without being burned, and leaving it in a fuel tank for a long time eventually leaves you with ... no hydrogen. The engine tech required is even more complex than the most complex petrol engines and doesn't lend itself to small applications at all.

Then you compare it to electricity from a battery and an electric motor and you'd be thinking, why would anyone ever think it was a better idea? Which is why we're in this forum.

Cas

I am in agreement lots for the first half or so.
I would hope the use in transportation would be with fuel cells and electric motors so hydrogen power is still electric if in a motorcycle.
The compressed aspect seems to have made the chemical storage in Metal hydrides hardly considered.
I would think hydrogen has strategic implications think space force.

As for the solid state batteries or the cells in them it seems there is volume shifting inside the cell.  Perhaps not a solid as one might think of as first?

[Richard230]

One problem that I have with H2 in vehicles, much less airplanes, is the weight of the fuel tank. I bet a tank that can handle 700 bars of pressure is not very light and takes up a considerable volume which is not something that can be placed out of the way under the vehicle like a battery pack can. And who wants a tank of highly compressed H2 between their legs while riding a motorcycle?   

[princec]

I believe that the majority of the tank's structure for H2 would be carbon so very light. And you would probably not want to be terribly close to it in the event of a crash, no.

Cas

[Crissa]

They're very light.

And have to take extreme damage to burst.

-Crissa

[princec]

Dunno about burst, but they only need a rather tiny rupture to release an awful lot of hydrogen at 30 bar or whatever daft pressure it's at.

Cas

[Richard230]

Dunno about burst, but they only need a rather tiny rupture to release an awful lot of hydrogen at 30 bar or whatever daft pressure it's at.

Cas

You get your choice of 350 bar or 700 bar at the Sky Londa H2 station.   

[princec]

Hmm a chap I worked with had the end of his finger sliced clean off by a leaking 150bar line with a hairline crack in it.
(You won't believe this but many years later he then sliced the end of his thumb off with a circular saw reaching behind it... I said to him I thought you'd be more careful after the first one )

Cas

[gregj]

Hydrogen could be stored quite safely in a porous ultralightweight foam matrix to help reduce run away ( cascade) explosion on pressure release. It could also be stored between the outer and inner shell of the cylindrical body of the plane
Hydrogen is not as dangerous as made out. For a start, 2(H2)+O2= 2(H20) ie 3volumes becomes 2 volumes, so the untemp risen reaction is IMPLOSIVE.
If you are thinking Hindenberg, the massive fireball was caused as much by the nitrocellulose doped fabric as the ruptured hydrogen.
A porous metal hydride store could also help keep it stable or a liquid source compound.

[caza]

There have been lots of improvements in hydrogen safety. The fact is any dense energy source has dangers, including gasoline, and our batteries.

Hyundai uses carbon-fiber reinforced plastic that's actually designed to rip apart on a huge impact in order to disperse the hydrogen rather than compress it further and cause an explosion.

Again, most of the complaints about hydrogen are not the things stopping it from gaining mass adoption. Gasoline is dangerous, relatively expensive, but entirely convenient. The safety and efficiency issues of hydrogen are really non-issues when we compare them to gas. And even compared to BEV's, once a hydrogen infrastructure is set up, we need far less precious minerals to be mined since the battery doesn't need to be nearly as big per car. This is a huge advantage when we hit the volume of gas cars.

Hydrogen's biggest problem is simply a logistical and funding problem. But the impact of that problem cannot be overstated.

[Eicas]

I think that hydrogen will make in roads into trucking, trains, and large transport aircraft by the end of this decade. 

Batteries will continue to improve and become more and more popular for cars, bikes, etc.  Politics will push it forward along with needed infrastructure.

With hydrogen you probably have to go with liquid hydrogen to make it viable and that requires cryogenic bottles for storage and that creates design and distribution problems.

On large aircraft, today's batteries are just too heavy to be considered, the higher power density of hydrogen makes it doable but storage is a problem since it can not just be pumped into the wings as with kerosene.  Todays "jet" engines can be run on hydrogen with relatively small design changes and it appears that they will be more efficient than when burning kerosene. Airbus is doing a lot of work in this area now.  Boeing seems to be concentrating on biofuels.