5 ms·

"significantly" sells it short. Electric airliners need a couple orders of magnitude of improvement to even come close to viability.

Retric 6y ago
Jet engines are significantly less efficient than electric engines so it’s lithium ion has 1/20th the useful Specific Energy at takeoff, though that gets worse as the flight progresses and fuel is burned or batteries age. On the other hand for ultra long range flights electric jets can cruise as higher altitudes which makes up for some of that. Also having 1/3 the 15,000 km range of some aircraft is perfectly viable. IMO, Due to cost savings electric aircraft would likely become common at around 4x the current Specific Energy and fully take over at about 10-20x. PS: Energy density is fine for lithium ion, the issue is energy per weight (Specific Energy) not energy per volume (Energy Density).
- jakehop 6y ago
  An airplane will weigh less, the more jet fuel it uses. A battery powered airplane does not have an obvious way of losing weight in this manner, further limiting range. Talking about 5.000 km is hard: While it won't get you from London to New York without some post-crash landing swimming, the current largest electric plane can fly ~100 miles at around 114mph, with 9 passagers. I see that you take the laws of physics into account, but allow me to state this for the sake of the conversation: In order to replace jet fuel, we must match what we could call it's useful energy density (energy/kg * efficiency). While electric engines are probably more efficient, we're still up to 2 orders of magnitude away – that's requires a 50-100x improvement of energy density, while maintaining the needed high discharge characteristics, developing a sufficiently efficient electric jet engine and taking into account the increased weight. All at a price where people won't need to save up for years, in order to visit their families. While I hope to see a zero emission future in my lifetime (actually a negative-emissions might be needed for at time), I feel like putting batteries into airplanes is a bit too much "Silicon Valley Sophism" – shoving the same solution at each and every problem, rather than figuring out what the core of the problem is. I do love electric cars, but they are not for everyone('s budget). Perhaps the solution is synthetic fuels, combined with carbon capture and a cheap, clean and reliable energy source, such as nuclear power. I know this isn't exactly cheap or readily available either, but it seems like one would bypass a lot of the issues above, by focusing on the source of the problem: Non-neutral use of carbon fuels.
simonebrunozzi 6y ago
From what I've read, ONE order of magnitude higher density is all we need for commercially viable eletric airplanes. We don't need an additional 10X, as you are suggesting.
Robotbeat 6y ago
No they don’t. 400Wh/kg is sufficient when combined with structural efficiency and aerodynamic improvements. Over 1000 mile range should easily be feasible there in a new, clean sheet design incorporating best of everything and a 400Wh/kg battery.
andai 6y ago
Serious question, would nuclear powered planes be viable? As far as energy density goes it seems pretty hard to beat! https://xkcd.com/1162/ https://xkcd.com/1162/
- AI_WAIFU 6y ago
  They tried that. The problem is shielding the reactor and figuring out what to do in the event of a crash. https://en.wikipedia.org/wiki/Nuclear-powered_aircraft https://en.wikipedia.org/wiki/Nuclear-powered_aircraft Nuclear marine propulsion seems much more viable.
- wobbegongz 6y ago
  Yes, both USA and Soviet experimented with nuclear powered planes during the 60s. The problem was how to shield the pilots from radioactivity. https://en.wikipedia.org/wiki/Nuclear-powered_aircraft https://en.wikipedia.org/wiki/Nuclear-powered_aircraft They also experimented with nuclear powered drones. https://www.popularmechanics.com/military/research/a33565112/cia-nuclear-bird-drone-spy-communists-declassified/ https://www.popularmechanics.com/military/research/a33565112... And Russia now claims to have a nuclear engine that can make a cruise missile fly for days. https://en.wikipedia.org/wiki/9M730_Burevestnik https://en.wikipedia.org/wiki/9M730_Burevestnik
  - LargoLasskhyfv 6y ago
    What if there were a reactor type which would require no, or much less shielding because all it emits is mostly hard ultraviolet light? [0] https://en.wikipedia.org/wiki/Nuclear_lightbulb https://en.wikipedia.org/wiki/Nuclear_lightbulb
    - ben_w 6y ago
      I read that as using UV light to transfer energy to the working fluid, not that the actual nuclear reaction itself would be any different to any other nuclear reactor.
      - 6y ago

