parapente
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Re: Electric planes: the state of the art

Sun Dec 30, 2018 4:02 pm

Btw.
https://m.youtube.com/watch?v=gyXQhEh12Bw

This is a recent NASA hybrid BWB.Hybrid in the sense it has some conventional aspects to the shape for obvious practical everyday reasons.Forget that its conventionally powered and imagine distributed electric engines.You still get the huge unused space next to the cabin that could contain the hydrogen tanks.
 
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FredrikHAD
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Re: Electric planes: the state of the art

Sun Dec 30, 2018 4:19 pm

Waterbomber wrote:
A propeller doesn't rotate faster at altitude in real life, but let's assume that we up the RPM when air gets thinner. Soon enough, your propeller tips goes supersonic and you encounter a surge in drag, also called compressibity loss. This is why they don't do this in the first place, and instead keep the RPM and change the pitch of the props.
It's different from the airframe where you only need to think about the pressure of air flowing from one direction, the propeller itself also moves sideways which adds a dimension.

Quite correct, as far as I know, there is no "open" style propeller that can exceed the speed of sound and still keep its efficiency (but I'm no expert). One factor that needs to be considered is that the speed of sound is lower at higher altitudes (up to a point: 340 m/s at sea, 295 m/s at 10 km, FL330). Therefore, a variable pitch propeller is used in all aircraft but the simplest (right?). This is, however, not any different if you have a gas turbine or electric motor. The electric motor retains its efficiency at altitude, so we just have a massive power reserve we will never use up there.

Waterbomber wrote:
This reminds us the fact that the propeller is a major point of waste.

Why do you say that? Is the propeller (in combination with a turbine engine, say ATR72) that much less efficient than a high bypass turbo fan?

Model First flight Seats Fuel burn Fuel efficiency per seat (Wikipedia)
ATR 72-500 1997 70 1.42 kg/km (5.0 lb/mi) 2.53 L/100 km (93 mpg‑US)
Boeing 737 MAX 7 2017 128 2.85 kg/km (10.1 lb/mi) 2.77 L/100 km (84.8 mpg‑US)

Please note that there is a 20 year difference in (engine) design and still, the ATR is more efficient (and slower, I know)!!!

Waterbomber wrote:
So it's unfair to compare a turboprop which is a turboshaft with a prop attached to it, versus an AC motor without prop attached to it and say that the AC motor has a 80% efficiency while the turboprop has only 30% efficiency.

The PW127M is supposed to have just below 30 % efficiency from fuel to shaft. I think 28 % in ideal cruise is what can be achieved. If you compare that to an electric motor with some 98 % (wasn't it?) electricity to shaft efficiency, that's what needs to be used in calculations when it comes to "fuel to shaft" efficiency. If the propeller has, say 60 % efficiency, what's driving it has no relevance to its efficiency.

Electric motor 98 % x propeller 60 % = 58,8 %
PW127M 28 % x propeller 60 % = 16,8 %

Then there are other aspects in an aircraft. What needs to be considered is the real carried fuel to thrust efficiency. If the fuel is carried in batteries, you have almost no losses. If you have methanol or hydrogen and run that through a fuel cell stack, you need to factor in the efficiency of the fuel stack. I read that you can have 40 to 60 % efficiency in that stage, let's use 50 % in calculations.


Waterbomber wrote:
In short, an E-prop will convert less than 50% of the energy from batteries into work, while a modern turboprop is at around 30 from fuel.

I don't agree. Taking the PW127M as a typical example, it has 28 % fuel to shaft efficiency and multiplying that with 60 % efficiency of the propeller (see above) gets you 16.8 % fuel to thrust efficiency. The battery example will give you way more that 50 %, even including electronics.

Waterbomber wrote:
The best propellers have a 60% efficiency, AC motors performing at high torque and for prolonged times will be overbuilt and operate at 80% efficiency while gas turbines are reaching 50% efficiency.

Gas turbines in general may have have 50 % efficiency (I have not researched that), then again, I don't think you find any with that efficiency in aircraft today. Would it be feasible in a near future? Why aren't turboprop owners replacing the engines with twice as efficient ones as we speak?

Waterbomber wrote:
A word about hydrogen.
There is potential there if cost can be brought down and it is produced using renewable energy.

