WUWT reader “Non Nomen” writes:
Norway now wants to electrify domestic air traffic by 2040.
Will they be able to recharge at every overhead power line?
If they are on medication, they’d better stop that.
If not, they’d better take their pills.
Medication aside, I don’t think these people understand the concept and difficulty of scaling up such technology.
Here is another video worth watching:
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Maybe it would be more feasible without a pilot, just autopilot ?
Imagine the weight saving without cockpit etc.
The electric engine with just one moving part compared to hundreds is very nice.
IMO even over the next two decades, passengers are still going to want a pilot/attendant on board, even though most airliners now are essentially already operating on autopilot for at least most of the trip.
The weight savings in personnel however pales in comparison with that which could be saved by battery energy density gains.
People underestimate the improvements in batteries over the past few decades, ie from lead-acid to Ni-cad to Li ion, etc.
Tesla estimates advances in cost and power per unit weight of 7-8% per year. I’ll go with a more conservative 5% per year. That means a tripling in energy density in 20 years, without a breakthrough, just in incremental improvements.
If autopilot makes the ticket cheaper then people may accept it.
They are also experimenting with removing the passenger windows to save weight and increase strength.
Electric planes are so much quieter too – imagine the advantage of not having a curfew.
Electric planes are so much quieter too – imagine the advantage of not having a curfew.
Er no. They are not much quieter.
Most of the noise from an aircraft comes from either the propellors, or the sound of th exhaust of the jet engine.
The exhaust from a ducted fan doing the same job would be the same and so would the prop noise.
https://www.youtube.com/watch?v=A1SJS0B2NeA
listen. The ‘turbine whine’ and ‘jet roar’ are virtually the same as a real jet.
https://www.youtube.com/watch?v=O9VXCu1pbDk
Listen, The prop noise is just like a real plane!
“Felix
IMO even over the next two decades, passengers are still going to want a pilot/attendant on board, even though most airliners now are essentially already operating on autopilot for at least most of the trip.”
In 2000, Air New Zealand introduced a new in-flight cockpit safety policy called “The Pitbull”. It was a pitbull terrier dog to keep the pilots away from the controls.
/Joke
A lot of passengers have died from pilot error.
But a pit viper would be more energy efficient.
People overestimate the improvements in batteries over the past few decades, ie from lead-acid to Ni-cad to Li ion, etc.
You Felix being chief among them.
Speaking of weight savings, 3rd generation thin film PV cells might not weigh more than paint.
I did the sums. Lithium polymer is just about capable of an hours flight time with a reasonable load.
If Norway is small enough to be serviced by one hour flights, then its possible.
Not very economical, but possible.
Depends upon speeds. At 190 statute mph, Oslo to Bergen is about an hour. At 620 mph, Oslo to Narvik is around an hour.
But battery technology should be at least a third better than now by 2040, without major breakthroughs.
So the target is not a pie in the sky pipe dream, but not outside the realm of possibility.
The issue is whether a fleet of all electric passenger planes will make economic sense then. In a hydropower-rich country, maybe.
Hybrid electric will probably already make sense in the 2020s.
I suppose a battery to get you up to 3k AGL and then excellent soaring conditions. Ok, how many here hold a glider pilots license, raises hand,…. Hmmm oh well.
Rich mans summer toy. With commercial aircraft it’s not only the energy required to power the engines that thrust the plane through the air. You need power to drive all the flight surfaces, landing gear, cabin pressure etc etc…simply not possible with batteries at a commercial scale.
What about nuclear power?
What about shut-off and contamination in case of a crash or mid-air collision?
Well, my comment was a bit toungue-in-cheek, even though the US did develop an engine and it did fly in the 50’s or 60’s, Russia faked it, these were some of the concerns raised. Carrying the reactor that is shielded and it being crash/leak proof. Wasn’t going to happen then on a commercial scale, just like battery powered flight now for different reasons.
Actually, you are not very far off target. As you mentioned, there were attempts to get a bird flying with nuclear power, even in the US.
https://en.wikipedia.org/wiki/Aircraft_Nuclear_Propulsion
Nuclear power has considerable advantages but is paired with pretty inconvenient disadvantages.
Real world right now applications for aircraft electric power are:
Self launching sailplanes. There are a couple in production right now – the Lange Antares, the Pipstrel Taurus Electro and the Electro Silent and there is a system called FES which can be fitted to may sailplanes as a get you back home or to an airport.
Soon, perhaps some flight training will be carried out in electric aircraft like the one in the video.
Also soon for an aerobatic aircraft designed to operate not too far from the airport with a mission endurance of 30 to 45 minutes. getting it cross country to aerobatic contests will need to be done sailplane style on a trailer towed behind a car.
Glider towplane is possible also with spare battery packs but likely expensive.
Depends whether you want to share an airframe with a large incendiary bomb.
The REAL near future application is in VTOL flight which requires no magic tech.
