5 ms·

500-600 Wh/kg is the target for replacing average flight durations. Fuel is one of the highest costs for an airline, so eliminating the majority of that will m

by gibolt 3y ago

500-600 Wh/kg is the target for replacing average flight durations. Fuel is one of the highest costs for an airline, so eliminating the majority of that will make the demand for any viable options go bananas, even with a much higher upfront cost. Being seen as 'green' is a big bonus for the airline.

baq 3y ago
If the tech takes off (pun intended) every major airport will need a SMR. Which is maybe good? But politically impractical today.
- mlsu 3y ago
  With the energy efficiency attainable by traveling in the upper atmosphere, this might be the greenest possible long range transportation. God such a tantalizing solar punk dream. I would love just to hear the inside of an electric commercial airliner at altitude.
  - VBprogrammer 3y ago
    Presumably they would use something like an electrically propelled ducted fan (basically the first stage of a high bypass engine). The noise I imagine would be reasonably similar.
    - nerpderp82 3y ago
      I think a hybrid approach with a high bypass turbo fan powered by an electric motor. The fan could then switch over to a https://newatlas.com/automotive/inside-out-wankel/ https://newatlas.com/automotive/inside-out-wankel/ when at cruising altitude. Using biofuels, or carbon air capture, we get long range and a closed carbon cycle.
  - _puk 3y ago
    I doubt it would be classical music and whale song playing over a beautifully calm scene.. More like kids watching movies without headphones, over loud conversations and screaming babies if other public transport is anything to go by. But we can dream!
    - SapporoChris 3y ago
      Experiences vary. I was on a Tokyo subway train (Chūō-Sōbu Line(Local)). For a couple of minutes after boarding it was so quiet that it was eerie. When I started hearing quiet noises I relaxed. Anyway, mass transit does not have to be noisy. It varies by custom and culture.
      - ryalistik 3y ago
        [dead]
- oblio 3y ago
  What's SMR?
  - Flockster 3y ago
    I would assume a Small Modular Reactor.
- regularfry 3y ago
  Less of the "S". With current flight patterns you need multiple gigawatts. Calculations based on 737s leaving Gatwick: Energy density of the fuel: 9.6kWh/L 900 flights per day = one flight every 96 seconds 26024.706L per flight Total energy per flight: 9.6 x 26024.706kWh = 250MWh give or take = 900GJ Total power supplied from Gatwick in the form of aviation fuel: 900GJ/96s = 9.375GW. That's not only outside the range of SMRs, it's bigger than any single nuclear power station that's been built, by a comfortable margin. To make electric flight work you can't think in terms of the way the current industry is structured because it's so distorted by the energy density of the current fuel.
  - baq 3y ago
    Oof. Jet engines are 35% efficient, I'd assume electric planes would be double that, does that change the calculation? Naively I'd say we 'only' need 4.5GW?
    - VBprogrammer 3y ago
      I feel like the back of the envelope calculation must have slipped a decimal point somewhere. 9GW is approximately 1/4 of the total electrical consumption in the whole of the UK. From memory aviation as a whole is only 2% of global emissions (although it might have an extra forcing effect due to being released directly into the upper atmosphere) where as electricity generation is 20-40% of emissions.
      - baq 3y ago
        google and wolfram alpha tells me one fully tanked 737 stores 16 tons of kerosene, which translates to 261.1 GJ at 35% efficiency (72.5 MWh). doesn't sound too far off. assuming the same energy will be required for an electric airliner and you want to charge it to full in an hour... you probably need much more than 72.5MW power plant per aircraft because fast charging is nonlinear...? numbers which are hard to comprehend at scale in any case
      - regularfry 3y ago
        To paint a rough and ready picture, aviation emissions are very heavily weighted towards richer, less populous countries, whereas electricity generation (and particularly fossil fuel generation) is (to a lesser degree) tilted towards where the mass of population is: https://ourworldindata.org/carbon-footprint-flying#:~:text=We%20see%20large%20differences%20in,and%20Canada%20(168%20kg) https://ourworldindata.org/carbon-footprint-flying#:~:text=W... vs https://ourworldindata.org/grapher/carbon-intensity-electricity https://ourworldindata.org/grapher/carbon-intensity-electric.... Note that the colour axis is a log scale. It's a compounding effect: more people => more energy; poorer => worse emissions and fewer flights per capita. I thought I must have slipped a power of 10 too somewhere but if I did I can't spot it.

