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E-Fan X: R-R/Airbus electric drive demonstrator

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E-Fan X: R-R/Airbus electric drive demonstrator

Old 28th Nov 2017, 13:33
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E-Fan X: R-R/Airbus electric drive demonstrator

Airbus, Rolls-Royce, and Siemens team up for electric future ? Rolls-Royce

This looks interesting. Airbus, R-R, and Siemens developing an electric demonstrator aircraft. Specifically, the airframe is a BAe 146 with one engine replaced with a ducted electric fan. The power comes from a 2MW turboshaft generator in the tail - like a big APU (IIRC that's in the same ball park as the 787's electrics). Once that's working they'll swap a second engine.

Questions I have about this:

1) Is the efficiency gain that good it's still worthwhile when the power is coming from a gas turbine?
2) Or is the idea to prove the power electronics and the fan, with a view to getting the power from something else?
3) Are they thinking of a duty cycle change - take-off on turbofan and cruise on turboelectric?
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Old 28th Nov 2017, 13:39
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A bit more detail: https://www.siemens.com/innovation/e...y-e-fan-x.html
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Old 28th Nov 2017, 15:45
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The key seems to be that the on-board generator is designed only to provide enough power for cruise. Take-off and climb will have this generator's power supplemented by LiIon batteries. This means that because the generator will always operate at full capacity, it can be much more weight-efficient than one that is required to handle the peak loads associated with take-off and climb.
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Old 28th Nov 2017, 15:58
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That makes a lot of sense.
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Old 28th Nov 2017, 21:38
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Before one can run, it must crawl, stand, walk and then maybe take a few running steps. This maybe just a start, but at least some are experimenting with new innovations. Lets, let them start with a slow crawl or even belly drag.
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Old 29th Nov 2017, 00:25
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Fascinating. This could be the future of more efficient fan-based propulsion.

The real challenge is commercial aviation moving away from fossil fuels, but for the time being, the potential power to weight ratio (not to mention cost) of a gallon of kerosene is hard to beat.
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Old 29th Nov 2017, 01:07
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Assuming the batteries are rechargeable, what's the cost of joules per hour compared to gallons per hour in a fan drive?
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Old 29th Nov 2017, 04:04
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Interesting question, Lomapaseo. I do not have an exact answer, but I do know that kerosene contains 100 times the energy by weight compared to electric storage batteries. We all know weight is of primary importance when considering things airborne.

I can tell you current (Tesla) battery manufacturing prices are around $200 per kilowatt hour. Consider the current price of kerosene, and the fact that one gallon is equivalent to around 40 kilowatt hours of energy and the scope of the challenge becomes more apparent.

Consider it takes around 90 megawatts to get a typical 747 in the air, the cost of batteries powering the original jumbo, if we set aside the enormous weight penalty, is quite staggering - $200x90,000 = a very large figure - and that's just to get airborne.

Of course those batteries are rechargeable, but the initial capital cost buys a lot of liquid fuel and thus we remain plying the skies on carbon based fuels for the foreseeable future, again leaving aside the weight problem.

Not trying to be a totally negative Nancy, as I feel renewable power is our best bet for the future, but consider this: An operational reality that is often left out of discussions involving battery powered aircraft is weight. A lesser, yet consequential aspect of that weight is how a conventionally powered aircraft gets lighter and more efficient as the fuel is consumed, while battery powered aircraft land at nearly the same weight that they took off - after power is depleted, the battery dead weight remains the same.
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Old 29th Nov 2017, 05:19
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I imagine much useful data will be gained with this test bed. But for the most part...Greenwashing.
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Old 29th Nov 2017, 07:06
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Originally Posted by lomapaseo View Post
Assuming the batteries are rechargeable, what's the cost of joules per hour compared to gallons per hour in a fan drive?
When much of the charge for takeoff N comes from descent N-1, that joules per hour cost (negating capital costs) looks great. That it also set's you up nicely for a go-around is just icing on the cake.
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Old 29th Nov 2017, 07:51
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vapilot2004

No disagreement from me, but I do think that you also need to take into account losses. The thermal efficiency of an aircraft turbofan is pretty poor compared with an electric motor....empirically stated a 100kWh Tesla can easily drive 300 miles. Try that on 2.5 gallons of Kerosene or gas.
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Old 29th Nov 2017, 09:06
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An electric 146

Good grief, an electric 146 !
Having witnessed the project from start to finish, it continues to surprise with the range of new uses; met research, firefighting, etc.
The wing - engine pylon geometry is ideal for this type of testing, which together with the aircraft’s twin hyd/elect systems and a four engining configuration should minimise problems and maximise opportunity. It should also be possible to test a range of different motor/fan sizes with the same installation as well as relatively large size open-rotor configuration.