Again (as stated in a previous post), why does it have to be produced by renewable energy? That would be ideal of course, but as long as the sum of all environmental effects are lower, hydrogen, methanol, ethanol, "whatever"-ol is a better alternative than burning oil. If we start going electric in airliners, we'll only have one focus area left, and that is electrical power generation. It is obvious that generating clean(er) electricity at a comparatively low number of power stations is easier than taking care of pollution from thousands and thousands of aircraft engines.

Cost is another matter. I think we showed in the other thread ("Norway is to make all short-haul planes electric by 2040") that cost of creating hydrogen with the same energy content is lower than buying Jet A1.

/Fredrik
 
Waterbomber
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Re: Electric planes: the state of the art

Mon Dec 31, 2018 12:30 am

FredrikHAD wrote:
Waterbomber wrote:
A propeller doesn't rotate faster at altitude in real life, but let's assume that we up the RPM when air gets thinner. Soon enough, your propeller tips goes supersonic and you encounter a surge in drag, also called compressibity loss. This is why they don't do this in the first place, and instead keep the RPM and change the pitch of the props.
It's different from the airframe where you only need to think about the pressure of air flowing from one direction, the propeller itself also moves sideways which adds a dimension.

Quite correct, as far as I know, there is no "open" style propeller that can exceed the speed of sound and still keep its efficiency (but I'm no expert). One factor that needs to be considered is that the speed of sound is lower at higher altitudes (up to a point: 340 m/s at sea, 295 m/s at 10 km, FL330). Therefore, a variable pitch propeller is used in all aircraft but the simplest (right?). This is, however, not any different if you have a gas turbine or electric motor. The electric motor retains its efficiency at altitude, so we just have a massive power reserve we will never use up there.

Waterbomber wrote:
This reminds us the fact that the propeller is a major point of waste.

Why do you say that? Is the propeller (in combination with a turbine engine, say ATR72) that much less efficient than a high bypass turbo fan?

Model First flight Seats Fuel burn Fuel efficiency per seat (Wikipedia)
ATR 72-500 1997 70 1.42 kg/km (5.0 lb/mi) 2.53 L/100 km (93 mpg‑US)
Boeing 737 MAX 7 2017 128 2.85 kg/km (10.1 lb/mi) 2.77 L/100 km (84.8 mpg‑US)

Please note that there is a 20 year difference in (engine) design and still, the ATR is more efficient (and slower, I know)!!!

Waterbomber wrote:
So it's unfair to compare a turboprop which is a turboshaft with a prop attached to it, versus an AC motor without prop attached to it and say that the AC motor has a 80% efficiency while the turboprop has only 30% efficiency.

The PW127M is supposed to have just below 30 % efficiency from fuel to shaft. I think 28 % in ideal cruise is what can be achieved. If you compare that to an electric motor with some 98 % (wasn't it?) electricity to shaft efficiency, that's what needs to be used in calculations when it comes to "fuel to shaft" efficiency. If the propeller has, say 60 % efficiency, what's driving it has no relevance to its efficiency.

Electric motor 98 % x propeller 60 % = 58,8 %
PW127M 28 % x propeller 60 % = 16,8 %

Then there are other aspects in an aircraft. What needs to be considered is the real carried fuel to thrust efficiency. If the fuel is carried in batteries, you have almost no losses. If you have methanol or hydrogen and run that through a fuel cell stack, you need to factor in the efficiency of the fuel stack. I read that you can have 40 to 60 % efficiency in that stage, let's use 50 % in calculations.


Waterbomber wrote:
In short, an E-prop will convert less than 50% of the energy from batteries into work, while a modern turboprop is at around 30 from fuel.

I don't agree. Taking the PW127M as a typical example, it has 28 % fuel to shaft efficiency and multiplying that with 60 % efficiency of the propeller (see above) gets you 16.8 % fuel to thrust efficiency. The battery example will give you way more that 50 %, even including electronics.

Waterbomber wrote:
The best propellers have a 60% efficiency, AC motors performing at high torque and for prolonged times will be overbuilt and operate at 80% efficiency while gas turbines are reaching 50% efficiency.

Gas turbines in general may have have 50 % efficiency (I have not researched that), then again, I don't think you find any with that efficiency in aircraft today. Would it be feasible in a near future? Why aren't turboprop owners replacing the engines with twice as efficient ones as we speak?

Waterbomber wrote:
A word about hydrogen.
There is potential there if cost can be brought down and it is produced using renewable energy.