The single largest problem with VTOL has been to deal with engine failure in VTOL and transition to/from wingborne flight modes. Solutions have been ejection seat (military only), autorotation (helicopters but they are horrible complex, expensive, maintenance hogs) and twin engines with expensive shafts and gearboxes (V-22 Osprey).
Distributed electric power for VTOL solves this problem. Use a conventional turbine or piston engine for cruise to get decent range and speed and at least 8 electric motors which only need two blade fixed pitch props (low maintenance). Battery power (only the safer LiFePO4 batteries required) only required for a couple of minutes after takeoff, and for emergencies such as engine failure. Simply glide to within a couple of hundred feet of the ground and start the electrics and go into VTOL mode to land in any area at least the size of the aircraft. Encounter bad weather? Just land and wait it out. High wing loading and tiny wings for comfortable ride and high speed cruise as you are never going to takeoff and land in conventional airplane mode. Landing gear needs to be much lighter and less strong for same reason. No unobtainium or “then magic happens” required.
See evtol.news for the 50 or so electric VTOL projects going on. These folks, for the main, are trying for pure electric which I think isn’t yet possible. I’d like a two seat VTOL homebuilt with 1000km range and 300km/hr cruise. Think of what private aviation could be if it didn’t need airports.
Light aircraft are a strange mix of the advanced and the ancient. You may for example find a ‘glass cockpit’ instrument panel coupled with an engine that requires you to adjust the mixture manually, like a 1920’s car.
The engines are very prone to temperature shock damage, which means you have to be careful over too rapid warming or cooling. That, and they run with a rich mixture, spewing pollution. Car engines overcame these issues decades ago.
They have an obsession with dual magneto ignition just in case of an electrical fault, yet use obsolete carburettor fuel metering which is prone to blockages, icing and flooding, and can equally well knock the engine out suddenly.
It wouldn’t be hard to improve on this. Battery power is not very practical though. One option might be a fuel cell and electric motor. Or, just a more modern IC engine. Rotax have taken steps in this direction but the aviation industry seems reluctant to accept anything that looks vaguely modern at the sharp end.
The aviation business is conservative, I should know having 40 years experience of it.
The reason is simple: “don’t fix it if it ain’t broke”. Aerospace equipment must have extreme reliability. ‘This is well-nigh impossible to achieve with new technology. For example the aerospace industry is always the last to abandon old processors and operating systems. They have had the bugs straightened out and are sufficient, so there is no reason to change.
In many cases, software for inspections and tests is still run off 3.5in floppies.
Norway also awards the Nobel Peace Prize.
Easy – nuclear batteries.
I think electric aircraft are a very niche market for the foreseeable future.
The trainer idea is sound, particularly if the next step is a jet (don’t waste time learning about piston engines, that you will not be using next).
An unmanned aircraft something like Solar Impulse with very long endurance has attractions doing satellite type jobs such as radio relay and surveillance.
Maybe they will eventually become useful as transports, but it is difficult to see the point.
Did you notice they stated there is no fuel cost?
These will be great in any location that has mostly consistent, clear weather with no electrical storms, etc.
Sounds like something Fenbeagle might invent.
https://fenbeagleblog.wordpress.com/
Flying coffin comes to mind.
Yes. It’s one thing to be able to get off the ground for a short flight under ideal conditions, and quite another to have sufficient reserve for safety margins. You can see people flying motorized ‘hang-gliders’ every day, and the accident rates are unacceptable. People are only now becoming aware of the dangers of high energy-density batteries. It is quite likely they have already reached their limit.
And it is still only short, low speed, flight. The jet engine displaced propellers for good reason in long distance flight.
And, of course, you have to go low level because a climb takes a helluvalot of precious energy. Have a look at the rugged and mountainous terrain of Norway, with fjords everywhere, such type of a/c must follow terrain through the valleys. Wind conditions and directions are unpredictable, and with a lack of power capacity you’ll either pancake your flying flea or have to ask the coast guard to pick you out of the cold water – Norwegian waters are cold, even in mid summer.
A great analysis on electric aircraft was done at Bjorne’s Corner by an actual aircraft engineer who is considered an opinion maker in the industry at https://leehamnews.com/?s=+electric+aircraft&submit=Go He walks through the design of the craft, tradeoffs, and economics. A good read, well commented by experts and worth the effort if one is interested. Felix might want to read it. There are performance and redundancy requirements set by law that are not addressed by most true believers.
Thanks, fine stuff!
In a 13-part series, he devotes only a bit of Part One to batteries, then goes straight to hybrids.
Battery tech is where it’s at.
I’m not a true believer in electric aviation. I just don’t think regional commercial prop planes by 2040 is a pipe dream.
This is all hype. Charles Lindbergh in 1927 did better than this “electric airplane of the future.” Build something comparable in performance to the 50-year old Boeing 747. Cruising speed 570 mph, range 7,550 miles, 440 passengers, cargo capacity 6,190 cu. ft. Don’t bother us with your lofty fantasy until you built the prototype
Maybe not a 747, but battery technology could support regional aviation by 2040.
