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N707ZS
21st Sep 2018, 06:58
https://www.msn.com/en-gb/money/entrepreneurs/how-the-promise-of-electric-power-could-transform-aviation/ar-BBNudEm?ocid=spartandhp

At low power a set of pedals comes up under each seat! Or perhaps not first class seats.

treadigraph
21st Sep 2018, 08:26
I thought you meant one of these! :)

https://cimg9.ibsrv.net/gimg/pprune.org-vbulletin/232x217/plane_d04762765b9a4d82b4f9c6ecfdef21bfc9719445.jpg

57mm
21st Sep 2018, 09:54
What happens to an electric aircraft in flight suffers a lightning strike?

PJD1
21st Sep 2018, 10:36
What happens to an electric aircraft in flight suffers a lightning strike?

Same thing that happens to any aircraft I would imagine (which is usually not very much). Most aircraft rely on electrical systems for many things and are often struck by lightning with no adverse effects, why would this be any different?

Tankertrashnav
21st Sep 2018, 11:44
treadigraph :D

N707ZS
21st Sep 2018, 13:40
What happens to an electric aircraft in flight suffers a lightning strike? Perhaps it would go faster!

treadigraph
21st Sep 2018, 13:59
A lightning strike - that's when everybody walks out!

ethicalconundrum
21st Sep 2018, 20:17
“Batteries have an energy density 60 times less than kerosene (jet fuel),”

This should have been in the first paragraph, above all the graphics and fancy future ideals, not stuck way down at the end. Battery(only) powered airplanes will never be more than a tiny niche in the aviation market. Hybrids may come along, but if one looks at the percent of total motive force in a hybrid provided by electric and not liquid carbon based fuel, it will be vanishingly small. I have two Prius C hybrid cars. The latest generation from the originator of the hybrid vehicle, and the percent of power delivered from the battery runs about 8% or less for nominal trips that one uses a car.

I could see a electric motor driven by battery to provide some thrust for take off, and recover it during descent, but the craft will always, always need to be able to climb and run on gas, albeit maybe at a lesser rate(vert speed). Other than that, battery powered flight is a pipe-dream. Lets not forget, we are usually burning tons of coal, or oil to recharge the battery as well. they don't magically charge themselves.

DaveReidUK
21st Sep 2018, 20:52
I could see a electric motor driven by battery to provide some thrust for take off, and recover it during descent, but the craft will always, always need to be able to climb and run on gas, albeit maybe at a lesser rate(vert speed). Other than that, battery powered flight is a pipe-dream.

e-Genius sets seven world records for purely electric powered aircraft (https://www.kasaero.de/en/58-e-genius-sets-seven-world-records-for-purely-electric-powered-aircraft)

ethicalconundrum
21st Sep 2018, 21:09
e-Genius sets seven world records for purely electric powered aircraft (https://www.kasaero.de/en/58-e-genius-sets-seven-world-records-for-purely-electric-powered-aircraft)

" Battery(only) powered airplanes will never be more than a tiny niche in the aviation market. "

Thank you for confirmation of my statement.

ethicalconundrum
21st Sep 2018, 21:19
To me, the main feature of the electric vehicle is the ability to recover energy and not waste it all as heat in the brakes. I like the idea of a turbine/generator/electric motor hybrid for that purpose (yes, it's being done) so the vehicle is completely electric traction with a portable charger, but I can't quite see the same application for aircraft because there is little scope to recover energy so why bother with the inefficiency of the intermediate conversion to electricity?

Electric traction has benefits, as you've noted. Trying to engineer the conversion of the energy is a large job. Most US train engines are: Diesel engine -> Generator -> Traction motors -> Wheel trucks. But - I must point out that a US diesel electric locomotive weighs in at about 400,000 Lbs. Hauling around large copper coils of generator and traction motor just isn't going to work in most planes. A compromise which is being used in most hybrids is an old design that goes back to the origins of electric motors. They are called 'dynamo', and it operates in two modes. In one mode, it is a generator when driven by a prop, or a moving car, or anything else. In another mode, the same thing will operate as a traction motor, doing double duty. We're learning a lot about making dynamos more efficient at the very different jobs they do, and hopefully it can be expanded somewhat to the airplane mode.

megan
22nd Sep 2018, 03:50
In one mode, it is a generator when driven by a prop, or a moving car, or anything else. In another mode, the same thing will operate as a traction motor, doing double dutyStarter/Generator fitted to lots of turbine aircraft.

ethicalconundrum
22nd Sep 2018, 04:38
Most (if not all) of the modern ones are brushless DC motors, because the commutator in early motors wouldn't last long with that sort of use. The control electronics is what makes it - I've handled large water-cooled IGBT power modules that are used for this - I ought to note that in a previous job I worked on electric powertrains for trucks. Cars and trucks, you're typically talking in the tens of kW up to about 500kW, trains are up into the megawatt range. I can just about lift one 100kW motor. 18" long and about 8" diameter to give an idea of scale. I guess for a single prop aircraft that's enough, you'd have to figure out the weight of the engine and replace it with that motor, possibly a gearbox (motor works more efficiently at higher speed so would need gearing down) and batteries. The batteries are what takes up the space and weight.

Thanks, I was trying to keep it fairly simple for the audience. Not everyone has the background. The article was talking about 100 pax planes powered by battery driven motors. I haven't done the power calcs, but we're talking a few KW here to move something like a MD-80 through the air with just batts. Sure, once can add a few cells, and a motor to a sailplane(e-genius) and with a glide ratio of about 30:1, make some headway. But - again, the article is talking about a payload generating comm aircraft. Frankly, I'm not seeing it, just due to the poor energy density. Even with the improved thermodynamic efficiency of a brushless DC motor.