Again (as stated in a previous post), why does it have to be produced by renewable energy? That would be ideal of course, but as long as the sum of all environmental effects are lower, hydrogen, methanol, ethanol, "whatever"-ol is a better alternative than burning oil. If we start going electric in airliners, we'll only have one focus area left, and that is electrical power generation. It is obvious that generating clean(er) electricity at a comparatively low number of power stations is easier than taking care of pollution from thousands and thousands of aircraft engines.

Cost is another matter. I think we showed in the other thread ("Norway is to make all short-haul planes electric by 2040") that cost of creating hydrogen with the same energy content is lower than buying Jet A1.

/Fredrik


The PW127M is probably around 30% efficient from fuel to air displacement, not shaft. Get your facts right.

Gas turbines on aircraft are the most efficient gas turbines as they benefit from many advantages that land-based gas turbines do not benefit from.
One of the many advantages is that even the exhaust is used for thrust while on land-based gas turbines this would go to waste.
This while any other form of motors actually need to expend energy to release heat, regardless of electric or piston motor
On recent aircraft engines, the thermodynamic efficiency is already exceeding 50%.
The propulsive efficiency is moving from 60% towards 70%.

As for the cost of hydrogen, it's not lower than jet fuel for sure. Hydrogen needs to be generated from renewable sources, otherwise you will create an entire complex parallel infrastructure for nothing, with the sole purpose of competing against oil, with a doubtful economic gain. The cost of setting up infrastructure is not zero, this already exists for oil (oil vessels and pipelines for transport, refineries, storage, distribution) but it costs a fortune to setup for a new form of complex energy like hydrogen.
California mandates that 1/3rd of hydrogen be produced from renewable sources for this very reason.

What point is there to produce hydrogen from natural gas at 80% efficiency, with another 30% wasted to convert hydrogen into electricity, when you can burn natural gas directly more efficiently and using a cheap and simple internal combustion engine?
If the process would have been more efficient, electricity from natural gas would have been produced via hydrogen even if a more complex industrial setup would be needed, but it's not the case.

Hydrogen has potential to be used as a carrier/battery to carry renewable energy more efficiently. Its high power density would be an advantage for aircraft compared to batteries, even if batteries are vastly more efficient in capturing the energy.
Basically, hydrogen has the potential to carry wind, solar, hydro or any other form of naturally occuring energy in a very small package, if the cost of the entire process can be brought down.
There is potential for sure and it wouldn't surprise me if the Japanese produce a hydrogen MRJ in the future.
Japan is striving for energy independence which is the reason why they are going all-in on hydrogen.

The wikipedia page covers the challenges of hydrogen aircraft pretty well
https://en.m.wikipedia.org/wiki/Hydroge ... d_aircraft
 
parapente
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Re: Electric planes: the state of the art

Mon Dec 31, 2018 9:12 am

No doubt about it.There has to be a breakthrough in the low energy production of hydrogen or it sing never gonna happen.As above the straight maths tells you that.From what I have read there are some very interesting developments in the lab.Making the stuff is key but it also looks like a lot of progress is being made in terms of storing it as a. Liquid combined with other elements ( ammonia is one) which have very low bonding and is therefore easy to respirate out.
As discussed earlier the energy density and weight of present 'best of class' batteries is way short of what is necessary for anything commercial.
Oddly the maths shows that this is far less true of smaller aircraft/or drones. The future of short haul private ( fun) flying is very likely to go electric imho.I learned to fly on the good old Cessna.Perhaps my son will learn ( if he chooses to - no sign of it) on an electric 2 seater!
Think how quietly it will fly like thermaling in a sailplane!
 
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SheikhDjibouti
Posts: 1778
Joined: Sat Sep 30, 2017 4:59 pm

Re: Electric planes: the state of the art

Mon Dec 31, 2018 11:10 am

parapente wrote:
Yup props are best slower avoiding supersonic drag.
Yip, that would be why I suggested variable pitch and attention to propeller design to mitigate this. Perhaps I should have used a simpler word instead of mitigate - I'm not sure everybody understood it.
parapente wrote:
However I note that most electric designs have distributed engines or even embedded engines in the wing.
Obviously far far smaller props.Is this the reason they go down this route ( supersonic drag) or is there another reason?

