8 ms·

For a battery of arbitrary weight you need to spend the same amount of energy accelerating its mass, irrespective of how much energy that battery contains.

by nvy 4y ago

mkaic 4y ago
Right, I believe GP's point is that for a given capacity, you now need fewer kilograms of batteries to store it, meaning the percentage of overall capacity used to accelerate the mass of the battery itself goes down.
buro9 4y ago
The article mentions aircraft multiple times. Once a range is achieved through available energy, reducing weight is a goal. The energy is more useful the less weight you need to move as then you can shave off a bit more weight as less energy was needed. Your car may not need this as much, an aircraft does.
- daliusd 4y ago
  Bicycles would benefit as well. I would love if my electric bicycle were slightly lighter.
  - bluGill 4y ago
    Most people should achieve far more weight loss from their belly than from their bike. But you can pay money to make the bike light and that is easier than working on yourself.
- gibolt 4y 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 4y ago
    If the tech takes off (pun intended) every major airport will need a SMR. Which is maybe good? But politically impractical today.
    - mlsu 4y 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 4y 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 4y 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 4y 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 4y 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.
- AdrianB1 4y ago
  Average plane cannot fly with batteries; the weight is still too high compared to jet fuel and the range is too short. Only short flights of up to 1000 km and 90 minutes will be in reach initially, jet fuel minus efficiency loses is still over 3000 Wh/kg, 6 times more than these new batteries.
  - VilleOr 4y ago
    Average US flight trip is about 800 km (~500 miles). If even half of all flights were powered by electricity, the impact on emissions would be huge.
    - maccard 4y ago
      Furthermore, the energy needed for takeoff is significantly higher than the energy for cruising. For an hour's flight, it's close to 50/50. The impact is disproportionately skewed towards shorter fkights
      - zirgs 4y ago
        Wondering if we could build devices that assist with takeoff - like it's done on aircraft carriers. Could save some energy that way.
        bluGill 4y ago
        We could, but it would require new aircraft. Passenger aircraft are not designed for that kind of stress. I'm not sure that passengers would like that much acceleration either. I don't know that it would actually save anything though. Aircraft of carriers are held back while they throttle the engine to full throttle. Only after the pilot is convinced the engine will run long enough to take off do they release the brakes - probably using more fuel than a regular takeoff. (the other option is to get in the air and then discover the engine isn't running and so you crash land a few meters later). I'd want a real aircraft engineer to speak to this.
        4y ago
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microjim 4y ago
Yes that’s correct. Probably a better way of articulating what I meant to say is that unlike adding more battery mass which gives you diminishing returns as that additional weight must be carried too, improvements in energy density give you gains closer to 1:1. Though in retrospect this isn’t a very interesting or insightful statement, hah.

For a battery of arbitrary weight you need to spend the same amount of energy accelerating its mass, irrespective of how much energy that battery contains.

by nvy 4y ago

For a battery of arbitrary weight you need to spend the same amount of energy accelerating its mass, irrespective of how much energy that battery contains.

mkaic 4y ago

Right, I believe GP's point is that for a given capacity, you now need fewer kilograms of batteries to store it, meaning the percentage of overall capacity used to accelerate the mass of the battery itself goes down.

buro9 4y ago

The article mentions aircraft multiple times. Once a range is achieved through available energy, reducing weight is a goal. The energy is more useful the less weight you need to move as then you can shave off a bit more weight as less energy was needed. Your car may not need this as much, an aircraft does.

daliusd 4y ago
Bicycles would benefit as well. I would love if my electric bicycle were slightly lighter.
- bluGill 4y ago
  Most people should achieve far more weight loss from their belly than from their bike. But you can pay money to make the bike light and that is easier than working on yourself.
gibolt 4y 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 4y ago
  If the tech takes off (pun intended) every major airport will need a SMR. Which is maybe good? But politically impractical today.
  - mlsu 4y 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 4y 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 4y 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 4y 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 4y 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.
AdrianB1 4y ago
Average plane cannot fly with batteries; the weight is still too high compared to jet fuel and the range is too short. Only short flights of up to 1000 km and 90 minutes will be in reach initially, jet fuel minus efficiency loses is still over 3000 Wh/kg, 6 times more than these new batteries.
- VilleOr 4y ago
  Average US flight trip is about 800 km (~500 miles). If even half of all flights were powered by electricity, the impact on emissions would be huge.
  - maccard 4y ago
    Furthermore, the energy needed for takeoff is significantly higher than the energy for cruising. For an hour's flight, it's close to 50/50. The impact is disproportionately skewed towards shorter fkights
    - zirgs 4y ago
      Wondering if we could build devices that assist with takeoff - like it's done on aircraft carriers. Could save some energy that way.
      - bluGill 4y ago
        We could, but it would require new aircraft. Passenger aircraft are not designed for that kind of stress. I'm not sure that passengers would like that much acceleration either. I don't know that it would actually save anything though. Aircraft of carriers are held back while they throttle the engine to full throttle. Only after the pilot is convinced the engine will run long enough to take off do they release the brakes - probably using more fuel than a regular takeoff. (the other option is to get in the air and then discover the engine isn't running and so you crash land a few meters later). I'd want a real aircraft engineer to speak to this.
        4y ago

deleted 4y ago

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deleted 4y ago

[deleted]

microjim 4y ago

Yes that’s correct. Probably a better way of articulating what I meant to say is that unlike adding more battery mass which gives you diminishing returns as that additional weight must be carried too, improvements in energy density give you gains closer to 1:1. Though in retrospect this isn’t a very interesting or insightful statement, hah.