Retric 6y ago

Jet engines are significantly less efficient than electric engines so it’s lithium ion has 1/20th the useful Specific Energy at takeoff, though that gets worse as the flight progresses and fuel is burned or batteries age. On the other hand for ultra long range flights electric jets can cruise as higher altitudes which makes up for some of that. Also having 1/3 the 15,000 km range of some aircraft is perfectly viable. IMO, Due to cost savings electric aircraft would likely become common at around 4x the current Specific Energy and fully take over at about 10-20x. PS: Energy density is fine for lithium ion, the issue is energy per weight (Specific Energy) not energy per volume (Energy Density).

jakehop 6y ago
An airplane will weigh less, the more jet fuel it uses. A battery powered airplane does not have an obvious way of losing weight in this manner, further limiting range. Talking about 5.000 km is hard: While it won't get you from London to New York without some post-crash landing swimming, the current largest electric plane can fly ~100 miles at around 114mph, with 9 passagers. I see that you take the laws of physics into account, but allow me to state this for the sake of the conversation: In order to replace jet fuel, we must match what we could call it's useful energy density (energy/kg * efficiency). While electric engines are probably more efficient, we're still up to 2 orders of magnitude away – that's requires a 50-100x improvement of energy density, while maintaining the needed high discharge characteristics, developing a sufficiently efficient electric jet engine and taking into account the increased weight. All at a price where people won't need to save up for years, in order to visit their families. While I hope to see a zero emission future in my lifetime (actually a negative-emissions might be needed for at time), I feel like putting batteries into airplanes is a bit too much "Silicon Valley Sophism" – shoving the same solution at each and every problem, rather than figuring out what the core of the problem is. I do love electric cars, but they are not for everyone('s budget). Perhaps the solution is synthetic fuels, combined with carbon capture and a cheap, clean and reliable energy source, such as nuclear power. I know this isn't exactly cheap or readily available either, but it seems like one would bypass a lot of the issues above, by focusing on the source of the problem: Non-neutral use of carbon fuels.

simonebrunozzi 6y ago

From what I've read, ONE order of magnitude higher density is all we need for commercially viable eletric airplanes. We don't need an additional 10X, as you are suggesting.

Robotbeat 6y ago

No they don’t. 400Wh/kg is sufficient when combined with structural efficiency and aerodynamic improvements. Over 1000 mile range should easily be feasible there in a new, clean sheet design incorporating best of everything and a 400Wh/kg battery.

andai 6y ago

Serious question, would nuclear powered planes be viable? As far as energy density goes it seems pretty hard to beat! https://xkcd.com/1162/ https://xkcd.com/1162/

AI_WAIFU 6y ago
They tried that. The problem is shielding the reactor and figuring out what to do in the event of a crash. https://en.wikipedia.org/wiki/Nuclear-powered_aircraft https://en.wikipedia.org/wiki/Nuclear-powered_aircraft Nuclear marine propulsion seems much more viable.
wobbegongz 6y ago
Yes, both USA and Soviet experimented with nuclear powered planes during the 60s. The problem was how to shield the pilots from radioactivity. https://en.wikipedia.org/wiki/Nuclear-powered_aircraft https://en.wikipedia.org/wiki/Nuclear-powered_aircraft They also experimented with nuclear powered drones. https://www.popularmechanics.com/military/research/a33565112/cia-nuclear-bird-drone-spy-communists-declassified/ https://www.popularmechanics.com/military/research/a33565112... And Russia now claims to have a nuclear engine that can make a cruise missile fly for days. https://en.wikipedia.org/wiki/9M730_Burevestnik https://en.wikipedia.org/wiki/9M730_Burevestnik
- LargoLasskhyfv 6y ago
  What if there were a reactor type which would require no, or much less shielding because all it emits is mostly hard ultraviolet light? [0] https://en.wikipedia.org/wiki/Nuclear_lightbulb https://en.wikipedia.org/wiki/Nuclear_lightbulb
  - ben_w 6y ago
    I read that as using UV light to transfer energy to the working fluid, not that the actual nuclear reaction itself would be any different to any other nuclear reactor.
    - 6y ago