Please read what VC guru Bill Joy said this month about solid (plastic or polymer) electrolyte Li-S battery development and its aviation potential:
https://spectrum.ieee.org/energywise/energy/the-smarter-grid/the-joy-of-batteries
Recent advances in PV cell tech also open up more of the spectrum to capture, to include UV and IR light. Which of course means that an electric plane could still generate power at night.
Polymer batteries, piezoelectric nanocrystals and other cutting edge research will be commercialized in this half century.
IMO people would benefit from studying more and scoffing less. Scams like Solyndra have given electric tech a bad name, as has its association with CACA spewers and subsidy farmers.
VC guru Bill Joy said, ” What I have is electricity, which can turn an electric motor. That’s more like a turboprop. So, someone smarter than me might have a way to do an equivalent of a 747 that’s electric. I don’t know how to do that. But I think regional jets and commuter jets and drones will be radically improved by it.”
Well I don’t know how to do that too but I know WHY I don’t know how to do that. Because the energy density of his Li-S battery is 500 wh/kg. Take a small airliner, the Saab 340, with 34 passengers. Its two turboprop engines produce 1300 kW each. Cruising speed 290 mph. Flying 3 hours, it travels 570 miles and consumes 7800 kWh energy. So the battery will weigh 15,600 kg. That’s almost twice the weight of the airplane (8140 kg) just the battery. He doesn’t meed someone smarter than him. He needs a magician to change the laws of physics.
Those aren’t the Li-S batteries of the company in which he has invested $65 million US.
The technologies he’s backing promise a three to ten-fold increase in energy density.
Nor would the first electric regional passenger planes fly routes of 870 miles. Nor does the battery energy density tell the whole story, with engine weight savings, PV cells, piezoelectric nanochrystals and airframe advances factored in. Etc.
Li2S8 = 270 g/mol
ave. voltage = 2.1 V
S8 => Li2S3 discharging, 5 electrons transfer = 10.5 eV = 4.7 e-22 wh x 6 e23 molecules/mol = 280 wh / 0.27 kg = 1037 wh/kg
That’s the best they can do. A factor of 2 improvement. Unless they can change laws of chemistry
The Li-S battery would still weigh 7,800 kg. The turboprop engine weighs only 198 kg.
Typo error: should be “870 miles”
Felix: This is just airy fairy handwavey magic thinking.
DO THE SUMS.
They dont add up.
I really don’t see the point of an electric vehicle that requires fossil fuels to charge it. It all cool and what not, but if the Alarmist want to knock a dent in CO2 emissions, they need to be focusing on new forms of energy …. preferably new forms capable of competing with fossil fuels or nuclear without completely covering the earth with bird killing windmills or surface covering solar panels or mirrors.
Aside from efficiency of end product, which I cant see this as being an increase in efficiency, all this electric toy does is move emissions from the vehicle to a power plant.
Norway is hydroelectric. And there is always nuclear.
An all nuclear/electric society is actually very feasible, apart from transport.
Ships can be nuclear. Trains can be electric. But portable power (cars/boats/planes) is still a hydrocarbon fuel UNLESS lithium air batteries can be made to work OR we come up with a technology no one has even thought of yet, because (and this is addressed to YOU Felix) we can calculate how good any technology we HAVE thought of CAN be THEORETICALLY and if its not good enough THEORETICALLY its sure as heck ain’t gonna be good enough in practice.
And you guessed it, windmills solar panels aluminum air batteries lithium polymer batteries super capacitors all can’t even do the job theoretically.
And hoping that throwing money at them, will, is simply childish delusion.
Some technologies are close – like windmills solar panels and lithium polymer, close enough so that by using the surplus energy we have in cheap fossil fuel they can appear to actually be viable…
But on their own they are not.
Si-air batteries work with refilling the electrolyte solution. Next step will be replacing liquid electrolyte with solid.
https://phys.org/news/2016-07-silicon-air-battery-hours.html
Progress marches on.
How many of these wonderful magic battery concepts have there been in recent decades?
How many have made it to a actual useful batteries?
Sometimes right off a cliff.
Even using it as a trainer bothers me since the response to throttle changes is so different between electric and IC motors. Just switching from an electric to an IC powered aircraft can get you killed.
I am surprised that they did not mandate these planes carry a windmill at the back to charge the battery. So much wind energy is wasted when the plane is flying.
Or with props.
But PV cells on the wings will also recharge the batteries and run the engines directly.
The efficiency of PV cells isn’t really thrilling. They also add some weight, plus extra wiring and charge controllers.
Third generation PV cells will improve efficiency.
Plus, we can now access the whole spectrum from UV to IR.
You still Cant Do Sums, can you, Felix.
Ignorance must be bliss: You read stuff and you Believe, and the world is a hopeful rosy place of fantastic dreams .
