How Far Away Is Commercial Electric Aviation?

NOV 11 2014 BY MARK HOVIS 52

Commercial electric aviation – what a mouth full.  How far away is it anyway?

First, we need to look at a portion of electric flight to help determine where are we and where are we going. I am an avid EV enthusiast, yet initially I had written electric flight off as impractical. That was until inventors/engineers one by one started breaking the barriers. In no particular order since most of these electric aviation milestones have happened rapidly over the past 20 months.

Solar Impulse 2

Solar Impulse 2

Perpetual Aviation

InsideEVs covered the story on the Impulse 2, a massive solar plane outfitted with 17,248 solar panels capable of capturing enough daytime energy to remain in flight all night making this two seater craft capable of perpetual flight like the unmanned Airbus Zephyr 7 which marked an 11 day flight found here .

The 72 meter Impulse 2 is outfitted with four 17.5 HP electric motors for a total 50 kW output propelling this craft along at 90km/h (56 mph).

These and other large wing solar planes open the door to many applications. Some are manned and others are drone applications previously unattainable without refueling.

 

Attainable Electric Aviation- Now

Airbus Group’s E-Fan

Airbus Group’s E-Fan

In March 2014, Airbus Groups E-Fan successfully completes its first public test flight.

The E-Fan weighs in at 600 kg (1322 lbs) and is outfitted with 120 lithium polymer cells rated at 40 Ah per cell. The total engine power is  60kW capable of providing 110 km/h (68 mph) take off speed, 160 km/h (100 mph) cruise speed and 220 km/h (124 mph) max speed.

The E-Fan has a flight endurance of 45 min – one hour. Applications lend itself to training flights and aircraft rentals including towing applications for gliders. Future E-Fan models are looking at four seats and will be equipped with  range extenders thus allowing full electric takeoffs and landings with cruise altitudes provided by a larger APU. In July 2014, the all electric Sun Flyer Electra One made it’s maiden flight.   

Charlie Johnson, AEAC’s President and Chief Operating Officer stated: “Our primary focus will be flight schools with a high utilization rates and aircraft rental operations. We believe the lower operating costs, along with the simplification of the frequent maintenance checks required by the FAA for training operators, will result in significantly lower overall costs for Sun Flyer.” The price expected is below $180,000 with one year payback compared to the ICE version.

Sun Flyer Electra One

Sun Flyer Electra One

Breaking Records

Long-ESA Electric Plane

Long-ESA Electric Plane

The attached video really tells the tale best, but here is the short version. There are those like Chip Yates and Elon Musk who like to dance at the other end of the rainbow where risks including speed, power, and innovation take EVs beyond current comprehension.  After breaking 18 world records, including 10 for world’s fastest electric motorcycle, Chip Yates added the latest five for electric aviation:

  •  Altitude (14,701 ft.)
  • Speed over a 3 km course (201 mph – 4 pass avg speed)
  • Time to climb to a height of 3,000 m (5 min 32 sec) – selected by the NAA as the “Most Memorable Aviation Record of 2013”
  • Altitude in horizontal flight (14,564 ft)
  • Speed over a 15 km course (140 mph (2 pass avg speed)

Next up for Chip Yates- Transatlantic Electric Flight

Commercial Electric Aviation

Boeing SUGAR Volt Hybrid Electric Plane

Boeing SUGAR Volt Hybrid Electric Plane

Anyone starting their comprehension of commercial electric air travel at this point would probably dismiss this notion. One of the paradigms that people get stuck in is thinking “all” areas of a market must be accomplished before a product is viable.

The twenty and soon to be thirty available electric automobiles is proving that a growing number understand otherwise. In my travels, I have made many commercial flights under thirty minutes. My favorite was flying from Cleveland Oh to Cincinnati OH. From the flight deck: “The aircraft has now reached cruising altitude.” Minutes later. “The flight is now clear for decent.”

Such commercial flights could certainly be grounds for the first commercial electric flights. Other hybrid applications include cities that will require takeoff and landing under electric power then transferring to traditional or biofuels that could also use substantially less fuels like the hybrid electric Boeing SUGAR Volt (Subsonic Ultra Green Aircraft Research) or the EADS Rolls Royce powered E-Thrust (report here).

Rolls Royce powered E-Thrust

Rolls Royce powered E-Thrust

The E-Thrust concept is similar to the turboelectric distributed propulsion (TeDP) work under way at NASA. The EADS IW concept uses a single large turbine engine to generate electricity to power six ducted fans that provide thrust. This allows propulsive and thermal efficiency to be optimized separately. The turbine engine can be optimized for thermal efficiency (turning fuel into shaft power) while the ducted fans increase effective bypass ratio and therefore propulsion efficient (turning shaft power into thrust).


