4 ms·

Long-haul flights are the one possible exception, but they're not the saving grace the fossil fuel companies are trying to manufacture. Tanks of hydrogen at the

by gary_0 3y ago

Long-haul flights are the one possible exception, but they're not the saving grace the fossil fuel companies are trying to manufacture. Tanks of hydrogen at the airport are not a "hydrogen economy". And since it's looking like air travel will be one of the last things to decarbonize, there's no guarantee hydrogen will be relevant. Long-distance flights don't account for a large portion of global CO2 emissions[0] which leaves room for various options. Short-range aircraft will probably switch to batteries in the coming decades, because the prototypes are already flying[1] and battery and electric motor tech is ever-increasingly ubiquitous and mature. [0] https://en.wikipedia.org/wiki/Greenhouse_gas_emissions#Aviation https://en.wikipedia.org/wiki/Greenhouse_gas_emissions#Aviat... [1] https://www.cbc.ca/news/canada/british-columbia/vancouver-electric-seaplane-test-flights-1.5884479 https://www.cbc.ca/news/canada/british-columbia/vancouver-el...

Manuel_D 3y ago
It's not just long haul flights, it's really anything longer than a hundred miles or so. Battery powered aircraft are also very small and light with little passenger or cargo capacity. Then there's the issue of charging. Planes can't just sit idle for hours at th gate as they charge. Faster charging reduces the lifespans of the batteries, and a plane needing a new set of batteries after a few hundred flights due to aggressive wear from fast charging is unacceptable. It's not just long haul flights out of reach of battery powered aircraft. Even a regional flight like Seattle to San Francisco cannot be feasibly done with batteries. This is fundamentally due to the energy density of lithium ion batteries, no amount of engineering can change the chemical limitations at hand: https://en.m.wikipedia.org/wiki/Energy_density#/media/File%3AEnergy_density.svg https://en.m.wikipedia.org/wiki/Energy_density#/media/File%3...
- _aavaa_ 3y ago
  > Faster charging reduces the lifespans of the batteries As far as I understand, the problem is not just the speed, but the thermal management. IIRC the impact on battery life is not as bad if cooled properly. > and a plane needing a new set of batteries after a few hundred flights due to aggressive wear from fast charging is unacceptable. That's an economics question. How much does it cost to get that battery replaced and charged over its lifetime versus the alternative. > This is fundamentally due to the energy density of lithium ion batteries, no amount of engineering can change the chemical limitations at hand That's the beauty of battery technology, you can substitute. Cobalt a problem? Fine we can make batteries with out it. Lead-acid not suitable, fine here's lithium ion. Lithium ion not good enough, find we'll find a better battery. Hydrogen however is just that: hydrogen. Notice how low it is on the energy per volume scale. You can't substitute it out for anything. The volume requirement is what's going to kill you with hydrogen.
  - Manuel_D 3y ago
    > Lithium ion not good enough, find we'll find a better battery. Well, then get back to us when you find that battery. Unfortunately, simply finding a new battery chemistry that has an order of magnitude better energy density is easier said than done. > Hydrogen however is just that: hydrogen. Notice how low it is on the energy per volume scale. You're looking at uncompressed hydrogen. Hydrogen at 700 bar has several times better energy density than lithium ion batteries, and over 1000x as much energy by mass. And lower mass means you need less fuel since the craft is lighter.
Gibbon1 3y ago
A point if and I seriously mean if in the I'm exceptionally dubious about hydrogen powered aircraft. If aircraft were hydrogen powered you'd generate the hydrogen on site at the airport. Will point out takes a decade now to produce a blue print aircraft. So if we started designing one now it would be flying when 2033? China rolled out a high speed rail network in ten years. You could do that in the US and other places. Notable point. The complaints I hear about high speed rail in Europe is tickets cost more than airplane tickets and the trains are always full. The explanation is the ergonomics and logistics of passenger aircraft sucks.
- _hypx 3y ago
  You'd likely send via pipelines or tanker trucks instead.
  - c_o_n_v_e_x 3y ago
    Hydrogen doesn't make sense to transport. You contend with cryogenics / boil-off for tanker trucks or ships. Pipelines you're dealing with poor volumetric energy levels (you use comparatively more units of energy to move one unit of h2).
    - _hypx 3y ago
      Boiloff is not that big of a deal if you are using the fuel right away. It is the same story as with LNG.
      - c_o_n_v_e_x 3y ago
        I replied to your comment that was talking about transportation... i.e. not using it right away. H2 has a daily boil off 5 times greater than LNG. https://www.sciencedirect.com/science/article/pii/S2772656822000276 https://www.sciencedirect.com/science/article/pii/S277265682... Not only that, liquid H2 has worse energy density than LNG. So again, you're spending more units of energy to comparatively more less units of energy.
WorldMaker 3y ago
If flights are carrying that much hydrogen around with them they should also just use them for "free" lift. I don't think hydrogen fuel tanks save the airplane, I think they return us to economic models where the blimp/airship make more sense.
- loeg 3y ago
  Liquid hydrogen is significantly denser than air.
  - WorldMaker 3y ago
    Right, which is why it "weighs" more and starts to make sense for a flying vehicle to store more of it as gas (less weight, more ballast) and the more you store as gas the closer you get to reinventing airships/blimps/zeppelins.