I was like that when I was 7. But unlike you, I wanted to make those dreams come true.
At 7 I built my first and only perpetual motion machine out of Meccano.
It simply locked up solid and wouldn’t turn.
10 years later with A level physics and maths, I understood why.
14 years later with a Cambridge degree in engineering, I knew nearly all there was to know about the theory of machines. And electricity and electronics.
And realized that outside of some unknowable breakthrough, most of what I dreamt of as a child was impossible.
I mentor students these days., One Russian kid came and said ‘why cannot we have vertical take off jet planes?
I said ‘we can, but it takes huge power’ he said ‘but a helicopter does not’ and then I tried to explain the difference between power and thrust, energy and momentum. This guy is a Cambridge student FFS and he doesn’t appear to understand this…
You are a dreamer and a believer Felix.
I am on old tired engineer, who has been building stuff, most of which eventually worked, or was proven not to be able to ever work, all his life.
And that is the key phrase, ‘been proven not to work’.
I can prove that solar panels wind,mills and electric planes wont work. Not without some as yet undreamed of technology. Not commercially. Of course they all work as examples of what can be done, but that is not the same as being viable economically.
Because that is the second lesson an engineer learns – lots of stuff works, but is still useless.
‘An engineer is someone who can build for five bob what any damned fool can build for a quid’
.Why subsidise technology that barely works when we already have stuff that works better and is cheaper? There is no good reaosn except to employ more people.
Why not just give them the money instead of employing them?
It’s actually CHEAPER. We are paying people to rush around, go to work and consume vast amounts of energy to build stuff that doesn’t work, instead of paying them to stay at home and have a nice relaxed life.
What is the point?
Its all head games, its all about making stupid people feel good about themselves ‘saving the planet’ ‘social justice’ etc etc.
Well Felix, I hope you feel good about yourself, you roll up another fat one, and bliss out, sunshine, but please., leave the job of running the world you so casually take for granted, to people like me, who actually understand how technology works.
If we ever succeed at starting a stable, controlled fusion reaction, we could produce beryllium as a byproduct. With an aluminum-sheathed beryllium airframe and no shortage of energy for charging batts, we could take a second look at fully electric commercial aircraft. If.
If you put a wind turbine in airplane, it will produce drag, the opposite of thrust generated by a propeller. Efficiencies: electric generator = 95%, battery = 90%, electric motor = 95%, propeller = 85%
Overall efficiency = 0.95 x 0.9 x 0.95 x 0.85 = 0.69
So if the turbine makes 1 lb drag, the propeller makes 0.69 lb thrust. Net 0.31 lb drag. That’s why nobody puts wind turbine in airplane. It only slows it down and wastes energy
Well…Take an ATR 42, an otherwise considered as awfully underpowered 48 seater common on (very) low cost regional routes, sports a total power in the range of 4’000 HP for the less gifted engine versions.
Very few pilots genuinely like to fly it. Thin extremely prone to icing wings and marginal power reserve are amongst the features that build it’s fuel economy and widow making potential reputation.
Now, how could an electric powered airframe with similar MTOW compete in the process, even with this reference of what most consider minimal for airworthiness power figures ?
Hey folks, try to be serious already. At turboprop altitudes the ambient temperature is in the -25 Celsius and downwards.
Jet fuel does not mind being that and even more cold. Nor do the turbines BTW. Their efficiency even increases with cold intake air.
The temperature management of the batteries will be a very demanding science fiction project.
Passenger flights above 8’000 feet require cabin pressurization with corresponding air renewal. Quite energy demanding indeed. Reason why you’re not allowed to smoke anymore on planes due to intensive cabin air recycling, but that’s another story. Good thing, cockpit air is not recycled so…
The main reason for planes to fly high is the benefit from thinner air and consequent drag reduction. Which would be actually welcome for airframes with marginal battery energy storage capabilities.
Now throw the pressurization constraints and voila, you have yourself a more realistic picture of why climate militant NGO’s are not the most appropriate aviation schools.
Nope, planes are not forklifts, they do not use their on-board batteries as ballast weight for increased stability while carrying loads.
Flying above the cloud deck means more photon “fuel”.
Solid state batteries will be less susceptible to cold.
In case you subscribe to Aviation Leak, this article from April reports on progress of Siemens’ electric aircraft program, on both hybrid and pure electric engines.
Correction. Polymer solid state batteries would be. Older ceramic batteries are indeed susceptible to cold:
http://www.ehcar.net/library/rapport/rapport206.pdf
Felix, congratulations, is that all you could afford to understand from or my post and google around for answers ?
Commercial aviation is a very serious trade.
My scope is not to prevent you from flying solo whatever pleases you over unpopulated areas and far enough from our airspaces. Even more, please do so, you’ll learn quite a lot in the process.
However we have a far greater respect for human life and can not afford to impose armchair fantasies on people who trusted us the most by stepping on our board.
