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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 pass

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.

_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.