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London-Paris electric flight 'in decade'

bbc.co.uk

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Re: London-Paris electric flight 'in decade'

#51

Post by ptaipale »

alex_duf wrote: post #28
ptaipale wrote: post #11

TL;DR: If I read things right, the BBC article is highly misleading and the plane still uses jet fuel. Longer version: The article mentions "removing the need for jet fuel" but does not explain how the engines of this "electric" plane work. Propellers run by electric motors, or what? No. Wright Electric's own site is scant on technical details and concentrates on praising the great team in its blog. From browsing oth…

I think the image you can see on the electrek article is from this blog post: https://weflywright.com/2017/02/12/wright-weekly-weport-feb-... The legend for that image is: >This image shows the potential subsystems that could be powered electrically. (Note: an fuel plane can also install electric subsystems – for example the 787 is making headway in this direction – but the subsystems in an electric plane will be all…

Ok. Maybe I was too sceptic.

However, I'd expect a competent tech journo to make some questions and write about how the electric plane actually works.

Re: London-Paris electric flight 'in decade'

#52

Post by lorenzhs »

notahacker wrote: post #29
thriftwy wrote: post #10

What's the point if you can just take an electric train? Isn't it basically 'a flight' on rails? They should have chosen a better city pair.

Tell that to the double-digit number of airlines already flying between London and Paris... It's a [hypothetical] aircraft, not a hyperloop. It can fly other routes.

Eurostar have around 80% market share on Paris–London for good reason. At 2hrs 15mins from city centre to city centre it's faster, less hassle, and more comfortable than flying. Security is less strict (you can take liquids) and you don't have to check your bags. Two large items of luggage are also included for every passenger. It's not even more expensive than flying if you book in advance if you include the price for airport transfer.

London–Paris is just an example in the article to demonstrate the range of that hypothetical aircraft. It could also be useful as a demonstrator.

Re: London-Paris electric flight 'in decade'

#53

Post by neolefty »

blutack wrote: post #25
tankenmate wrote: post #8

Earlier quoted context omitted.

The equation isn't just energy density; it's also the efficiency of harnessing that energy. Good electric motors are way more efficient than a turbofan.

Electric motors would need to be orders of magnitude more efficient than turbofans (which they aren't). You also need to compare the overall efficiency developed as thrust, not just thermal efficiency. There's also the issue of the mass of batteries not going away during the flight, unlike fuel, which will require maximum landing weight to equal maximum takeoff weight - this will impose a structural penalty versus IC…

Maximum efficiency is ... 100%. So if a turbofan is 30% efficient, then the best you can do is about 3x.

Re: London-Paris electric flight 'in decade'

#54

Post by jlebrech »

charlesdenault wrote: post #38
jlebrech wrote: post #18

we could save a lot on fuel if they reordered flight plans into a grid, you might not be going direct to somewhere far and popular but they overall impact or the environment would be huge.

What do you mean by a grid? Long-haul direct flights offer many benefits, such as lower drag at cruising altitude, engine efficiency at altitude, etc. [1] Biggest fuel savings are going to come from more efficient engines and weight reduction (composites). 1: https://en.wikipedia.org/wiki/Fuel_economy_in_aircraft

you find the optimal distance for a flight and create a mesh out of those flights. and stop lines from crossing.

Re: London-Paris electric flight 'in decade'

#55

Post by notahacker »

Retric wrote: post #50
notahacker wrote: post #33

Earlier quoted context omitted.

Not when you're dependent on (i) aviation authorities to certify your aircraft and (ii) third parties to improve battery technology to the point where it can happen

Based on another article they are not doing 100% electric. They are basically using battery's to replace the alternator/APU attached to the jet engine. That still adds up to a lot of jet fuel, but is only something like 5% total fuel savings.

That's a little more achievable than the "zero emissions airliner" their website promises and would explain why they're talking about going after the A320 market rather than the ATR one (And a 5% emissions reduction over a 10 year horizon is only half what engine suppliers aim for by improved jet technology, though if it's on top of that improvement it would still be very welcome)

But if what they're building is an APU rather than a new means of propulsion involving radical wing redesigns, I'm not sure why they're talking about building their own airframe rather than getting it certified to go onto the next generation of other manufacturers' airframes

Re: London-Paris electric flight 'in decade'

#57

Post by notahacker »

JustSomeNobody wrote: post #36
fdej wrote: post #26

Earlier quoted context omitted.

That's correct, but note that an electric motor is about twice as efficient as a combustion engine, reducing the factor to about 25x (at least ideally). Typical medium range aircraft burn about 3 kg fuel per km [1], so to fly 1000 km you would need about 3 * 25 * 1000 kg = 75 tonnes of batteries. This should be in the ballpark of what we can pack into an aircraft already, but I guess at least another 2x improvement i…

What's the turnaround for the aircraft though? If they can't turn around an aircraft in 15-30 min, we'll need more aircraft or prices will skyrocket (no pun).

Any sensible proposal for electric systems for commercial aircraft is going to aim for batteries to be safely swappable in 10-15 minutes. (Though they can still make delays from unexpected diversions to airports without a stock of batteries worse)

Re: London-Paris electric flight 'in decade'

#58

Post by rwmj »

JustSomeNobody wrote: post #36
fdej wrote: post #26

Earlier quoted context omitted.

That's correct, but note that an electric motor is about twice as efficient as a combustion engine, reducing the factor to about 25x (at least ideally). Typical medium range aircraft burn about 3 kg fuel per km [1], so to fly 1000 km you would need about 3 * 25 * 1000 kg = 75 tonnes of batteries. This should be in the ballpark of what we can pack into an aircraft already, but I guess at least another 2x improvement i…

What's the turnaround for the aircraft though? If they can't turn around an aircraft in 15-30 min, we'll need more aircraft or prices will skyrocket (no pun).

Supercapacitors could solve that, but unfortunately they currently have much less density even than batteries. Apparently graphene supercaps may solve that, but not at the moment.

Re: London-Paris electric flight 'in decade'

#59

Post by polshaw »

koolba wrote: post #2

I'm not at the forefront of this field so maybe I missed some great advances in battery technology or airplane efficiency, but how could this possible work when the energy density of a battery (.3-.9 MJ/kg) is 50x less than that of jet fuel (46 MJ/kg)[1]? Or is that simply enough for (very) short haul flights? [1]: https://en.wikipedia.org/wiki/Energy_density

Yes the idea for this will be v. short haul for now which is why they talk about London to Paris; ~215 miles. 25 times further (50x lower energy density, 2x better engine efficiency) would be under 5,400 miles.

Looking at the empty weight, the weight of max fuel capacity and range[1], it seems realistic to fly 200-300mi on batteries without any kind of jettisoning.

So it seems feasible, the next question is where could it be in terms of commercial viability.

1. https://en.wikipedia.org/wiki/Boeing_777

Re: London-Paris electric flight 'in decade'

#60

Post by wlll »

JustSomeNobody wrote: post #36
fdej wrote: post #26

Earlier quoted context omitted.

That's correct, but note that an electric motor is about twice as efficient as a combustion engine, reducing the factor to about 25x (at least ideally). Typical medium range aircraft burn about 3 kg fuel per km [1], so to fly 1000 km you would need about 3 * 25 * 1000 kg = 75 tonnes of batteries. This should be in the ballpark of what we can pack into an aircraft already, but I guess at least another 2x improvement i…

What's the turnaround for the aircraft though? If they can't turn around an aircraft in 15-30 min, we'll need more aircraft or prices will skyrocket (no pun).

Tesla style battery swap perhaps?
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