Even with a supposed efficiency of 100% of future magic PV cells, solar A/C’s will have the flying envelope of a kite.
Because their performances do not depend on the airframe surface area. Yep. Do the maths, see for yourself, it cancels out on both sides of the constant speed level flight energy balance equation for PV powered planes.
On the other hand, a quick estimation of 747 flying a New York to Paris route requires a pure mechanical energy equivalent to 5’000 tons of TESLA automotive battery packs. And even more if real world efficiencies are introduced in the estimation…
Add a quite few more for regulatory reserves. In other words, good luck to stuff all this in the 747 and lift up (or even move) with more than a 15 times MTOW overload factor.
Aircraft propulsion can be assimilated to what happens in a vacuum cleaner. Quickly moving air, an awful lot of it.
Reason why a mains powered unit will outperform big time even the best cordless portable self contained battery operated vac of similar weight.
Planes are not trains, last time I called it for the day, there was not even a single pantograph item on the checklist. But promised, I’ll check on Monday, just in case I’ve been careless enough to miss it.
Consequently your best bet could be to lobby for electrified air corridors and pilots desperate enough to fly in them. Good luck on both counts.
No one is yet proposing an electric 747, although work is progressing on electric and hybrid jet engines.
Your airframe design issues apply only to a pure PV cell a/c, which is not in the offing for passenger service. A commercial a/c would not be a kite. It would include batteries with sufficient power to propel a heavier airframe. PV cells could be integrated into a conventional design, although the propulsor option constitutes something of a departure from traditional design.
The engineers working on electric aircraft design and power pack development have at least as much concern for passenger safety as do you. My middle name is honor of an ex-Navy United pilot. I number at least a dozen ex-military commercial pilots among my friends and even a few civilians.
I don’t own an electric sport plane, but might buy one in future. I do fly over largely unpopulated areas, and any workable design is liable to be akin to a glider. If not in fact a glider with an electric engine for TO.
My Googling around led me to discover that even older style glass Li batteries are good down to -20 degrees C. Si-air batteries however have the advantages of greater safety and lower cost than Li, with nearly the same high energy density, theoretically comparable to gasoline.
Well Felix, let me disclose to you and all other greenwashed armchair pilots that weight induces drag. The infamous lift induced drag. Quite a spectacular one indeed as it decreases with speed.
However for this to happen, the A/C should be able to reach sufficient airspeed and overcome the parasitic drag which drastically increases with speed.
Consequently, all the industry is oriented towards weight reduction, amongst other.
Except greenwashed armchair pilots, those who pretend that the comparatively excessive weight of batteries is somehow beneficial to a viable and reliable aviation.
Purposely ignoring all inherent realities and physics of flight.
Which is a form of terrorism, intellectual terrorism.
The future will sort out the physics as it has never failed to do in the past.
Hopefully without claiming too many innocent lives.
Till then and even after, we’ll fly you around safely. Including to climate conferences and other similar junkets.
You’re attacking a strawman. I didn’t say that greater weight was an aerodynamic plus, just that electric planes won’t be kites.
Battery tech actually promises less weight on TO than full fuel tanks. The drawback is that you won’t get lighter with time.
I’m not greenwashed. I’m a hard core CACA skeptic. But that doesn’t mean that we shouldn’t pursue better battery technology. When and where its physically and economically competitive, it will be preferable to burning such a rich mix of compounds as petroleum, with which so much else can be done.
Trans-Pacific flight in stratospheric jumbo jets is likely to remain JP-fueled for the foreseeable future. But that need not apply to short-haul passenger traffic. Not because of emissions but economics.
Yes Felix, why dont you buzz off and pursue better battery technology, and when you have found it, make yourself a billionaire on the back of it.
Until then, you remind me of this song.,
Again another straw man. (I agree about the awfulness of an ATR 42, having been stuck for 6 hours with one that they dare not fly due to lack of airport deicing equipment)
Batteries need cooling. It is trivial to insulate them against cold, and use their internally generated heat to keep them warm, or open up slots on the insulation to cool them if they overheat. Its no more difficult than e.g. controlling an air cooled piston engine.
Cabin pressurization is again a trivial matter of an electric air pump.
Other straw men include lack of weight loss in flight , insufficient power, and lack of speed.
In reality theere is only one thing between now and battery electric passenger aircraft.
Battery energy density.
Leonardo da Vinci sketched out designs of planes. We could have had powered flight in the 1600s. IF we had had a high power to weight motor of some kind. But we had to wait till metallurgy produced lightweight strong steels and alloys, till steam had shown how to build engines, and until petroleum gave us the fuel, and internal combustion showed us how to use that fuel and the air it needed to burn as the working fluid in an engine, instead of carrying water to make steam.
All that, just to have an engine that could fly a plane.
In the same way all we are lacking in electric off-grid transport is a suitable battery. About 10 times better in energy density and still safe to handle than what we have now.
That’s all.