The technological barrier that must be overcome for transcontinental flight is the energy density of batteries. Energy density measures how much power can be generated vs weight of the battery.

airbus shock test

EADS VoltAir Concept

Tesla CEO Elon Musk states that once batteries are capable of producing 400 Watt-hours per kilogram, with a ratio of power cell to overall mass of between 0.7-0.8, then an electrical transcontinental aircraft becomes “compelling”.

Looking Forward

But there is clearly an electric aviation market prior to transcontinental flight as described above.

Like the automotive sector, it will come in various forms from  hybrid applications like the Boeing SUGAR Volt to the pure electric EADS concept VoltAir (report). Such a forward thinking design with ultra-high density electric engines and less conventional rudders, elevators and the like would certainly change the face of todays methods. Anything of this magnitude in aviation will take 20 -40 years to materialize, but it is exciting to see large companies like Airbus and Boeing that are quite a bit past just having the conversation.

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52 Comments on "How Far Away Is Commercial Electric Aviation?"

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Brian

“Other hybrid applications include cities that will require takeoff and landing under electric power then transferring to traditional or biofuels”

This is an interesting thought. It is similar to the European trend of eliminating emissions within the city centers. This certainly helps lower air pollution where people live.

Conversely, aren’t emissions in the higher strata of the atmosphere far worse in terms of global climate change effects? From this perspective, it might actually make sense to burn the fuel during takeoff and climbing (i.e. highest demand) and use electricity to maintain cruising speed.

Either way, the point is that even plug-in hybrid aircraft can have an impact.

CounterStrike Cat

A lot of ground emissions can be saved without changing anything at the planes, just stop stupid 30+ minutes waiting times with stop and go on the taxiway with running engines before they actually reach their start position…

Mint

Those “running engines” aren’t using much fuel on the ground. Maybe a couple percent of overall fuel use at most.

Rob

it’s still unnecessary pollution though

Cavaron

As far as I know, most people close to airports complain about the noises. Don’t know how much an (hybrid)electric plane can help with that. Is the noise reduction comparable to the car sector (thinking about large passenger planes).

Brian

I live about a mile away from SYR, so I am very familiar with that problem. During the summer, when my windows are often open at night, we hear hours worth of airplanes idling on the runway. The idea of electric taxiing is a no brainer, and should have been implemented 10 years ago. This is a far worse offender in terms of noise pollution than the actual takeoff (which lasts only a few seconds).

Rob

noise IS the biggest complaint, but I have also read about the smell of aviation fuel and what happens to washing when hung outside on the line

K-lein

Actually commercial aviation has documented cooling effect on the atmosphere.
This is due to the condensation trails (water released by burning of fuel in jet engines turning condensing into clouds) reflecting a significant amount of sun light into space without allowing it to heat up the atmosphere or the ground.

This was suspected for a long time but there was no way to prove it (you have to stop all aircraft from flying)
It was eventually proven on September 11th 2001 when the US airspace became a no-fly zone for 3 days.

Chris

Brian this is being developed right now, with electric motors placed in main gear hubs powered by the aircrafts APU. Engines would only be started just prior to takeoff saving fuel and CO2 emissions. I work in aviation and it just boils down to a math problem of the value of the fuel savings versus the cost of installation and the fuel burn in flight to carry the extra weight of the electric motors over the planned life of the aircraft.

Brian

I understand that cost is king in aviation. We see the airline industry go through a continuum of burst/bust cycles. How many times can one industry go bankrupt?

At the same time, the external costs of air travel are perhaps even larger than those of ICE cars. Between pollution in the upper atmosphere and the horrible noise pollution for areas surrounding busy airports, I wish that the industry would take more aggressive steps to be good citizens.

gsned57

There are a lot of engineers at the big Aerospace companies (I am one) who are very interested in Electric flight both manned and unmanned. There is a lot of $$$ being spent in this space and I agree with Elon that as the batteries improve so does the capability. It’ll be a fun transition to watch and be a part of.

Lad

The goal should be to not burn hydrocarbons in the upper atmosphere to eliminate smog and greenhouse gasses.

How about this: Generate hydrogen from solar cells for use in a hybrid airplane that generates electricity from an onboard fuel cell. The aircraft would be powered by electric motors and carry buffer batteries. The key is still, as it always has been, “The Better Battery.”

