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.
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.
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.
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.
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.
That's assuming an overnight switch from what we have to all electric, for one of the busiest airports in the world.
Thinking in terms of disruption (from the innovator sense), their top 3 destinations [0] are Dublin, Barcelona and Malaga. Skipping barcelona becauese it's as busy, I don't think it's out of reach to consider that a 737 could do a return trip to dublin or Malaga without charging.
Another perspective is that taking off is significantly more energy intensive than cruising. According to [1], takeoff is equivalent to an hour of cruising. One way of looking at this is it only makes sense for mid haul travel instead. If we replaced transatlantic flights, or similar (us to Europe maybe) the savings would be immense and significantly more achievable
Yep. The thing is, even if you divide the power needed by two (by being smart about which planes you charge, or by how much) and then by two again (for a smaller airport) you still need a full new power plant to supply it. It's well out of SMR territory.
The way you'd have to do it is something like the Tesla approach: put small charging stations for luxury planes in as many airports as possible (because nobody, but nobody, will fly a plane into an airport they can't fly out of), and build out from there. That way you can do something financially interesting at SMR scale, and build momentum for the next step on something marketed as aspirational. Because the hardest SMR to build will be the first. Once you've got one, installing a second should be an easy sell. And two leads to four, and so on and so forth.
This is, of course, making the further assumption that something can be done about charging times. Getting 90GJ into a 737 currently takes about 23 minutes. That's 65MW, which is a nontrivial problem to solve all on its own; anything that slows down the recharge means longer queues to turn around, which, one way or another, means more land area or fewer flights for the airport, and worse economics for the operator.
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?
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.
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.
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/ when at cruising altitude. Using biofuels, or carbon air capture, we get long range and a closed carbon cycle.
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.
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.
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.
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
No. It is not the takeoff as in "raising the wheels from the tarmac" part that is consuming most energy, but reaching the flight altitude. Real case, with smaller plane, I take off in 300 meters in less than 30 seconds at max power, than raise to 3000m in more than 10 minutes of 90% power. That makes the assisted takeoff less than 10% of the energy to get to cruise altitude.
I don't have the numbers for a jet fighter on a carrier, but I think it is in the same range. The takeoff assist is not for saving fuel, but to allow takeoff at the loadout of the plane that would require otherwise a longer runway or lighter loadout (less fuel and weapons).
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.
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.