[isthispermanent]

The fuel cell tech isn’t the problem, it’s that there is no hydrogen gas infrastructure. And there’s certainly no robust H supply that doesn’t include fossil fuel to create the H gas.

Hydrogen fuel cells are just this constant pie in the sky thing. Stop making them and go solve the H infra problem, that’s the barrier.

[kurthr]

Hydrogen is a terrible battery. Best case conversion to H2 is ~80%, while best case fuel cell efficiency is ~50%. That's 40% round trip while most batteries can do 90%.

That ignores losses due to leakage, but those are only a couple of percent. Also, ignore the hazards, but the cost of building safe low leakage infrastructure might exceed the cost of batteries and solar/wind to produce power. You're probably better off making H2 dynamically where you need it and just sending electrons or storing them locally in safe batteries.

[sofixa]

> Hydrogen is a terrible battery. Best case conversion to H2 is ~80%, while best case fuel cell efficiency is ~50%. That's 40% round trip while most batteries can do 90%.

And batteries are terrible at storing energy if you care at all about weight... which airplanes very much do. Every extra gram impacts range, speed, usable capacity, etc. etc.

[kurthr]

Well, I was talking about infrastructure for transporting Hydrogen to the airfield. But wait, there is some low weight safe storage mechanism for high density hydrogen storage in a commercial passenger aircraft?

Oh, not cryogenic that's not just heavy, it's dangerous and bulky which is a real problem for realistic volumes. Not ultra high pressure tanks, since those are relatively bulky, dangerous, and heavy. Certainly not metal hydrides! To achieve the energy density of diesel you need about 4000:1 better than STP (300K 15psi). So at 100K and carbon fiber tanks at 10,000psi you can get about half the density (easy to calculate since H2 is close to ideal). That's dangerous heavy, expensive, and bulky!

Problem is the size and weight of the fuel cells and the cooling/heating you have to do to keep them efficient are comparable to the weight and size of the hydrogen storage. You can't really ramp them up quickly and the difference in peak power vs cruising power is easily 5x and usually you want margin. So you need a lot of fuel cells, but usually also for redundancy batteries for several minutes, in case there's a failure during take off. So you're gonna have batteries anyway. Most of the demos have been with just batteries or only running a single engine off of hydrogen. It's pretty funny.

p.s. I have friends in that very fuel cell plane company.

[lgbr]

> Hydrogen is a terrible battery. Best case conversion to H2 is ~80%, while best case fuel cell efficiency is ~50%. That's 40% round trip while most batteries can do 90%.

While there's no arguing with the physics here, don't forget the economics either. The price of electricity in Denmark on a cloudy, windless early evening can easily be 10 or more times the price in Newfoundland. Then start factoring in that a plane carrying hydrogen is significantly lighter than a plane carrying batteries.

While you might be using 10x as much electricity at the point of generation, you're paying a lot less for it, and you're using it more efficiently.

[7952]

Poor conversion factors may still be viable if the electricity can be bought cheaply enough and the hydrogen sold at a high enough price.

[dmitrygr]

People say stuff like this a lot, my guess is that you don’t fly airplanes. The fact that the airplane gets lighter as it burns fuel is kind of important and is used to simplify airplane design a lot (check out the difference between MTOW and MLW of a 777) . Batteries don’t get lighter.

[kurthr]

To be polite, my guess is you've never tried storing dense hydrogen or running high power fuel cells. The solutions are large, heavy, expensive, and not very safe in enclosed areas. The solutions under consideration involve batteries for backup.

[dmitrygr]

I never said H2 is the solution (I do not believe so). I just said that batteries are NOT.

[kurthr]

Who (other than ZeroAvia) is talking about batteries for flight?

For more information, please reread.

   "the cost of building safe low leakage infrastructure might exceed the cost of 
   batteries and solar/wind to produce power. You're probably better off making H2 
   dynamically where you need it and just sending electrons or storing them locally 
   in safe batteries."

[jauntywundrkind]

Water electrolysis will produce hydrogen. Of course then you also need to compress it. And the fuel cell itself is yet another even more woeful knefficiency. But maybe solar continues to get cheaper to the point where we don't care about the inefficiency. Not likely, not what I believe, but maybe it could work out. For a sea plane especially, it feels like you have what you need in abundance for this infrastructure: water, and open space for solar.

MIT also talked up a solar thermochemical hydrogen production system ~9 months ago, which claims a 40% efficiency. One still needs to compress that down but still a huge leap if that promise can be delivered on. https://news.mit.edu/2023/mit-design-harness-suns-heat-produ...

There is something really compelling about hydrogen, as the most energy dense fuel we can use, that is in mass abundance, that doesn't pollute. Conceptually it's very very cool. I'd love like heck to see X-33 or Venture Star designs dusted off with modern compositeaterial sciences, see something like Skylon make it to the sky. But it does seem incredibly cumbersome & hard & weighty to make infrastructure & fuel storage for. It doesn't seem likely. It seems like an illogical investment given the downsides difficulties & inefficiencies. But I still allow: maybe.

[lgbr]

> And there’s certainly no robust H supply that doesn’t include fossil fuel to create the H gas

The government of Chile published a pretty clear national strategy to address this very issue [1]. And with Chile being on the Pacific Ocean, and these seaplanes most likely being used in islands in the Pacific, it's not hard to imagine a relatively simple solution to the infrastructure issue.

1: https://energia.gob.cl/sites/default/files/national_green_hy...

[bryanlarsen]

Green hydrogen infrastructure is not the barrier, at least not in the sense that most people think it. Hydrogen is very difficult/expensive to transport and store. So much so that local production is likely to be solution. IOW, the airport will require electricity and water infrastructure, and will create hydrogen at the airport. So the infrastructure that is required is having small-scale electrolysis equipment on the market.

[oneplane]

If the article is anything to go by, the clue isn't as much the fuel cell itself, but the idea of having an engine that can be powered by any source of electricity. So instead of swapping out the engine for a different type, you only swap out the power storage method. If they have lithium and fuel cells now, but something else comes along later, it means a very localised change is all it takes to try it out and if feasible, put it in production.

For ICE propulsion you'd have to change a ton of things if you were to switch fuel types as the engine, the pumps, the tank, the hoses, sensors are all over the place and all have to change when you need to support a different fuel. (i.e. when switching from say, a liquid fuel to a gas or something like that) If I'm not mistaken, that's also why all the changes (not even innovation) have such small impact so far, because all they really can do is make sure that 'new' fuels behave the same way as old fuels, and new engines behave the same on the fame fuel as old engines. It's a deadlock.

[akamaka]

There is hydrogen airport infrastructure under development, with this project aiming for commercial flights by 2035: https://aviationsourcenews.com/airport/airbus-leads-uk-hydro...

But it takes a decade to design and test a new airliner, so of course we should expect to hear mostly about the startups developing planes at this point.

[Qwertious]

There's no point building the infrastructure if there are no planes to use it, though. When cars were first invented, you bought the fuel from the local chemist, and petrol stations only came years afterwards.

[tuna74]

If you have electricity and water you can make H2 gas. Storing it is quite costly, so you probably want to make it on demand (like the Hybrit project will do).