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Electric Powered Aircraft

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Electric Powered Aircraft

Old 14th Apr 2019, 21:03
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Originally Posted by pattern_is_full
"I tol' Wilbur, and I tol' Orville - it just won't fly!" Famous last words.....
Fake news proves nothing but says a lot. If you want to prove a point, stick to the science.
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Old 14th Apr 2019, 22:59
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Originally Posted by Reacher19
There was an article this week on the BBC website regarding a German company that believe they have developed a battery that no longer relies on the heavy metals that are hard to source and that will give approx. 600 miles on a single charge. Estimate was for a production model within 5 years.

Technology is always getting better and I think an electric car in the mid 20s will outrun a Diesel engine with ease so an electric plane within 10-15 years should be feasible.

Haven’t EasyJet set themselves a target to fly an electric plane by 2028?
I used to follow EV technology a bit. It's almost cliche that announcements of "game-changing" developments in battery technology are made by research groups, and then that's the last you ever hear about it. Believe it when it's for sale or being used in production vehicles.
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Old 14th Apr 2019, 23:54
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Use as a trainer makes some sense for a battery aircraft - relatively short flights that generally return to the departure airport to get recharged for the next lesson.

Long range intercontinental transport is a completely different story. Given foreseeable technology, biofuels are the way forward. I saw an interesting paper roughly ten years ago about jet fuel from algae - they were already able to produce biofuel from algae that was nearly indistinguishable from Jet A. It has a number of advantages over vegetable oil based fuels - it required a small fraction of the land area, the algae literally ate sewage, and required much less processing than vegetable oil based fuels. While not quite carbon neutral, it was pretty close (much closer than any other proposed bio fuel). At the time Boeing was a participant in the study.
At the time, the biggest drawback to large scale production was it required large amounts of fresh water, but they were working to develop an algae variety that would work with sea water. That and of course cost - it need petroleum to sell for over $100/barrel to be economical.
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Old 15th Apr 2019, 02:35
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As above - going into production it seems, : Bio Jet fuel but using some waste oil? (Vegetable?)

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Old 15th Apr 2019, 03:18
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Originally Posted by Imagegear
As above - going into production it seems, : Bio Jet fuel but using some waste oil? (Vegetable?)

IG
The linked article says jetfuel and biodiesel - I'd bet the waste (vegetable) oil will go to biodiesel, not jet fuel (biodiesel doesn't need to be nearly as pure as jet fuel so the processing costs would be lower).
But really, 125 kiloliters per year? Unless someone misplaced a decimal point, that's basically one 777 fuel load per year. Talk about your drop in the bucket...
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Old 15th Apr 2019, 12:56
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Kilo Watt hours of course, normally on batteries amp hours are used because of discharge voltage curves but on EVs the traction battery is always measured in kilo Watt hours as the battery management controller takes care of any voltage changes.to keep power delivery constant.

Lithium, Australia is the biggest supplier is a low density metal, it is the cobalt that is in short supply and nickel is very dirty to refine, but other chemistries are being investigated. Sodium ion, Zinc air and Aluminium air which is quiet good but not rechargeable would be an anode change and liquid removal to recharge. So I think hybrids and short range electrics will creep in then in 10 to 20 years electric full range aircraft will start appearing. So as with mobile phones it will take time to be main stream.
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Old 15th Apr 2019, 23:03
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Originally Posted by Longtimer
"OSM Aviation Group CEO Espen Høiby....goal to shift all short-haul routes to electric flight by 2040..."
There is no question that some useful short distance hops are possible in electrically-powered general aviation aircraft. Work is ongoing in human-carrying drones. Advances in high-power brushless DC motors, lithium polymer batteries, precision GPS and solid state inertial platforms make this possible.

However there is a huge difference between that and the air transport category. Most aviation energy is not consumed by general aviation or business aviation -- it is by commercial air transport. I don't know the exact numbers but I'd estimate over 90%, maybe over 95% is by commercial air transport, ie airline and cargo operations. Therefore any meaningful electric aviation solution must include that or at least articulate a plausible path using attainable technology to achieve electrically-powered commercial air transport.

The quote mentioned "short haul routes". To my knowledge this is routes under 3 hr, although some authorities use 3,200 km (1,727 nm).