Definitely another reason; it is a universal rule that propellers are more efficient at lower rpm. This is one of those rules that seems so obvious, it doesn't even need any math to justify it (IMO).
It isn't entirely appropriate in respect of aviation, but consider the situation with a propeller in water, at the back of a boat. A large slow moving propeller is most efficient. Spin it too fast and you suffer from cavitation.
Image

Note; I do not suggest cavitation is an issue outside of a liquid environment, but the principle of a fast spinning propeller putting too much stress on the medium, whether it be air or liquid, is something to consider. Force air to move too quickly, and you will generate turbulence, and lose energy from friction.

So, current electric designs (especially solar powered prototypes) use propellers than spin so slowly, you need a sundial to measure their rpm. :lol:
Nothing to see here; move along please.
 
parapente
Posts: 3061
Joined: Tue Mar 28, 2006 10:42 pm

Re: Electric planes: the state of the art

Mon Dec 31, 2018 1:43 pm

Re above posting.Does anybody know why many 'electric designs' including the EasyJet ones show small distributed fans often embedded in the wing or small props all along the wing.There has to be a reason as they nearly all do it,as opposed to classical large props/fans.
 
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SheikhDjibouti
Posts: 1778
Joined: Sat Sep 30, 2017 4:59 pm

Re: Electric planes: the state of the art

Mon Dec 31, 2018 2:33 pm

parapente wrote:
Re above posting.Does anybody know why many 'electric designs' including the EasyJet ones show small distributed fans often embedded in the wing or small props all along the wing.There has to be a reason as they nearly all do it,as opposed to classical large props/fans.

I do not claim to know the answer as an absolute fact, but...…
Even though Wikipedia has a page devoted to "Twinjets", it is vague beyond the obvious comment that they are more fuel efficient. They fail to state whether this is because the motors that drive the fans & propellers are more efficient as they get larger. i.e. the size of fan or propeller is a by-product of the engine behind it. There may be additional savings from having fewer throttles & gauges in the cockpit, fewer (and shorter) fuel lines, easier maintenance (especially versus tri-jets), etc

This is not necessarily the case with electric motors. Currently the most-efficient electric motor on record is a tiny device that takes 100w; about enough to power a small drone. Quite why this is the case, you'll have to wait for someone else to answer. Maybe they just haven't got around to scaling it up yet.

Meanwhile...why wouldn't you distribute the power more evenly?
This gives multi-engine redundancy (but without any penalties)(¹)
It allows shorter undercarriages (think B737 problems)
It might be beneficial in terms of less disturbance to the airflow over the wing
or, if that isn't the case
You could arrange the motors with pusher propellers, again to improve wing performance.

The Piaggio P.180 has this feature, and boasts a highly efficient wing, allowing higher cruise speed versus lower power.
The downside is engine cooling presents more of a problem, and it makes a unique noise that is not appreciated by all.
Wikipedia wrote:
the P180 has been the subject of noise complaints at airports, such as Aspen (CO) and Naples Municipal Airport, Florida, where that airport authority determined it was the noisiest aircraft using the facility. Alan Parker, chairman of the Naples Municipal Airport Authority's technical committee, described the Avanti as "irritating loud" and compared the high pitched sound "to fingernails on a chalkboard"

The P180 is said to have good fuel efficiency relative to small turbojets flying in the same speed and altitude range.
Piaggio says low-drag laminar flow is maintained to around 50% of the wing chord, compared with around 20–25% for conventional tractor turboprops where propeller wash disturbs the airflow over the wing..

The use of (multiple) quiet electric motors drivng pusher propellers would not face the same issues, but offer the same benefits.


(¹) A design featuring say 12 small electric motors would most definitely not include 12 separate throttles in the cockpit. I envisage twin throttles levers, having overall control of the six motors on each wing. Software would balance the system in the event of a single motor failing, or at least give the pilot an option to run in asymmetric mode if that was required for some reason.
Nothing to see here; move along please.
 
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FredrikHAD
Posts: 439
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Re: Electric planes: the state of the art

Mon Dec 31, 2018 4:43 pm

Waterbomber wrote:
The PW127M is probably around 30% efficient from fuel to air displacement, not shaft. Get your facts right.

Would you like me to be as rude as you are and say "YOU get YOUR facts right", or should I just show you my source? It is after all a research company that has compiled the tests and with a tiny bit of math, you can verify yourself that my calculations are correct.