Brian

If I understand your comment correctly, it sounds like you are proposing generating hydrogen mid-flight from solar panels. This doesn’t make any sense. It is far more efficient to use the electricity directly. If there is excess, store it in a small battery bank.

Brian

Re-reading your comment, I may have interpreted it wrong. There is merit to an airplane running on a fuel cell. Where the hydrogen actually comes from is a secondary question.

By extension, heavy-hauling ground transport (e.g. Tractor Trailers) are also an application where fuel cells may reign supreme. I just don’t think they are a good idea for light ground transport, but that doesn’t mean there is no place for them.

mrenergyczar

Toyota is working on the hydrogen plane….

Craig

….even though nobody asked them to.

Steven

It’s funny, no one’s knocking their door down to do it.

Anthony Fiti
Oddly enough, I was thinking about this last weekend. A 737 has a fuel capacity of 26,200 L of fuel. Using space-filling solid state batteries, thats roughly 29MWh using the 1,100Wh/L figure from Sakti3 from a recent Autoline epsiode (http://www.youtube.com/watch?v=Wc3nzup5XuM). A 787 would have a capacity of around 125MWh, and a 777 would have a capacity of 200MWh. So the only thing I couldn’t figure out is how much energy would a 737 use on a 2,500 mile flight? Could a plane that size get across the country on 29 MWh of energy? Would it have to fly at slower speeds using a scaled up version of an E-Fan? My best math was able to get me to about two 6MW engines (peak consumption) producing 150kN of thrust each. The problem is that batteries don’t burn off the way fuel does – so the take off weight is the same as the landing weight. So the plane would use 12MW for the first hour or so of flight to get to cruise altitude, but from there on it would use about 7MW each hour thereafter. It only ends up around 3 hours of flight (factoring in FAR 121 minimums). At… Read more »
Blueberry Blipblop

In the case of aircrafts I would say Wh/kg is the restricting factor, rather than Wh/dm3. So your numbers would have to be divided by 5 or something like that (assuming 5 kg/dm3).

Mint

I got somewhat similar numbers to you from a different angle.

Musk is assuming that you have 70% battery weight, and 29MWh @ 400Wh/kg would be 72 tonnes. So lets say the plane weights 100 tonnes. In the end these figures will be the same no matter what mass we choose.

If we optimistically assume a glide ratio of 20:1, that means it needs roughly 78MJ/mile. At 560mph, that’s the same 12MW figure you came up with.

But I think E-fans won’t be as efficiency as a motor on a road, so maybe 80% efficiency is the best you could hope for. That results in ~1100 miles range.

I can only guess that Musk is talking about a revolutionary design (he mentioned no tail/rudder) with higher lift-to-drag ratio.

Dr. Kenneth Noisewater

What’s the mass of those batteries? Mass counts a lot more for planes than for cars.

Lensman
That seems to match what I figured with a back-of-the-envelope calculation a few years back, after reading an article on the SUGAR Volt hybrid aircraft. I think Musk is much too optimistic about coast-to-coast flights. Another point is that the idea of a hybrid aircraft is to use fuel where high power is demanded… which is during takeoff, landing, and climbing to cruising altitude. At cruising altitude, the electric motors can be used to maintain speed and altitude. So the idea of using electric power inside city limits, when taking off and landing, seems to be unrealistic in regard to a hybrid plane. Now, that’s not to say there is no room for a relatively small, short-range “puddle jumper” electric commercial plane. But I do wonder about the battery recharge time. Will that only be practical with battery pack swapping, or for planes which only fly occasionally, with several hours between flights? The latter restriction would make them unattractive to most airlines. For longer flights, I wonder about the cruising speed. Commercial jets travel at about 90% of Mach 1 (the speed of sound). Generally speaking, prop-driven planes don’t fly that fast, because the props lose efficiency when the plane… Read more »
Manabu

Musk is imagining a vertical take-off and landing, electric, supersonic jet. So, probably, not propeller driven.

The first time I heard I thought it would use something like beamed microwave space solar power or something instead of tons of batteries.

Spec9

I’m skeptical on this. The energy density just isn’t there. Biofuels is probably the way to handle aviation.

Rick Danger

Nice article Mark, thank you!

Assaf

+1, thanks Mark for a great article!

Sounds like with some luck, we might see short-haul commercial aviation (small-medium planes) in less than 2 decades?

Also, you put Chip Yates in there but didn’t really discussed light aviation. How far are planes like Yates’ from becoming such a ‘killer app’ in light aviation, so as to render ICE planes hopelessly outmatched for general light-aviation needs? Or is that too optimistic?