What would be the energy or battery requirement for airline transport operations over (say) 1,500 km? Ideally this should provide roughly similar payload and travel time performance, else all of society is plunged back to the pre-jet era. Electric-driven jets are not really possible but electric-driven propellers are. Propeller-driven airliners with near jet performance have existed: the Tu-114 (based on the Tu-95). Fortunately its engines are rated in shaft horsepower which avoids the tricky conversion of pounds thrust to horsepower. https://en.wikipedia.org/wiki/Tupolev_Tu-114

The Tu-114 had 4 x 14,800 hp engines. If we assume cruise power at 77% or 45,584 hp, that is 33.9 megawatts. A short-haul flight of two hours would therefore require roughly 67.8 megawatt-hours. How much battery power would be required to fulfill that?

33.9 MW is engine output, not including gearbox and propeller efficiency. To provide this electrically we must consider battery efficiency (say 90%) and electric motor efficiency (say 90%) for overall efficiency of 81%. We won't consider efficiency losses from motor controllers or other sources. This means the batteries must hold about 83.66 megawatt hours (not including reserves) for a two hr "short haul" flight of about 1,500 km.

The battery pack on an 85 KWhr Tesla Model S weighs about 540 kg (1,200 lb). We would need about 984 of these which would weigh about 1.18 million pounds. The Tu-114 had a payload of about 55,000 lb, but 130,000 lb of fuel for a total payload of 185,000 lb.

So very roughly, we only need an improvement in battery energy/weight ratio of about 10x to make this feasible. To recharge 10 of these after landing would require an on-site dedicated two gigawatt power plant, and the assumption each aircraft can sustain an approx 100-200 megawatt charge rate. Maybe Boeing's experience with the 787 li-ion batteries would give them an advantage.
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Old 15th Apr 2019, 23:30
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Just a completely random thought about the physics of electric, aircraft, isn't the consumption of the weight of fuel and the jettisoning of the depletion products overboard actually the thing that makes any extended flight possible for realistic commercial transport? Batteries don't lose significant weight as they are depleted. In a nutshell, in the current extended range comes from the continuous reduction in weight and thus consumption energy per nm is continuously reducing as the flight proceeds. I don't see how batteries can do this without physically jettisoning them.
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Old 16th Apr 2019, 11:44
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Originally Posted by joema
There is no question that some useful short distance hops are possible in electrically-powered general aviation aircraft. Work is ongoing in human-carrying drones. Advances in high-power brushless DC motors, lithium polymer batteries, precision GPS and solid state inertial platforms make this possible.

However there is a huge difference between that and the air transport category. Most aviation energy is not consumed by general aviation or business aviation -- it is by commercial air transport. I don't know the exact numbers but I'd estimate over 90%, maybe over 95% is by commercial air transport, ie airline and cargo operations. Therefore any meaningful electric aviation solution must include that or at least articulate a plausible path using attainable technology to achieve electrically-powered commercial air transport.

The quote mentioned "short haul routes". To my knowledge this is routes under 3 hr, although some authorities use 3,200 km (1,727 nm).

What would be the energy or battery requirement for airline transport operations over (say) 1,500 km? Ideally this should provide roughly similar payload and travel time performance, else all of society is plunged back to the pre-jet era. Electric-driven jets are not really possible but electric-driven propellers are. Propeller-driven airliners with near jet performance have existed: the Tu-114 (based on the Tu-95). Fortunately its engines are rated in shaft horsepower which avoids the tricky conversion of pounds thrust to horsepower. https://en.wikipedia.org/wiki/Tupolev_Tu-114

The Tu-114 had 4 x 14,800 hp engines. If we assume cruise power at 77% or 45,584 hp, that is 33.9 megawatts. A short-haul flight of two hours would therefore require roughly 67.8 megawatt-hours. How much battery power would be required to fulfill that?

33.9 MW is engine output, not including gearbox and propeller efficiency. To provide this electrically we must consider battery efficiency (say 90%) and electric motor efficiency (say 90%) for overall efficiency of 81%. We won't consider efficiency losses from motor controllers or other sources. This means the batteries must hold about 83.66 megawatt hours (not including reserves) for a two hr "short haul" flight of about 1,500 km.

The battery pack on an 85 KWhr Tesla Model S weighs about 540 kg (1,200 lb). We would need about 984 of these which would weigh about 1.18 million pounds. The Tu-114 had a payload of about 55,000 lb, but 130,000 lb of fuel for a total payload of 185,000 lb.

