Could you create a battery powered plane?

[essenmein]

There is Solid State Battery technology currently developing and its main problem is the cost to manufacture. They've 2.5x higher energy density than li-on types.

But I, personally, don't see the electricity as the main power source of the world. Considering the current battery tech. flying a 70 tonnes of 737 requires tremendous amount of energy and if that much of energy is packed in a battery form it would weight too much compared to fossil fuel. Specific energy of gasoline is incomparable high compared to batteries.

Second problem with electric powered vehicles is electric motors have low operational life compared to IC or Jet engines. Their maintenance is easy and low cost but in terms of operational hours I think they would require frequent maintenance when they are used in an aircraft.

Agree with everything but the last point, as far as I know electric machines far outlast IC engines and I imagine turbines as well.

If kept within operational (temperature) limits I can't think of anything that would wear out in an emachine other than bearings. There are issues with demagnetization in PM machines if over driven, but this is not really a problem if limits are observed. Where are you getting this idea from?

 

[mastermechanic]

Agree with everything but the last point, as far as I know electric machines far outlast IC engines and I imagine turbines as well.

If kept within operational (temperature) limits I can't think of anything that would wear out in an emachine other than bearings. There are issues with demagnetization in PM machines if over driven, but this is not really a problem if limits are observed. Where are you getting this idea from?

Uh, actually they're all sourced by my own experience. I observed that op-life on small DC engines. Small model aircraft DC motors have 1000 hr service life but typical aircraft engine have 15000 hr. Here you may say, "okay, wait, you're comparing a model engine dc motor and jet engine" but the point is I don't think life is not tightly linked to size so the proportion must be conserved.

The thing is you should not design an aircraft having just sufficient amount of power because in this case the engines must operate at full throttle all the time and that cause overheating, vibration etc. Then we must have much more power than needed, so while it's pretty hard to manufacture a electrical motor able to lift a Boeing 737, it's nearly impractical to manufacture a more powerful one.

 

[gleem]

Ohio Electric Motor says 15 years for AC induction motor used maintained and installed correctly. http://www.ohioelectricmotors.com/2015/07/what-is-the-average-ac-induction-motor-life-expectancy/

It is my understanding that these motors are used in EVs.

 

[mastermechanic]

Ohio Electric Motor says 15 years for AC induction motor used maintained and installed correctly. http://www.ohioelectricmotors.com/2015/07/what-is-the-average-ac-induction-motor-life-expectancy/

It is my understanding that these motors are used in EVs.

It surprised me, 15 years is quite a lot. Of course what fraction of this would remain under heavy, wet, icy , high rpm, high torque conditions? It's promising though.

 

[essenmein]

Uh, actually they're all sourced by my own experience. I observed that op-life on small DC engines. Small model aircraft DC motors have 1000 hr service life but typical aircraft engine have 15000 hr. Here you may say, "okay, wait, you're comparing a model engine dc motor and jet engine" but the point is I don't think life is not tightly linked to size so the proportion must be conserved.

The thing is you should not design an aircraft having just sufficient amount of power because in this case the engines must operate at full throttle all the time and that cause overheating, vibration etc. Then we must have much more power than needed, so while it's pretty hard to manufacture a electrical motor able to lift a Boeing 737, it's nearly impractical to manufacture a more powerful one.

Using small brushed machines with bronze bushings to extrapolate life expectancy of a electric synchronous machine with no brushes and pressure lubricated bearings is a little disingenuous. Just like for IC engines, you can build them so they last a few hundred hours (eg F1 race motors) or last nearly for ever (eg lister diesels).

That Ohio electric link says "Assuming that the motor is being operated under normal conditions, sized correctly for the application and within the manufacturer’s design requirements, it can last 15 years or more. "

Basically, IMO, just like for any machine, there is nothing inherent in electric machines that say no more than 15 years, it depends on design and how its used.

Regarding contamination ingress, salt/moisture etc, this plays havoc on any mechanical thing, neither electric or IC are somehow immune to those effects.

The problem with electric planes is not the machines, its the energy source (battery) that, barring some momentous discovery, makes them impractical IMO.

 

[David Lewis]

Not only is energy density an issue... but also charge rates so that a vehicle can get moving again in a reasonable amount of time.

That's no problem if you have multiple quick-swap battery packs.

 

[cjl]

Agree with everything but the last point, as far as I know electric machines far outlast IC engines and I imagine turbines as well.

If kept within operational (temperature) limits I can't think of anything that would wear out in an emachine other than bearings. There are issues with demagnetization in PM machines if over driven, but this is not really a problem if limits are observed. Where are you getting this idea from?

I agree that electric motors are likely to be reliable with a very long service life, but it's worth noting that turbines dramatically outperform piston engines when it comes to service life and maintenance interval (which is part of why they're popular on aircraft). They really only have 2-3 moving parts, and it's all radially symmetric and spinning smoothly rather than vibrating and oscillating all the time, so there's honestly not much to go wrong.

 

[gleem]

While conceptually simpler than piston engines fanjets are still subject to vibration and much care is required to reduce it to acceptable levels at these high rpm's. In addition they operate at high temperatures are subject to collision with intake debris so metal fatigue and damage are a concern as well as bearing wear. Although overhauls may be every 5000 hours for large engines this may cost millions of dollars per engine. https://www.avbuyer.com/articles/engines-biz-av/what-is-jet-engine-maintenance-112549

Electric motor have that conceptually simple construction and while temperature can be an issue they are protected from debris and metal fatigue. Bearings seem to be the biggest maintenance concern.

 

[mfb]

The largest area for debris is the fan which should be very similar in both cases. If I remember correctly the fan is also a common cause of catastrophic engine failure - independent of the power source for the fan.

 

[FactChecker]

I haven't reviewed all the posts on this thread, but here is a development that might be relevant. It is about an all-electric airplane being developed jointly by Harbour Air and MagniX.

 

[Tom.G]

from: IEEE SPECTRUM Jan 2020, pg 47 (SPECTRUM.IEEE.ORG)

ROLLS-ROYCE TO FLY RECORD-BREAKING ELECTRIC PLANE
"In the first quarter of 2020, Rolls-Royce will unveil ACCEL, which it says is the fastest all-electric plane ever designed."

It is a one-seat racing plane.

To break the current 3-year-old speed record of 340KPH (212MPH), they expect a speed of 480KPH, (300MPH). They state that the data acquisition rate is >20 000 points per second to optimize the actively cooled battery system.

"Look to the skies over Britain to see this plane in action."

Now THAT sounds like a bit of a project!

Cheers,
Tom

 

[anorlunda]

Now THAT sounds like a bit of a project!

agreed. It would be fun to read about the engineering of that plane.

 

[mfb]

To break the current 3-year-old speed record of 340KPH (212MPH), they expect a speed of 480KPH, (300MPH).

For comparison: Even tiny business jets fly at over 700 km/h.