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The future of the helicopter is electric.

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The future of the helicopter is electric.

Old 20th May 2004, 11:36
  #21 (permalink)  
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Why would you want to use batteries ?

My craizy theory is that for more than 30 years Oil companies have (partially) sponsored battery research projects in the car industry to make shure we would still use lots of fosil fuels, because batteries simply are not the answer.
One of the interesting research outcomes is for instance that using a small solar panel, driving a little fan can efficiently cool the car in the summer on the parking : bid deal ...

A small calculation shows how inefficient batteries are :

A diesel can get 30-38% effficiency.
A fosile power plant max 38%, Nuclear because of safety 33%, say average 35%
Transmission efficiency is 95%, battery loading 95%, electrical motor efficiency 90%.
Together : 35%*95%*95%*90%= 28%
Storage, distribution of fuel is far easier, the current power system simply cannot transport these amounts, certainly not if peak power is wanted (for charging).

The remaining 60% in cars and helicopters is also used for heating, so the total 'co-generation' efficiency is higher than 30-38%, I would say by at least 5%, certainly in helicopters where you tend to encounter colder air.

Ecologically speaking : what to do with all the cupper and most important the batteries that are far from ecological.

I would stick to a diesel.
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Old 21st May 2004, 17:12
  #22 (permalink)  
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Thanks for your thoughts everyone, but there are some real misconceptions here which need looking at. Delta3 makes a point about transmission efficiency which is fair enough but his numbers come from... well, the top of his head probably.

A coal-fired power station is several times more efficient than a coal-fired steam engine, easily overcoming the transmission loss from high-tension cables. The same goes for any other type of primary fuel. The fact that batteries are a 'secondary' power source is simply not a problem from an efficiency point of view.

His point about electric car development is partially true. Ford and GM are busy recalling and scrapping the electric vehicles they designed for California beacause they're too good.

Instead we have the idea of hydrogen as a scondary fuel. Now this is a seriously flawed, and plenty of people believe the fuel-cell is a deliberate diversion by the oil industry.

Further reading at EV World article

Hoss 1's story about the Orlando experiment is the best lead so far.... care to tell us more, Hoss 1?

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Old 23rd May 2004, 06:22
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I saw your posting for the first time last night. I am in the camp that say that present battery technology is what limits your idea from being applied.

I did have a look on the net to see what the performance figures for rechargeable batteries were. Some recent research anticipates an energy density of about 1000Kj/Kg (a very rough guide).

Suppose an R22 needs 90 hp (or 67 Kw) of power to cruise and supposing these batteries weigh what a full load of fuel would weigh in an R22: 81 Kg. Then you have on board 81000 Kj of energy which your motor would use at a rate of 67 Kj per second. You have power to cruise for 81000/67=1209 seconds or just over 20 minutes.

A seven or eightfold increase in battery energy density is needed before the idea becomes practical, I would guess.
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Old 23rd May 2004, 12:30
  #24 (permalink)  
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Ok, so bypassing the flat/round electron arguments on this one (although personally I'd think flat ones would be more practical purely on storage grounds), the main restriction point on this one would seem to be battery technology.
So.... in a car, the battery is used to provide energy to operate the starter and then as a constantly topped up reservoir for all other electrical usage (assuming the alternator is working).
So (2)... why not have this E22 or R22e set up to have two drive motors (both driving a main gb as per a normal twin) and also driving a pair of (or just one) high output alternators. You'd still have batteries, but only sufficient storage to run up to initial speed until the alts took over and also provide say 5 mins power should both alts fail - thus enough for say 2 mins emergency manouvering or to get safely into auto.
Granted, the oil companies would do everything possible to avoid the idea getting anywhere, but once it got certified, even with a slightly higher initial cost, I could see them selling very well indeed..... no fuel costs, massively reduced engine maint costs... the pollution bonus, the noise bonus. Potentially, could do masses for the whole helo industry.

But that's just my 2 penneth, not that I don't love the smell of avtur in the morning.... cos I don't
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Old 23rd May 2004, 19:09
  #25 (permalink)  
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Lightbulb 'Empty weight' is the bane of rotorcraft.

Decreasing the weight of the fuselage, the rotor and the power-train by using plastics (composite construction) will be a significant improvement.

Combining this with the previously mentioned plastic battery, and one can envision the eventual possibility of the fuselage being the battery.

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Old 23rd May 2004, 22:37
  #26 (permalink)  
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Thumbs up

Maybe I'm being too narrow minded, but I just don't think you will ever see batteries (stored energy using inverters or whatever similar gadget) as the primary power source for rotorcraft. You might get away with that for fixed wing, because they can turn the prop on and off when needed (& they can generally carry more weight). If it's going to happen in a rotorcraft, my money is on a hydrogen system that provides energy directly to a fuel cell, which provides power for the electric motor and systems. Again, fuel cell technology is coming along nicely... how to carry enough hydrogen (safely) is the real problem.

Heck, you can purchase a retail version of a fuel cell power generator that will provide 1,000 watts of electricity as long as hydrogen gas is supplied. It's quite, nearly maintenance free, and was designed to run INDOORS (you don't have to worry about CO poisoning in the cockpit)...