So very roughly, we only need an improvement in battery energy/weight ratio of about 10x to make this feasible. To recharge 10 of these after landing would require an on-site dedicated two gigawatt power plant, and the assumption each aircraft can sustain an approx 100-200 megawatt charge rate. Maybe Boeing's experience with the 787 li-ion batteries would give them an advantage.

I'd thought cruise thrust was usually only about 25% of takeoff power, suggesting the requirements are correspondingly more modest.
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Old 16th Apr 2019, 15:45
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Originally Posted by etudiant
I'd thought cruise thrust was usually only about 25% of takeoff power, suggesting the requirements are correspondingly more modest.
I think for turboprops it's typical to cruise at 70-80% torque. Since many turboprop engines are thermodynamically flat-rated, the actual energy consumption to maintain cruise torque can still be quite significant -- certainly more than 25%.

A large electric-powered propeller-driven air transport vehicle with Tu-114-level payload and performance would have to expend about the same energy. It appears that would equate to over 30 megawatts sustained cruise output for a two-hour short-haul flight, or over 60 megawatt hours, not counting reserves or takeoff.

It's true that batteries don't get lighter as they discharge, so expended units could hypothetically be progressively jettisoned in flight. That would help but would require a large new infrastructure. At current energy densities that would equate to over 1 million lb of batteries per plane, so it's not really possible with current technology. It would require at least a 10x improvement in battery energy/mass ratio just to achieve short-haul capability for something the size of a prop or fan-powered 737. To recharge the planes, each airport would require one or more on-site dedicated multi-gigawatt power plants.

You could pick up a little more efficiency using unducted fans, but that's just nibbling at the edges of a much larger problem.
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Old 16th Apr 2019, 15:54
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CurtainTwitcher
Just a completely random thought about the physics of electric, aircraft, isn't the consumption of the weight of fuel and the jettisoning of the depletion products overboard actually the thing that makes any extended flight possible for realistic commercial transport? Batteries don't lose significant weight as they are depleted. In a nutshell, in the current extended range comes from the continuous reduction in weight and thus consumption energy per nm is continuously reducing as the flight proceeds. I don't see how batteries can do this without physically jettisoning them.
There is a battery technology that might let you do this. The flow battery: https://en.wikipedia.org/wiki/Flow_battery They are normally used for things like balancing wind power on the electricity grid because they can be scaled up to arbitrarily large sizes - all you need is a bigger tank of electrolyte.

The other nice thing about them is that you can separate the process of recharging from the battery itself - rather than running it in reverse to recharge, you can fill it up with fresh electrolyte drawn from some off-stage industrial process.

Now, if the electrolyte was the sort of stuff you could happily release into the air once spent, and also the sort of stuff you could manufacture regeneratively...well, you could use the rest of the world as the other half of the battery. This is probably not going to happen outside science fiction, though, as one of the best chemistries for a flow battery involves bromine. Although there are enormous reserves of it in the sea, it's extremely ozone-destroying (especially if you were thinking of releasing it in the stratosphere!) and quite toxic.

In any case, using the Tu-114 example above you'd need ~60 tonnes of lithium bromate and hydrogen for that 2 hour trip. If you screw your eyes up right, you could make a case the Br would end up back in the sea and consequently be renewable, but the Li would need to be mined and we're going to want every tonne for batteries of all kinds where it would also be recyclable.

There are organic flow batteries but going by the same rough calculation for the best quoted electrolyte, the Tu-114 example would need about 200 tonnes of the stuff and it's usually synthesised from...oil.
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Old 16th Apr 2019, 17:27
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A good point that an electric will not decrease in weight in flight, so will consume more energy for the same flight, also the under carriage will have to be stronger to take the higher landing weight.

So may be the best way to work out kilo Watts needed is measure the first hour of cruise fuel consumption, convert to kilograms used ;
then taking the engine efficiency/100 x kg used x kW per kilograms of fuel = kilowatt hours used per hour.

So example 30%/100 x 100kg x 12kW = approx. 400kWhrs best battery at the moment 0.5 Kg/kWhr so 800Kg for one hour of flight..