by gary_0 3y ago

Manuel_D 3y ago

It's not just long haul flights, it's really anything longer than a hundred miles or so. Battery powered aircraft are also very small and light with little passenger or cargo capacity. Then there's the issue of charging. Planes can't just sit idle for hours at th gate as they charge. Faster charging reduces the lifespans of the batteries, and a plane needing a new set of batteries after a few hundred flights due to aggressive wear from fast charging is unacceptable. It's not just long haul flights out of reach of battery powered aircraft. Even a regional flight like Seattle to San Francisco cannot be feasibly done with batteries. This is fundamentally due to the energy density of lithium ion batteries, no amount of engineering can change the chemical limitations at hand: https://en.m.wikipedia.org/wiki/Energy_density#/media/File%3AEnergy_density.svg https://en.m.wikipedia.org/wiki/Energy_density#/media/File%3...

_aavaa_ 3y ago
> Faster charging reduces the lifespans of the batteries As far as I understand, the problem is not just the speed, but the thermal management. IIRC the impact on battery life is not as bad if cooled properly. > and a plane needing a new set of batteries after a few hundred flights due to aggressive wear from fast charging is unacceptable. That's an economics question. How much does it cost to get that battery replaced and charged over its lifetime versus the alternative. > This is fundamentally due to the energy density of lithium ion batteries, no amount of engineering can change the chemical limitations at hand That's the beauty of battery technology, you can substitute. Cobalt a problem? Fine we can make batteries with out it. Lead-acid not suitable, fine here's lithium ion. Lithium ion not good enough, find we'll find a better battery. Hydrogen however is just that: hydrogen. Notice how low it is on the energy per volume scale. You can't substitute it out for anything. The volume requirement is what's going to kill you with hydrogen.
- Manuel_D 3y ago
  > Lithium ion not good enough, find we'll find a better battery. Well, then get back to us when you find that battery. Unfortunately, simply finding a new battery chemistry that has an order of magnitude better energy density is easier said than done. > Hydrogen however is just that: hydrogen. Notice how low it is on the energy per volume scale. You're looking at uncompressed hydrogen. Hydrogen at 700 bar has several times better energy density than lithium ion batteries, and over 1000x as much energy by mass. And lower mass means you need less fuel since the craft is lighter.

Gibbon1 3y ago

A point if and I seriously mean if in the I'm exceptionally dubious about hydrogen powered aircraft. If aircraft were hydrogen powered you'd generate the hydrogen on site at the airport. Will point out takes a decade now to produce a blue print aircraft. So if we started designing one now it would be flying when 2033? China rolled out a high speed rail network in ten years. You could do that in the US and other places. Notable point. The complaints I hear about high speed rail in Europe is tickets cost more than airplane tickets and the trains are always full. The explanation is the ergonomics and logistics of passenger aircraft sucks.

_hypx 3y ago
You'd likely send via pipelines or tanker trucks instead.
- c_o_n_v_e_x 3y ago
  Hydrogen doesn't make sense to transport. You contend with cryogenics / boil-off for tanker trucks or ships. Pipelines you're dealing with poor volumetric energy levels (you use comparatively more units of energy to move one unit of h2).
  - _hypx 3y ago
    Boiloff is not that big of a deal if you are using the fuel right away. It is the same story as with LNG.
    - c_o_n_v_e_x 3y ago
      I replied to your comment that was talking about transportation... i.e. not using it right away. H2 has a daily boil off 5 times greater than LNG. https://www.sciencedirect.com/science/article/pii/S2772656822000276 https://www.sciencedirect.com/science/article/pii/S277265682... Not only that, liquid H2 has worse energy density than LNG. So again, you're spending more units of energy to comparatively more less units of energy.

WorldMaker 3y ago

If flights are carrying that much hydrogen around with them they should also just use them for "free" lift. I don't think hydrogen fuel tanks save the airplane, I think they return us to economic models where the blimp/airship make more sense.

loeg 3y ago
Liquid hydrogen is significantly denser than air.
- WorldMaker 3y ago
  Right, which is why it "weighs" more and starts to make sense for a flying vehicle to store more of it as gas (less weight, more ballast) and the more you store as gas the closer you get to reinventing airships/blimps/zeppelins.