Fuel efficiency for the PW120A is 26 % at take off (shaft power vs. fuel energy content) and 29 % at cruise according to the tables at the bottom of page 5 in this document:
http://www.srs.aero/wordpress/wp-content/uploads/2009/03/srs-tsd-002-rev-1-pw120a-sfc-analysis.pdf

I mistakenly said PW127M previously, but figures should be comparable for the two engine types. I have used Jet A1 as fuel in my calculations with the specific energy 42.80 MJ/kg (11.90 kWh / kg), slightly lower than Jet A (43.02 MJ/kg).


As a side note, the propeller driving the ATR72-500 (and -600) has a maximum propulsive efficiency of about 85 % according to this research paper:

Advanced Aircraft Flight Performance by Antonio Filippone (graph on top of page 166, use this link: https://books.google.se/books?id=hbsgAwAAQBAJ&pg=PA171&lpg=PA171&dq=pw127m+shaft+efficiency&source=bl&ots=ztqCW3N_zJ&sig=VwpoC0K4PYDGOCgS2p2sitvi8L0&hl=sv&sa=X#v=onepage&q=pw127m%20shaft%20efficiency&f=false )

That will, however, not affect the math when comparing electrical and gas turbine engines as the propeller is as efficient with either type. The 1:3.5 to 1:4 difference in efficiency of the motors is still there.

/Fredrik
 
Waterbomber
Posts: 849
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Re: Electric planes: the state of the art

Mon Dec 31, 2018 5:08 pm

parapente wrote:
Re above posting.Does anybody know why many 'electric designs' including the EasyJet ones show small distributed fans often embedded in the wing or small props all along the wing.There has to be a reason as they nearly all do it,as opposed to classical large props/fans.


I think that it's mainly to enable people to distinguish it as an electric aircraft more easily. It's a marketing gimmick imo. Otherwise the difference may not be noticeable to people not familiar.

It's also most likely that electrically driven aircraft will have to start with multiple engines until they can prove a certain level of reliability and be allowed to be operated as twins.
After all, AC motors fail too and turbine failure rates are so low these days that it is a justified concern whether AC motors can live up to that reliability.
In addition, unlike turbine engines, AC motors of all sizes are available off the shelf from an array of suppliers, so quality of manufacture is of concern given how critical engines are.

I think that this article sums up the reality.
https://www.google.com/amp/s/www.theatl ... le/552959/
 
Some1Somewhere
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Re: Electric planes: the state of the art

Wed Jan 02, 2019 1:43 pm

Waterbomber wrote:

The PW127M is probably around 30% efficient from fuel to air displacement, not shaft. Get your facts right.

Gas turbines on aircraft are the most efficient gas turbines as they benefit from many advantages that land-based gas turbines do not benefit from.
One of the many advantages is that even the exhaust is used for thrust while on land-based gas turbines this would go to waste.
This while any other form of motors actually need to expend energy to release heat, regardless of electric or piston motor
On recent aircraft engines, the thermodynamic efficiency is already exceeding 50%.
The propulsive efficiency is moving from 60% towards 70%.


I don't believe that's correct. The basic issue is that ground-based engines are practically unlimited in physical size and weight compared to aircraft engines.

In particular, as long as the velocity of the exhaust is higher than that of the fan/propeller, it will be more efficient to slap another turbine on and drive the fan/prop harder. Though this adds weight/cost. See the CFM LEAPs for ridiculous numbers of LPT stages...

In surface installations, they simply throw a much bigger turbine(s) on there, to extract every last drop of energy. Likewise, techniques like water injection and running the air through an intercooler between the compressor and combuster are now feasible, along with longer combustion chambers to improve efficiency and reduce NOx. Auxiliaries are no longer tightly packed etc.

GE claims the LM6000 has a thermal efficiency of 42% fuel-to-shaft, and that this is best-in-class.