But a battery at 3kWhr per Kilogram would be close at 133kilograms just multiply flight duration for total weight. I may have over estimated the engine efficiency, if lower then it would be a closer to liquid fuel.

The hope is the Lithium air battery will come closer to this power density, but of course would still need the oxygen from the air to function.
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Old 17th Apr 2019, 19:42
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Originally Posted by Wizofoz
….Except the e-flyer exists and has flown- the amphibian is just one more "paper aeroplane",
There is a video on their website of it flying News So little more than a paper aeroplane.

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Old 17th Apr 2019, 22:21
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Originally Posted by horizon flyer
There is a video on their website of it flying News So little more than a paper aeroplane.
See post #32.
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Old 22nd Apr 2019, 14:33
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Another Engine in the works.
  • 22 April, 2019
  • SOURCE: FlightGlobal.com
  • BY: Jon Hemmerdinger
  • Boston
Electric motor company MagniX will supply powerplants for Eviation Aircraft’s in-development electric aircraft Alice, marking another win for the upstart motor maker and a second power option for Alice buyers.

Eviation will offer the nine-passenger Alice with triple MagniX Magni250s – electric motors generating 375shp (280kW). They will turn Alice’s props at 1,900rpm, says MagniX chief executive Roei Ganzarski.

“They are very light and very powerful,” he says of the Magni250 propulsion system.

Eviation expects the Alice, a commuter and business aircraft, will be certified in 2021 and enter service in 2022.

MagniX, based in Redmond, Washington also expects 2021 certification for the Magni250.

Israel-based Eviation had already named Siemens as one motor supplier for the Alice. Siemens’ system includes 260kW electric motors powered by a 900kWh lithium-ion battery pack. That same battery pack will power the Magni250s.

Two motor choices eases "potential supply chain issues”, giving customers “broader choice of price points and maintenance schedules,” Eviation chief executive Omer Bar-Yohay has said.

The Alice will have three pusher propellers – one behind its “V” tail and one each at the wingtips – and be capable of flying 565nm (1,050km) and at 260kt (482km/h), says Eviation.

That range would enable the Alice to serve many existing air routes and make new connections via smaller, under-served airports, the companies say.

“That’s a significant aircraft,” Ganzarski says of the Alice, noting 45% of air routes fall within its range.

Actually, 55% of airline flights worldwide in April were within 565nm, according to Cirium data and analytics.



=rightEviation Aircraft

Each Magni250 contains two modules (managed by separate inverters) that, combined, provide 375shp. If an motor problem occurs, software can shut down one module and keep the other running, meaning the system will still provide 50% power, a feature Ganzarski calls "graceful degradation".

“You can really create a high level of redundancy,” he says.

MagniX has conducted more than 1,500h of motor ground tests in both Redmond and at its Australia site, and Eviation has been testing a Magni250 with the Alice’s propellers in Israel, says Ganzarski.

Eviation says MagniX is one of few manufacturers capable of building an electric engine for the Alice.

“MagniX has not just tested their propulsion system, but they’ve ran it with Alice’s specific profile,” Eviation says. “We can reassure customers that their motor can perform as expected under normal conditions and extreme ones.”

Eviation, which is providing the battery system, has been assembling the first Alice prototype in Vannes, France. Alice will have a fly-by-wire system and Honeywell cockpit avionics.

“We hope to fly the aircraft ahead of the Paris air show in June, where it will make its debut,” Bar-Yohay has said. MagniX’s motor will also be on display at the show.

Eviation plans to achieve first flight of the fly-by-wire equipped Alice this fall. It will perform flight testing in Prescott, Arizona, and expects three aircraft will join the flight-test campaign, including two prototypes and one production-conforming aircraft.

THE CASE FOR ELECTRIC

Owned 100% by Singapore investment company Clermont Group, MagniX is also developing its 751shp Magni500 motor for installation on de Havilland DHC-2 Beaver seaplanes operated by Canadian regional carrier Harbour Air.

Those motors well suit Harbour because many of its flights have duration of only 30min – within the system’s capability.

Despite naysayers, Ganzarski insists technology already allows for development of electric passenger aircraft, though not anything like a widebody jetliner.

There’s no escaping that the best lithium-ion batteries have about 260Wh/kg of energy density – almost 50 times less than jet fuel’s 11.9kWh/kg density.

Electric aircraft therefore cannot nearly match the range of fuel-powered aircraft.