Problem is, no battery is even theoretically capable of 10 times current performance, except lithium air. And thats almost impossible to make a safe practical battery out of.
Like windmills and solar panels, transport batteries are so tantalizingly close to actually being viable, except that the physics shows they are all not and never will be. They have to be supported on the backs of other technologies…and subsidized.
The car shown in the video. Is a Tesla. Tesla is the only company to be investigating WiFi power. Perhaps WiFi is the way to go?
Another thing, how does an aircraft power consumption breakdown during a trip? Does take off require greater power consumption than flying? If so ground charging is vastly uneconomic. Perhaps charging from airships might become feasible?
Just thoughts, you know, just thoughts.
Naturally power settings at cruise are lower than during TO. It’s common for instance for naval patrol P-3s to feather one of their four engines once at altitude.
Very easy to calculate. If you Can Do Sums. Unlike Felix…
Take an aircraft with a glide angle of one in 20. (thats the same as lift to drag ratio really and is about Airbus 380 standard) flying at 450 mph…
That is very nearly exactly 200 meters per second, so without power it’s losing altitude at a rate of 10 meters per second in a glide.
In order to counteract that it needs a power input of about 98 – say 100 watts per kilogram, to stay in cruise.
Add another 100W/kg and it will climb at 20 meters per second.
An airbus will climb at around 1000 fpm. Or 5 meters per second. So for climb out it needs another 25 watts per kg.
Takeoff probably even more again.
So let’s say to operate an aircraft with an effective cruise speed of 450 mph needs a power to weight ratio of 150 watts per kg to climb and 100 watts per kg to cruise. And that’s a state of the art airframe.
An airbus weighs in at 500 metric tonnes fully loaded so it needs 500,000 x 150W = 75MW takeoff/climb power and 50MW to stay in level flight.
Now to cross the Atlantic – 3500 miles from London to New York more or less, at 450mph takes 7.77 hours. Let’s round that up to 8.
So the battery needs to be around 400 MWh
Obviously the power taken to get up to cruise is power you can subtract from getting down again. So I have used cruise power.
I have totally IGNORED drive train efficiency. battery to shaft will be good 90% or better – but shaft to thrust will be worse. Probably no better than 60%.
Lets say 50% overall.
So in reality we need an 800MWh battery.
How much would such a battery weigh?
https://www.aliexpress.com/item/Newest-405585-Lithium-Polymer-Battery-3-7V-2500mAh-Li-ion-Rechargeable-Accumulator-For-Mobile-Power-Bank/32515193445.html
Is a typical battery without casing or protection and is 3000Ah at 3.7V – and weighs in at 48g, so thats 230watt hours per kg
So a li-Poly battery bank to get us 800 MWh is about 3500 metric tonnes. Oh dear that’s seven times the weight of the aircraft!
It is simply impossible.
Let’s look at how much energy density we WOULD need to do the job.
There’s 200 tonnes of fuel and passengers in an Airbus 380 and 800 passengers. Let’s say with luggage they are 100kg each so thats , so lets assume a payload of around 80 metric tonnes.
Leaving 120 tonnes of fuel – well it can carry 80, 000 gallons or 300 cubic meters or around 240 metric tonnes.
So how much duration would standard batteries of this weight get us? We can cram in about 55MWh so just about half an hour’s flight.
What energy density would we need to achieve to get across the Atlantic? Well we need 800MWh in 240 tonnes give or take And that’s still only half the range of a kerosene powered jet.
800Mwh and 240 tonnes is 800kwh and 240 kg so 3300 watt hours per kg.
As I said a reasonable off the shelf Li Poly is around 230 watt hours per kg.
What wiki has to say about lithium batteries is this:
Each gram of lithium represents Faraday’s constant/6.941 or 13,901 coulombs. At 3 V, this gives 41.7 kJ per gram of lithium, or 11.6 kWh per kg. This is a bit more than the heat of combustion of gasoline, but does not consider the other materials that go into a lithium battery and that make lithium batteries many times heavier per unit of energy.
So in theory lithium has the requisite energy density, but in practice it does not.
Because lithium alone is not a battery.
Lithium air is described in Wiki as follows:
Pairing lithium and ambient oxygen can theoretically lead to electrochemical cells with the highest possible specific energy. Indeed, the theoretical specific energy of a non-aqueous Li-air battery, in the charged state with Li2O2 product and excluding the oxygen mass, is ~40.1 MJ/kg. This is comparable to the theoretical specific energy of gasoline, ~46.8 MJ/kg.
Pairing lithium and ambient oxygen can theoretically lead to electrochemical cells with the highest possible specific energy. Indeed, the theoretical specific energy of a non-aqueous Li-air battery, in the charged state with Li2O2 product and excluding the oxygen mass, is ~40.1 MJ/kg. This is comparable to the theoretical specific energy of gasoline, ~46.8 MJ/kg. In practice, Li-air batteries with a specific energy of ~6.12 MJ/kg at the cell level have been demonstrated. This is about 5 times greater than that of a commercial lithium-ion battery
6.12MJ/kg is about 1700 watt hours per kg. Still less than half what we need to get us across the Atlantic.