Lensman

Even general light aviation needs planes which can fly for hours at cruising speed. Battery powered planes simply are not gonna cut it. Musk is much too optimistic; I figure we’d need an energy density about five times current values to have a plane which can fly for more than half an hour or so.

Now, I do agree with the article’s point that there could be a niche market for short-range planes. But the tech simply isn’t there to knock ICE planes out of the market. Planes are much more weight-sensitive than cars are.

I think planes and helicopters will be the last holdout of the ICEngine, for various reasons. We’ll need much smaller, much lighter batteries to make electric planes practical than we need for electric cars… an that’s even assuming the problem with limited speed of prop-driven planes is overcome.

We can imagine some far future tech with superconductor-enabled magnetohydrodynamic (MHD) engines powered by ultra-small batteries. So perhaps our grandchildren will fly in planes which need no fuel. But that’s using tech that’s not even on the drawing board.

Bennyd

Thanks for posting an article with real substance…getting tired of too much 0 to 60 hype…

Scott Franco

For light aviation, EVs are a possibility, but a 1 hour flight time is a non-starter for most applications. It takes 10-15 minutes of run time to get into and out of an airport pattern, leaving little time to tool around. At 2 hours a much more practical aircraft is possible for light use aircraft. A LSA or light sport aircraft that goes for 2 hours would definitely sell.

Aircraft have radically different needs than cars. A car can be heavy, but in an aircraft the range is greatly affected by the weight. An aircraft is using power to displace its weight constantly. This implies that concentrating on battery weight over capacity will help, and it is why LiPo (lithium/polymer) batteries rule model aircraft right now.

FSJ

Training sorties are around an hour. I have done it hundreds of times. So EV airplanes would work fine for training today. It’s not a non-starter for this application.

George Bower

Good discussion.
I can’t get to the Voltair pdf for some reason.

Gene Frenkle

How about using the Phinergy battery in a turboprop like the Saab 2000? The 60 seat plane could travel around 400 mph and travel 500 miles, so it would function as the spoke in our hub and spoke commercial system. If the Phinergy battery is real and they can improve the efficiency it might be cheaper than kerosene.

Priusmaniac
As a hobby I spend some time at finding ways to make a rocket at least partially electric. It took a while to break the Elon dogma that rocket can’t be electric but I finally found a way to at least do it partially. It takes the form of a stage bellow the first stage. A big battery of cylindric shape with 8 electrofans attached to it. Large GE 90 sized electrofans. At time zero the rocket engines don’t go on but the electrofans get powered by connected wires until they are at high rotation speed and full trust. Then take-off happens. The wires are disconnected and the power now comes from the 100 ton battery. The entire rocket rises to 20000 m of altitude and 600 mph speed. At that point the electric stage separate and the rocket first stage ignite. It is then at a high altitude and at 600 mph speed instead of at sea level and zero mph. This result in a further speed increase of the rocket taking place with a lower dynamic drag due to the higher initial altitude. The 600 mph start speed also give an extra. The electric stage is straight made… Read more »
Scott Franco

Acutally, electric rockets are an old concept in use for quite some time:

http://en.wikipedia.org/wiki/List_of_spacecraft_with_electric_propulsion

Lensman

Ion drive and plasma drive may work in deep space, where a tiny but constant thrust is better in the long run than a few minutes’ thrust from an ordinary rocket. But they are useless for an airplane or a rocket lifting off from the ground; the thrust is much too low.

Priusmaniac
Right, ion drive is good for low force in space drive. For a launch rocket, apart from the extra stage described, if you really want an electric rocket you need something way more dramatic then a low energy ion thruster. In fact there are two distinct problems, you need an ejection mass to act upon to get the resulting reaction force and you need energy to push that reaction mass away as fast as possible. A standard rocket uses the reaction mass as the source of energy as well. An electric rocket equivalent would be a rocket that would violently expel a plethora of 18650 batteries that would in the same time provide the energy to do so. Of course in a practical way you wouldn’t want to throw away some thing as expensive as 18650 cells, so you rather expel something else. An example would be to expel rail gun rounds the one after the other. You would indeed get the reaction force and throw away something that is not too expensive. By the way, it would be possible to obtain velocities that are higher than what is possible trough chemical reactions as demonstrated by military artillery tests. So… Read more »
Lensman

Yeah. I don’t think the scenario described in the comment upstream, a battery-powered booster stage for a rocket, is workable. Not for anything larger than a toy rocket. Batteries are much too heavy to power a propeller-driven rocket booster stage. You’d have more luck using something like SpaceShipOne’s (and SpaceShipTwo’s) carrier plane “mother ship”. That carrier plane would be a better candidate for electric propulsion, where most of the lifting power is provided by wings, rather than sheer force of propeller power.