A few other possible misconceptions I think should be cleared up (not aimed at you in particular):
  • Efficiencies cannot be added/subtracted; they must be multiplied. So for three stages, each with a 30% loss (70% efficient):
    • 100 - 30 - 30 - 30 = 10% Wrong
    • 0.7 * 0.7 * 0.7 = 34.3% Right
    • Note how we now have more than 3x the final efficiency.
  • With large motors, the size, weight, and losses of the necessary motor drives (VFDs/ESCs) and protection/distribution equipment (circuit breakers, busbars, fault containment, interlocking etc.) can get significant. Megawatt switchboards and motor drives can be pushing a tonne, though aircraft grade gear can presumably be built lighter at cost. And we're talking many megawatts here.
  • If you are charging a large enough number of planes, there is no point in any kind of energy storage at the airport. If you charge a plane per hour (and that's quite quiet for most large-ish airports), and it takes an hour to charge a plane... you can't spread the load out at all anyway.
  • Even if planes are infrequent, it's still likely to be cheaper to upgrade the infrastructure than to install storage equipment (storing electricity is, as we've seen, very expensive and reasonably maintenance heavy) and suffer the extra losses.
  • Electrical equipment naturally has quite significant short-term overload capabilities, as limits are largely due to copper, steel, and aluminium heating up. Typical induction motors draw 8x running current during a direct-on-line start, for example.

SheikhDjibouti wrote:
Definitely another reason; it is a universal rule that propellers are more efficient at lower rpm. This is one of those rules that seems so obvious, it doesn't even need any math to justify it (IMO).
It isn't entirely appropriate in respect of aviation, but consider the situation with a propeller in water, at the back of a boat. A large slow moving propeller is most efficient. Spin it too fast and you suffer from cavitation.
Image

Note; I do not suggest cavitation is an issue outside of a liquid environment, but the principle of a fast spinning propeller putting too much stress on the medium, whether it be air or liquid, is something to consider. Force air to move too quickly, and you will generate turbulence, and lose energy from friction.

So, current electric designs (especially solar powered prototypes) use propellers than spin so slowly, you need a sundial to measure their rpm. :lol:

Note that it's not exactly the size or speed of the prop that really matters. It's that momentum/thrust goes up linearly with mass and velocity whereas energy/power goes up linearly with mass and with the square of velocity. So moving more mass at less speed gets you the same momentum at less energy expenditure.
 
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SheikhDjibouti
Posts: 1778
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Re: Electric planes: the state of the art

Thu Jan 03, 2019 12:33 am

Now that we've all had a jolly exchange of views, perhaps we can review where we are at, as per the thread title.

The options facing us include;
1) A variety of power supply, to drive electric motors, driving either fans or propellers
a) Solar power
b) Battery Power &/or Ultracapacotors
c) On-board generation of power by Hydrogen cell, Liquid Hydrogen, or Any Other Bio-fuel.

2) A choice of airframe/wing design to accommodate either electric motors, or electric motors plus traditional aircraft engines
a) Within separate wing pods, driving individual fans or propellers.
b) Within combined wing pods driving common shafts connected to shared fans or propellers

Working examples currently include
1a) The record breaking Solar Impulse 2; solar power c/w 4 x 21 kWh lithium-ion batteries (450 kg, providing 7.5 kW (10 HP) each for night flying)Image

1b) 2016 Siemens / Extra EA-300 Aerobatic performance plane (Li-ion batteries)
Once again, my internet search has failed to identify accurate specifications and performance details, except for a 350hp motor and enough battery power to permit a 5 minute high-energy display plus 20 minutes cruise to/from the starting location. I might add that if this a/c can still perform aerobatics, it suggests there is still room on-board for additional payload in terms of batteries.
An honorable mention should also go here to Chip Yates and his electric Long Eze, (N89CY) setting numerous FAI records in 2013.
Chip Yates wrote:
“The feeling of climbing 2000 feet/min from the deck all the way to 14,500′ was unreal.


1c) 2008 Boeing Fuel Cell demonstrator (Diamond HK-36 Super Dimona; 2 seats)
Performance data is sketchy, but appears to offer 45kW at take off, and 20 kW continuous cruise, in place of the original 86kW (115hp) Rotax 914 engine.
During the flights, the pilot climbed to an altitude of 1,000 metres (3,300 feet) using a combination of battery power and power generated by the hydrogen fuel cells. Then, after reaching cruise altitude and disconnecting the batteries, the pilot maintained a cruising speed of 100km per hour (62mph) for about 20 minutes on power solely generated by the fuel cells.
Curiously, the project seemed to reach a full stop at that point, over 10 years ago.Image


Summary; none of the current specimens above represent getting even close to an airliner as they stand today.
However, small prototypes such as these were struggling into the air in 1913, but with vastly inferior performance figures. Twenty years later in 1933, the Douglas DC-1 entered service, and the rest, as they say, is history.
Nothing to see here; move along please.

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