And that in a nutshell is the Big Sums that tell us where the electric Airbus is at.
Forget solar panels hybrids and the like, the sums on those don’t make sense either. Cruise power is less, bit not markedly less, than takeoff and climb power, so hybrid is not worth doing. The solar energy falling in the wing is at best (full tropical midday sun) 850Kw with probably only 200KW actual electrical output when we need 50MW to stay aloft.
What wee need is a battery at least 12 times better than state of the art lithium polymer, which is the best energy density in common usage to get half the range of the airbus 380, though we can get to New York from London. To match fuel we probably need around 20 times better battery – 5000 watts per kg.
the theoretical energy density of lithium air is 11,000 watts per kg. But so far all we have achieved is 1,700 wh/kg ..but that’s the closest. Double that to 3,400 watt per kg and we are able to get across the Atlantic with passengers at 450mph.
Thats how near and yet how far we are away from viable commercial electrical flight.
Current production technology gets us a couple of hundred miles range max. Best battery ever made maybe 1500 miles range, and it’s a lab scale battery.
We have to match 30% of what lithium air is theoretically capable of to get transatlantic flight and about 70% of what its theoretically capable of to match the range of modern airliners.
So far we have achieved 15% in the lab…only.
Now there is something else that is worth saying. These figures are independent of speed. In essence the energy needed to get a given wight of plane a given distance is simply a function of the glide angle – the lift to drag ratio. Commercially it pays to do that as fast as possible to get more paying passenger miles per year, and as fast as possible means 40,000 feet and Mach 0.85 because that is where the best speed and lift to drag rations can be found.
The final thing I want to add to this, for the Felixes of this world, is to show how it only takes an hour – thats how long this post has taken, – to cut through all the cockwomble and flapdoodle of – say – Electric flight, down to the crucial bare essentials of the numbers and the technology. I accept I am in a particularly privileged position to do this in this case, because I have a class degree in engineering that includes all forms of it – fluid dynamics. structures and materials, theory of heat engines and electricity and machines, plus 5 years spent pushing electric model planes to the limit and doing the theoretical calculations on them, so this is not new ground for me, but the point remains. In an hour I can say with a high degree of assurance where the technology is at, where it could be at and where it most certainly never will be at.
Because I know physics , chemistry, engineering and maths. And can Do Sums.
Starting from the basics of lift to drag ratios (glide angles) its possible to easily calculate how many watt hours per kilogram we need to get across the Atlantic in any plane. In the end NOTHING ELSE MATTERS.
Experience of electric models shows that drive train efficiencies are around 50%. For an geared propellor at 50mph sort of speeds. Thats the inverse of the Betz equations for wind turbines that give a theoretical 67% max efficiency for a wind turbine. Ducted fans are far less efficient at model plane speeds, but theory suggests they could do better than Betz limits at the right airspeed. so 50%-60% is in the ballpark at 450mph +-.
Then we can go to the basic electro chemistry and get figures for best theoretical energy density of lithium, which is the best battery material there is.
And that makes it look all possible, except we have the practical matter of constructing a real life battery.
And we have a simple dichotomy. In theory a lithium battery COULD fly a ‘leccy plane as well or better than fuel but in practice…it cannot.
Its like looking at the energy density of plutonium – 80,620,000 MJ/kg or around 22394444444 watt hours per kg and saying that essentially a kg of plutonium would fly an airbus one and a half million miles….except that we need a safe way to turn that energy into thrust that doesn’t weigh hundreds of tonnes and leave a radioactive wake…
The problem is that any practical lithium battery involves another electrode and some sort of electrolyte, and these mean weight.
And that means we are unable to achieve the theoretical energy densities of lithium alone.
All the above, means that when I say ‘the whole problem resolves to one of energy density and nothing else matters’ that is not an ‘opinion’. That is what the physics and maths says. Backed up by experience.
And when I say ‘although in theory a lithium air battery might be able to get an Airbus across the Atlantic, in practice its a considerable way off at the moment’ again that is not ‘opinion’ but facts derived from basic electro chemistry, and the practical state of battery technology.
Someone ought to be paying me to stop people investing in stuff that will never work…
It occurs to me that the above is worth a post of its own, if Anthony feels likewise..
I think You forgot to factor in one thing. Lithium-air batteries work on the reaction Li + O2 -> LiO2. That means that one ton of lithium at take-off will change to seven tons of lithium dioxide during the flight.
But we can look on the bright side. There wouldn’t be any new MH370 mysteries. Seismographs could easily pinpoint where an aircraft with several tons of lithium metal onboard went into the sea.