However, small electric passenger aircraft can efficiently operate countless shorter-distance routes, Ganzarski says.

The key is developing aircraft from scratch around batteries and motors, making them essentially “flying batteries”, says Ganzarski.

Electric motors are lighter and smaller than fuel engines, and they can be fitted on an aircraft’s wingtips, such as on the Alice.

“If I tell you that tomorrow we can take nine passengers 650 miles, and maybe in five years [take] 50 people 650 miles, that’s a reality,” Ganzarski says. “I see no reason you cannot… with the current motor technology we have.”

Electric motors cost significantly less to operate than fuel-burning engines – 60-80% less than internal combustion engines, says Ganzarski.

The electricity required to power a small electric aircraft on a 100-mile flight might cost $8, compared to $350-$400 for the fuel a convention aircraft would need, he says.

Also, electric motors also have far fewer parts than fuel-burning engines, meaning they require significantly less maintenance and overhauls.
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Old 22nd Apr 2019, 15:19
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Wow, that's a shiny hangar floor!

As a person who flies and certifies aircraft, I would be concerned about a wing or tail low landing causing propeller damage. In any case, I expect that a computer in the plane would have to reduce thrust on a wingtip motor, in the case of a loss of thrust on the other side for any reason. They could be cross shafted like a tilt rotor, but that gets complex and heavy. The V tail would be challenged providing enough yaw control to overcome thrust asymmetry for the wing motors.

And, I imagine a really inconvenient hump in the cockpit floor where the nosewheel has to be when it is retracted.

I was keenly interested in the innovation of the Learfan, back in the day. But after understanding the many interrelated design innovations and challenges, it became apparent that it is less than ideal to innovate a very different airframe design, a different powerplant, and different propeller arrangements all on one airplane at one time. I'm very much in favour of electric aircraft development, and participated in a design study, but that was for re [motoring] a 172. Everything about the airframe and propeller (to have been MTV electric) was proven, and very accepted, it was only the changed powerplant which was open for investigation and development.

I continue to watch with interest, though with the eye of an aircraft certifier.....
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Old 22nd Apr 2019, 15:31
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I think Harbour Air's electric Beaver is the real deal. The numbers can be made to work for the 20 minute scenic flights they do all summer and the Vancouver - Nanaimo sched ( 32nm), assuming a 1 hr turn time for a fast recharger at the dock at Vancouver and Nanaimo. One advantage is that conventional airplane parts are stupid expensive ( eg 50,000 USD for an overhauled Beaver engine good for 1600 hrs) so expensive bleeding edge technology can still be cost effective.

The bigger challenge is that so far battery technology has increased incrementally. To make electric power viable for more than specialty niche applications like what Harbour air wants to do, you need batteries 10 times more power per kg than what is presently available and there is nothing like that on the horizon.
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Old 22nd Apr 2019, 15:47
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And in addition to the weight of the batteries, there is also the recharge time. Unless they can accept a lot of juice really quickly, the economics of short-haul operations will be substantially compromised.
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Old 22nd Apr 2019, 15:53
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Originally Posted by Pilot DAR
Wow, that's a shiny hangar floor!
That's a computer-generated artist's concept image.

As a person who flies and certifies aircraft, I would be concerned about a wing or tail low landing causing propeller damage. In any case, I expect that a computer in the plane would have to reduce thrust on a wingtip motor, in the case of a loss of thrust on the other side for any reason. They could be cross shafted like a tilt rotor, but that gets complex and heavy. The V tail would be challenged providing enough yaw control to overcome thrust asymmetry for the wing motors.
With any EV or E-anything.... believe it when you can buy one. The hype-to-reality ratio in this area is about 50:1.
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Old 22nd Apr 2019, 20:38
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Aeroplanes now! Well I did have one with a supercap that could carry its own weight happily around for nearly 3 minutes.....

The energy density of hydrocarbon fuels is 20-50 times higher than the most advanced Li-ion concept based electrochemical batteries.
Wake me up when it's 2-5x higher, and the battery's brisance a fair bit less than good 'ol black-powder.

Ye'd do better to use the piddling amount of very expensive renewable energy that we produce to synthesize a better grade of avtur.

And if you sit down and think about the chemistry, engineering and economics carefully enough, is the truth of the matter.

Mac

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