As for the weight - cost debate, the reduced complexities of the power plant - optimisation of the gas path, no high temp metals, turbine containment, lower overall weight, could offset a considerable part of a battery installation.
Then there could be many advantages from not requiring a ‘wet wing’, reduced weight, ease of manufacture, fuel piping, pumps, and system integrity and isolation, ...

No wonder that the big players have made a significant move in the testing of future systems.
And perhaps an even quieter, quiet 146.
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Old 29th Nov 2017, 22:05
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Originally Posted by vapilot2004 View Post
I can tell you current (Tesla) battery manufacturing prices are around $200 per kilowatt hour. Consider the current price of kerosene, and the fact that one gallon is equivalent to around 40 kilowatt hours of energy and the scope of the challenge becomes more apparent.

Consider it takes around 90 megawatts to get a typical 747 in the air, the cost of batteries powering the original jumbo, if we set aside the enormous weight penalty, is quite staggering - $200x90,000 = a very large figure - and that's just to get airborne.
Well, the batteries only need to supply that 90 MW during climb (and climb power is lower than take-off power), so you can drain the batteries with 90 MW in about 10 minutes, requiring a 15.000 kwh battery, which would cost about 3 million dollar at your quoted price. Not that much compared to the list price of a 747.
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Old 29th Nov 2017, 22:16
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Originally Posted by vapilot2004 View Post
Consider it takes around 90 megawatts to get a typical 747 in the air,
Translation.... "I havent a clue what i am talking about!"

thats megawatthours? megawhatseconds? megawhattheforknanoseconds?
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Old 29th Nov 2017, 22:59
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he quotes time and power.
multiply that and you get the energy of the 15 MWh he sized the battery at.

now how much does this 15 MWh battery weigh is a interesting question.

now the wording might not be perfect but it's quite clear.
on the other hand people saying this windmill prodcues 1 MW per year now that is stupid.

oh and Translation:
"reading comprehension: not so good"
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Old 30th Nov 2017, 00:23
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you are referring to a later post where the value is estimated as 90megawatt for 10 minutes .... exactly the point I was making! not that i agree with that estimation, the get off the ground value will be significantly greater than the climb away value.

But there are several other possible gains
1 fan speed can be optimum without gears
2 contra rotating fans also can be achieved very simply without gears
3 and finally for getting off the ground "ludicrous" amount of power available for short bursts and this power is instantly available without any turbine lag which is a good thing for a go around.
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Old 30th Nov 2017, 00:43
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still an hour worth of power to get "airborne" is still reasonable if you want to include the climb

but yeah you are right i misunderstood because the quoted part was put in a better context in another post.

anyway estimating the cost of the batteries is the wrong approach.
especially because you are assuming power needed to get the plane off the ground with the current powerplant+fuel. with all the heavy batteries you have significantly lower useful load.

weight of a 15 MWh lithium ion battery assuming 300 Wh/kg:
a whopping 50 000 kg or 110 000 lbs
payload of 747 freighters is around 120 000 kg.

this should make it clear how ridiculous the idea is with current batteries sometimes i think people just don't get that. or maybe they do what do i know
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Old 30th Nov 2017, 00:59
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Most of this "green" is just marketing, sounding eco-friendly to the gullible.
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Old 30th Nov 2017, 01:58
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I don't think wet wings are gone just yet. A big benefit of this is the ability to move away for standard design. The fan would basically be an overgrown hairdryer (Wasn't there a joke about 146s being powered by 4 hairdryers or was that 4oil leaks connected by an electrical fault?).
You could put the generator anywhere in the aircraft's structure to optimise design. For a 146 you could potentially power 4 fans from 1 big generator or two smaller generators to allow for redundancy. I think batteries should only be carried for the power plant to reduce lag for quick spool-up times.
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Old 30th Nov 2017, 07:28
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Originally Posted by safetypee View Post
Then there could be many advantages from not requiring a ‘wet wing’, reduced weight, ease of manufacture, fuel piping, pumps, and system integrity and isolation, ...
Unless you're suggesting that it's a perpetual motion machine, the fuel to power the turbine generators is still going to have to be accommodated somewhere.
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