by gibolt 3y ago

baq 3y ago

If the tech takes off (pun intended) every major airport will need a SMR. Which is maybe good? But politically impractical today.

mlsu 3y ago
With the energy efficiency attainable by traveling in the upper atmosphere, this might be the greenest possible long range transportation. God such a tantalizing solar punk dream. I would love just to hear the inside of an electric commercial airliner at altitude.
- VBprogrammer 3y ago
  Presumably they would use something like an electrically propelled ducted fan (basically the first stage of a high bypass engine). The noise I imagine would be reasonably similar.
  - nerpderp82 3y ago
    I think a hybrid approach with a high bypass turbo fan powered by an electric motor. The fan could then switch over to a https://newatlas.com/automotive/inside-out-wankel/ https://newatlas.com/automotive/inside-out-wankel/ when at cruising altitude. Using biofuels, or carbon air capture, we get long range and a closed carbon cycle.
- _puk 3y ago
  I doubt it would be classical music and whale song playing over a beautifully calm scene.. More like kids watching movies without headphones, over loud conversations and screaming babies if other public transport is anything to go by. But we can dream!
  - SapporoChris 3y ago
    Experiences vary. I was on a Tokyo subway train (Chūō-Sōbu Line(Local)). For a couple of minutes after boarding it was so quiet that it was eerie. When I started hearing quiet noises I relaxed. Anyway, mass transit does not have to be noisy. It varies by custom and culture.
    - ryalistik 3y ago
      [dead]
oblio 3y ago
What's SMR?
- Flockster 3y ago
  I would assume a Small Modular Reactor.
regularfry 3y ago
Less of the "S". With current flight patterns you need multiple gigawatts. Calculations based on 737s leaving Gatwick: Energy density of the fuel: 9.6kWh/L 900 flights per day = one flight every 96 seconds 26024.706L per flight Total energy per flight: 9.6 x 26024.706kWh = 250MWh give or take = 900GJ Total power supplied from Gatwick in the form of aviation fuel: 900GJ/96s = 9.375GW. That's not only outside the range of SMRs, it's bigger than any single nuclear power station that's been built, by a comfortable margin. To make electric flight work you can't think in terms of the way the current industry is structured because it's so distorted by the energy density of the current fuel.
- baq 3y ago
  Oof. Jet engines are 35% efficient, I'd assume electric planes would be double that, does that change the calculation? Naively I'd say we 'only' need 4.5GW?
  - VBprogrammer 3y ago
    I feel like the back of the envelope calculation must have slipped a decimal point somewhere. 9GW is approximately 1/4 of the total electrical consumption in the whole of the UK. From memory aviation as a whole is only 2% of global emissions (although it might have an extra forcing effect due to being released directly into the upper atmosphere) where as electricity generation is 20-40% of emissions.
    - baq 3y ago
      google and wolfram alpha tells me one fully tanked 737 stores 16 tons of kerosene, which translates to 261.1 GJ at 35% efficiency (72.5 MWh). doesn't sound too far off. assuming the same energy will be required for an electric airliner and you want to charge it to full in an hour... you probably need much more than 72.5MW power plant per aircraft because fast charging is nonlinear...? numbers which are hard to comprehend at scale in any case
    - regularfry 3y ago
      To paint a rough and ready picture, aviation emissions are very heavily weighted towards richer, less populous countries, whereas electricity generation (and particularly fossil fuel generation) is (to a lesser degree) tilted towards where the mass of population is: https://ourworldindata.org/carbon-footprint-flying#:~:text=We%20see%20large%20differences%20in,and%20Canada%20(168%20kg) https://ourworldindata.org/carbon-footprint-flying#:~:text=W... vs https://ourworldindata.org/grapher/carbon-intensity-electricity https://ourworldindata.org/grapher/carbon-intensity-electric.... Note that the colour axis is a log scale. It's a compounding effect: more people => more energy; poorer => worse emissions and fewer flights per capita. I thought I must have slipped a power of 10 too somewhere but if I did I can't spot it.