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Cool! What didn’t occur to me until I learnt it was that you get a multiplicative benefit with energy density when weight is a major factor (air transport, espe
by microjim 3y ago
Cool! What didn’t occur to me until I learnt it was that you get a multiplicative benefit with energy density when weight is a major factor (air transport, especially) because you need to spend less energy accelerating mass used by the battery itself.
- nvy 3y agoFor 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.
- deleted 3y ago[deleted]
- mkaic 3y agoRight, 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 3y agoThe 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 3y agoBicycles would benefit as well. I would love if my electric bicycle were slightly lighter.
- bluGill 3y agoMost 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 3y ago500-600 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 agoIf the tech takes off (pun intended) every major airport will need a SMR. Which is maybe good? But politically impractical today.
- mlsu 3y agoWith 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 agoPresumably 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 agoI 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 agoI 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!
- AdrianB1 3y agoAverage 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 3y agoAverage 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 3y agoFurthermore, 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 3y agoWondering if we could build devices that assist with takeoff - like it's done on aircraft carriers. Could save some energy that way.
- bluGill 3y agoWe 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.
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- microjim 3y agoYes 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.
- heywhatupboys 3y ago0,01 % maybe
- mcapodici 3y agoSame with jet fuel on a plane. They calculate the amount to fuel carefully to be efficient but safe. Too much and the plane is heavier and uses more fuel. Too little and you might run out if put into a holding then diverted. Obviously jet fuel is what it is it wont get more dense but a more efficient engine means less fuel needed means even more efficiency and so on.
- NovaDudely 3y agoIt was something I had never considered but it is wild to think about. I believe it was Vaclav Smil that highlighted it to me. On its longest trip an A380(I think?) takes off weighing 400 tons and lands weighing 200 tons. That kind of thing is just cool to ponder.
- 0xFF0123 3y agoRockets reaching orbit are an interesting example too.
- ryan93 3y agoIt is literally insane how much oil there is. Planes use i think less than 10% of world oil consumption.
- arwhatever 3y agoI realized while working on heavy transport aircraft that they their weight can be (very roughly) 1/3 aircraft, 1/3 fuel, and 1/3 cargo, and being struck by how different these proportions are from the family sedan.
- MaxMatti 3y agoNot only that but too much might also cause you to have to dump fuel in order for the plane to be able to land.
- Swannie 3y agoThe Qantas 16h 45m flight from Dallas to Sydney aims for Brisbane, and then turns to Sydney as the plane approaches Australia. (10th longest commercial route in the world). This allows the plane to land at Brisbane and refuel if the calculations are done wrong. Couldn't find stats on how many times it's had to land in BNE. Pre-COVID, it was apparently common to try and off-load passengers to single stopover flights to reduce fuel needs (I was one of those passengers, and the crew confirmed it was a regular occurance).