Worse, Li-air battery has carbon cathode. At best, it produces 500 A/kg of C at 1.8 V
Power = 500 (1.8) = 900 W/kg
Small turboprop engine can generate 1300 kW. To match that power, you need
1300,000/900 = 1,444 kg of carbon
That’s just the cathode of the Li-air battery. The turboprop engine weighs only 198 kg
He told the truth, Bravo!
“Could be done” is not the same as ‘”economically viable”
It’s just another way of getting funding for climate-related schemes. The founder of Norwegian Air Shuttle, Mr. Kjos, recommended that the money for research of e-planes should be given to UNICEF. He said this may happen some 50 years from now, but that it is the job of airplane builders, not a government, to develop this technology.
This is absolutely no problem. All we need, is to make smaller humans. This can be achieved by forcibly and drastically reducing the intake of nutritients, thereby also reducing the climate-destroying agricultural footprint of humanity. Footprints in general will of course also become smaller.
To get some perspective. Electrical planes have about the same performance today that conventional aircraft had in 1908, five years after Kitty Hawk.
From that point it took about 15 years to small-scale, short-haul commercial operations and 30 years to the first small-scale trans-oceanic operations. Non-stop operations across the Atlantic took 40 years.
And this was with accelerated technical developments during two world wars to help. And it could all be done by incremental improvements of technology, while long-haul electrical aircraft will require some new, and at present quite unknown, storage technology.
Long-haul electrical aircraft before 2050 is extremely unlikely, and most likely will never happen at all.
In a few hours we’ll throw matches in and spool props up in excess of 8’000 horse power to safely carry 4 dozens of souls from A to B.
Even so with, ok, a somehow comfortable power reserve, we’ll spend time to consider the weather and decide on the safest procedures to cope with it’s inherent stochastic variability and provide for safe fuel (think energy) reserves.
Then fill the numbers, add some on our appreciation and check the reading of the fueler meters.
Just a very abbreviated description on how seriously we feed our powerplants.
Because should it be, we all depend on whatever happens when we push forwards the levers. At any moment, without much warning, all those behind, cabin crew and finally ourselves depend on available power, lots of it, for as long as it takes.
Reliable power is cardinal for airspeed and altitude, there’s no tow truck that we can call in mid-air, go-round’s, alternates, weather sandwiches.
That’s how much the overly simplistic energy to weight ratio matters in the trade.
Today, roughly speaking, jet fuel offers 15 times more energy reserve per weight when compared to the best and most optimistic battery promises in lab conditions.
Which sets electric battery powered aviation on pair with diesel locomotives at best.
Ever wonder why locs do not commonly fly ? Or why electric trains trains have pantographs ?
In aviation, “range anxiety” spells “death and destruction”. Good luck with that.
It makes for good innocent fun to apply the ICAO fuel reserve requirements for General Aviation to an aircraft with a 1 hour endurance and about 85 mph cruise.
1) VFR: to destination + 30 minutes
2) VFR at night: to destination + 45 minutes
3) IFR: to destination, then to designated alternate + 45 minutes
In case 1) you have a practical range of about 40 miles (30 minutes) in 2) about 20 miles (15 minutes) and in case 3) 10 miles (7,5 minutes, if designating take-off site as alternate).
That’s how aerial refueling, sorry, quick-charging, became mandatory in GA.
Long-haul isn’t the issue.
For 2040, we’re talking Bombardier Dash 8, tops, not Boeing 737 (granted a bit of overlap), let alone 747.
Given the periodic table, the max power density of the best battery conceivable today just about equals gasoline. But the whole system power pack has to be weighed, not just the “fuel”.
Whether via incremental improvements, or a big breakthrough, batteries are going to improve over the next 22 years.
If widespread adoption of electric a/c even occurs, it’s liable to proceed from its present RC, quadcopter drones and two seat toys to four seat light plane to very short hop small transports to regional commuter liners with a dozen to two dozen to three dozen to four dozen passengers. Those steps could occur in the ’20s and ’30s, but it all comes down to battery development. And maybe the speed with which third generation PV cells advance.
As noted, thin film 3rd gen might not weigh more than paint. Just a WAG on my part. But I’m a technological optimist.
Felix, and the shaft horse power of DASH-8 300 is ? And even then, it’s a sad to fly bird in icing conditions. Think, Norway, north, wet sludgy snow, a bit of quick sun, clear ice…
This morning, quite some south of 49, bumby enough to cancel coffee pouring, at 8’000 feet shields-up for the descent, just saying, would you think icing in june ? Very satisfactory to know that we carry enough of what it takes to make the call and get out to better skies if needed.
And you dream that a cap in right mind will let PAX board an electric flying coffin ? What’s up, recharging stations on clouds ? Hey, grow up kids…
How many people do you greens want to kill, each and every way ? Is that a mandatory save-the-earth strategy ?
no backup . and if batteries go to fire mode?
might train a pilot but then a normal planes going to be vastly different to handle.
i wouldnt get in one
It might work if you go directly on to a jet, and never fly an IC-powered aircraft. But nowadays it is becoming normal to use a jet trainer from the start.