Cheltman
22nd Sep 2018, 10:29
The 60:1 difference in energy density is only part of the issue. Obviously as a kerosene fuel plane flies it gets lighter. A simple electric one does not. For any reasonable flight length the energy density for batteries needs to be improved by a lot more than 60. I guess the other calculation to do if you are bored is recharge process. Guess you could refuel a commercial airliner at 100 tonnes an hour? Work out what that is in KW. Not convinced that simple electric is the right route forward.

david1300
22nd Sep 2018, 22:27
I think the battery issue can be overcome if we just develop long enough extension leads so the plane is able to stay plugged in to mains

treadigraph
23rd Sep 2018, 00:42
I think the battery issue can be overcome if we just develop long enough extension leads so the plane is able to stay plugged in to mains

Elasticated flex is what you need. Stretch it far enough and you could benefit from something similar to what NASA term a free return trajectory.

WingNut60
23rd Sep 2018, 00:51
Most (if not all) of the modern ones are brushless DC motors, .........

I have not worked around locomotives for a very long time, so do not know.
But I do know that most (all) modern electric mining trucks use brushless AC motors.

As I mentioned in an earlier thread, another factor in the weight game with such systems is the control gear (VSD drives). Even using IGBT's the weight of the control gear is not that far behind weight of the motors. And then you have cooling for the control gear and the motors. Not a real problem in a mining truck.

Still a fair way to go yet.

As for the e-Thingie, except for the ascent phase, how do those records stack up against those for any similar glider?

Um... lifting...
23rd Sep 2018, 01:19
Most successful electric propulsion systems, regardless of AC or DC or be they in ships, submarines, locomotives, or trucks, or whether the chemical energy used to provide the electrical potential is petroleum, coal, or nuclear share one particular trait: they don't have to overcome gravity simply to operate (yes, to climb hills, certainly, but not to enter their operational milieu)

I've seen and worked with large shipboard AC and DC motors aboard ship. Icebreakers, primarily, where the weight of all the various components is an asset, though I've seen them on buoy tenders and a few other ship designs that require the ability to reverse shaft rotation frequently.

I recollect there are also AC and DC motors propelling locomotives, depending upon the design philosophy of the manufacturer and the end use, though I may be mistaken there.

Nuclear aircraft propulsion was investigated by the U.S. Army Air Forces in the late 1940s into the early 1950s. Whether it's ever been worked upon more recently I haven't any idea, but I suspect those files are still in a cabinet somewhere.

Aircraft Nuclear Propulsion (https://en.wikipedia.org/wiki/Aircraft_Nuclear_Propulsion)

While servo motors are used often these days to power control surfaces and the like, I suspect battery technology needs another 6 or so iterations of whatever the battery equivalent of Moore's Law is before it's practical for propulsion in aviation.

WingNut60
23rd Sep 2018, 01:58
Most electric haul trucks have gone over to AC because of improvements in :

Efficiency
Controllability
Reliability
Retard capability (without touching the brake AC trucks will retard down to 1 - 2 km/h)

Most current retard systems are total loss, just heating up grid resistors.
However manufacturers (Siemens, Hitachi, GE, etc.) are actively working on energy recovery systems.
Not sure about locos but I'd be surprised if they were not headed the same way..

gemma10
23rd Sep 2018, 15:38
I thought this was a battery powered airplane.https://upload.wikimedia.org/wikipedia/commons/thumb/e/e7/AA_Flagship_Freedom.JPG/220px-AA_Flagship_Freedom.JPG (https://en.wikipedia.org/wiki/File:AA_Flagship_Freedom.JPG)

jimtherev
23rd Sep 2018, 19:13
Goodness! 23 posts so far, and no-one has mentioned a conveyor belt.

abgd
23rd Sep 2018, 20:53
I am also sceptical about electric airliners in the near future, but I can imagine electric power playing a role - particularly for aircraft operating over shorter routes, or for hybrid designs.

Brushless motors are much more efficient than jet engines - should be well over 90% whereas jet engines will be at least 2-3 times less efficient so although the energy density of a battery is much lower than that of AVTUR, your shortfall is likely to be much less than 60x.

Although the energy density of a battery is low, the power density of a battery and electric motor can be much higher than that of a jet engine so VTOL or VSTOL becomes possible. You could also reduce the wing in size for a more efficient cruise.

Airliners are also less efficient than they could be, in part because of their need to be able to climb on one engine whilst fully loaded at take-off. Electric motors scale well and need little maintenance, so there's no real reason not to have lots of relatively small motors. If you had a hybrid system where if the AVTUR powered engine failed, you could still do a few circuits on electric power alone, you might be able to make do with a single turbine engine which would greatly reduce operating costs. It's also tricky to make jet engines that are efficient at all altitudes, so you could gain by using electric power for take-off, then using a turbine engine to recharge the batteries in the cruise and to power the aircraft in the cruise.

Electric aircraft can be very quiet which is obviously a good thing for transport between urban centres.

The mistake is to think that an electric airliner would just be an electrified version of an existing airliner, flying the same routes. We're not too far off being able to make electric or hybrid airliners that could fly smallish numbers of people for a few hundred miles at a time, but they would be very different from what we're used to. Getting such an aircraft certified would be another matter.