Priusmaniac
Yes an electric space ship one mother ship could also be an option but there are two problems with that scenario. One, you have to supply power for longer since your climb time is longer (much more than 60 seconds) and not less energy since your equivalent mother ship would be huge. Two, you need to completely change the Falcon 9 configuration to allow it to be carried horizontally under the mother ship and you could also have to add wings mass to the rocket like for a Pegasus rocket. The electric fan (not propeller) configuration allows to maintain the original Falcon 9 vertical position. In more you don’t need a runway for it and as an extra advantage you clear the ground of the intense heat associated with a ground rocket start. The 8 GE sized E-fans would blow massive amounts of air but that would still be cold air so there would be no need for a special starting place. Of course you could also look at using almost standard GE90 turbofans instead of E-fans but then you are back at oil again. On the other end that would also be interesting because a GE90 is using atmospheric… Read more »
kdawg

There’s some electric helicopters too.

Jouni Valkonen

Electric aviation could be feasible if batteries are resilient enough and they can be charged fast enough. Musk’s estimation of 400 Wh/kg could make sense and be good enough energy density.

The idea how electric airplanes could make sense is that they can fly at much higher altitude, because they are not depended on atmospheric oxygen and also the heating of intake air due to friction does not reduce the efficiency of electric jet engine. This is curious that with commercial electric jets we must go for hypersonic mach 6 flight, because otherwice the energy that can be stored into batteries is not sufficient!

Also high landing weight is not a problem, because vertical landing is possibly feasible and when airplane is descending from 50 000 meter cruising altitude, fans can regenerate electricity and charge enough juice to batteries that allows soft powered landing.

Priusmaniac

It is relatively easy to make an electrofan that can replace a conventional turbofan on a subsonic airplane, but it is way more difficult to make an electric system that would be able to go supersonic. That is also something I try to find but it is very hard. Up to now one of the only ways is to have a reactor composed of an electrofan followed by electric compressor stages and then an electric arc to heat the air as a replacement for the kerosene. The turbine would not be necessary since the compressor stages are moved by an electric motor. The top speed can be even higher than with a standard reactor because the arc can heat the gas much higher than kerosene can but the system takes huge amounts of electricity. In a way you would have to make some kind of hybrid where that electric reactor would be fed by a large on board APU.
That is all weighing a lot so the take-off might be a problem. Supersonic electric is therefore a very serious challenge but as a hobby I like to brainstorm on it.

K-lein

Since you power the compressor/fan directly out of the battery, why waste precious energy heating up the air (except maybe for de-icing when needed)

Priusmaniac

The air needs extra energy to allow supersonic speed. If you take it in, compress it and just release it at the back again, you can never get to supersonic speed. The ejection speed is just too low without the heat jolt. Compressing further could heat as well but then you either limit the incoming flow to much or get into to high pressures and associated mechanical stresses.
In the past heating was examined with a nuclear reactor and that was indeed working but that is not an electric plane anymore but a nuclear one.
For an electric plane you can use an electric arc, a resistor, electromagnetic systems, perhaps microwaves, but you need to have something that transfers extra energy to the flow to go supersonic.

Jouni Valkonen

+1

good arguments. However I disagree. I do not think that heating is required because intake air heats into very high temperatures in the compression process itself and due to friction of high hypersonic velocity. At mach 6 cruising velocity, temperatures in the compressors are already approaching what the materials can take due to friction. Therefore we probably cannot go faster than mach 6 without using rocket engines.

And if you think lower cruising speeds, then heating is just more efficient if it is used to inject kerosene into combustion chamber. But I guess this solution will have worse fuel economy than Black Bird. Not good equation if we go with batteries!

Priusmaniac

There sure is a lot of heating taking place in a supersonic compressor stage, even more so for hypersonic, but I doubt that would be enough to have net positive trust at supersonic speed, even less at hypersonic speed. I agree that the electric compression can be the only part done electrically and letting kerosene take the place of the electric arc but then you don’t have an electric supersonic airplane anymore. Going supersonic on pure electric is therefore a very difficult endeavor. On the other end there could be potential benefits apart from quitting fossils. The e-fan to start with will not produce an IR spot which can be handy over enemy territory. The electric arc heating, although an enormous energy consumer, could give access to presently unknown plume speeds and thus provide incredible acceleration boosts, well at least if the pilot can take 9 g straight forward acceleration. There is no way an enemy missile can beat that or then of course an electric arc enemy missile.