So, how can you carry enough H2 fuel (read throughput) for the larger systems (currently used in Ford & Chrystler protypes)? For rotorcraft, it just can't be done... today. That's just one challenge. With this kind of configuration, it is likely that you will need a complicated transmission to maintain RRPM in all fight regimes... simply adding more power or less power might not be an option anymore.
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Old 24th May 2004, 03:06
  #27 (permalink)  
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you are pretty far off in all of your opening premises:

- Electric motors are a lot lighter than piston engines

Not at all true. Typical piston engines are about 1/3 the weight of an equivilent electric motor. For example, a 150 HP electric motor weighs 1350 lbs, while a 180 HP Lycoming weighs 257 lbs. Even if we assume that we could get an electric motor to trim 3/4 of its weight, it would still be far heavier than a piston engine.
here are some facts


- Electric motors are way more efficient
Hardly electric motors are not engines, they are actually a form of transmission. they need raw energy to work, unlike engines, which create energy in their process. Since you don't include how the electricity is made into your assumption, you believe that the electric motor wastes less, but that is actually quite false. since someone somewhere had to make the electricity, you must count that inefficiency in, and so far, no total process is much more efficient than a simple engine. Fuel cells are the exception, and should they work out in high capacity, there might be parity in the efficiency, but of course, the weight of the fuel cell must be counted in, and they are quite heavy in high power designs, so far.

- Startup, shutdown and carb icing wouldn't be problems any more
True, but then we'd have "relay freeze" or "spark jump" or some other set of problems! Remember what the side of Apollo 13 looked like when the fuel cell exploded?

- There would be a lot less moving parts, and reliability would be increased
See Above!

- The end result would be eco-friendly and very cheap to run!
Eco-Friendly, right. And cleaner clothes, smoother white teeth, with that fresh lemon scent!

The solution to electric air vehicles is very far off, mostly weight problems, mostly in the energy storage area. Fuel cells are the best solution, along with very light weight motors and lots and lots of development time and money.

A more likely solution is to make cheap electric power with reactors (fusion, perhaps) use the electricity to split water into hydrogen, compress it into liquid and run gas turbines in the flying machines on that hydrogen with zero emissions
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Old 24th May 2004, 13:15
  #28 (permalink)  
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Lightbulb air combustion?

why not just compressed air? diving below, is it 80 metres?, they breath helium (or a mixture) so the air doesnt explode. this would be around 90 times the attmesphere. would need a good stroke on the crank i spose or maybe it takes more energy to compress the air than the explosion makes??
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Old 24th May 2004, 14:11
  #29 (permalink)  
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Just storing energy won't work, because the aircraft needs so much of it. If you squeeze air into a bottle and then let it out into an engine, you get less than you put in. If you bring some gasoline, you get a tremendous return on its weight. For example, a pound of air squeezed to 90 atmospheres has about 2.6 million ft-lbs of stored energy in it. If it were used in 1 minute, it has a total of 78 Horsepower for that minute. If a pound of gasoline were compared, it has 14 million ft-lbs of energy in it, and delivers 424 Horsepower if burned in 1 minute.

In other words, fuel is about 5 times more weight efficient when compared to stored air. And we didn't figure in the weight of a compressed bottle as compared to a fuel tank. My guess is the bottle would have to be 5 to 10 times heavier than the fuel tank, a further penalty.

You have also pointed out why electricity is so poor in flying machines. Recall that the electric motor needs to have energy delivered to it, so it needs to be fed those enoumous amounts of energy to make the power, and that energy is hard to come by.

PS they breath helium at great depth because of nitrogen narcosis, not because of explosions. At high pressure, nitrogen is an anesthetic and makes you high! Helium only makes you talk like Donald Duck.
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Old 24th May 2004, 19:12
  #30 (permalink)  
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Nick, I have to disagree with you here.

I wasn't able to download the PDF you linked to, but you're definitely looking in the wrong place for your electric motor. Perhaps the one you found was designed for elevator installations? The one I found here delivers a lot more power than your Lycoming and weighs 180lb including its cooling system so don't forget to take off the squirrel cage!

I know my batteries are going to be heavier than a fuel tank. But I'm also taking out both gearboxes, the mechanical drive shaft, the oil cooler, the clutch, the alternator, the starter motor and any other IC-related things I can think of...

I don't have the slightest intention to use fuel cells. They have a very poor energy density and the usage problems you describe. Nor would I use hydrogen - current storage methods involve a high-pressure tank storing liquid hydrogen, and the energy density of the tank + hydrogen is way below the current best offered by batteries. Chemical batteries are the closest thing to gasoline, as described at the EVWorld link in my previous post.

You're right about electricity being a 'secondary' power source; something has to burn or turn somewhere to generate the electricity. You overestimate the transmission losses, which leads you to conclude that a primary power source is more efficient than a chain which includes stored electricity. This would be true if small internal combustion engines were at all efficient. Do the math: 65% efficiency in a power station vs 10-15% efficiency in a small IC engine. There's a lot of leeway for transmission losses in my electricity chain!

Keep up the counter-arguments though...


Last edited by Benet; 24th May 2004 at 19:30.
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Old 24th May 2004, 22:20
  #31 (permalink)  
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Good data, Benet, but bad math. That 180 lb motor you found is nice, but it is only 70 HP continuous power!

Also, no power plant on the planet has more than 50% efficiency (unless they repealed Carnot's cycle), most are around 35% or so. Some experimental plant models get 40% as do fuel cells.

The total system efficiency is the product of the 35% (power plant) x the 90% transmission x the 86% of the motor for a net 27%, about the same for a good gas powered piston engine. My Honda a few years ago was 24% efficient on the highway at 60mph!

And that does not include the massive battery system, nor the 350 lbs for the motor (2 x the 70 HP motor you found).

Still a long way off, and not closing, I think. But a good fact finding debate, nonetheless!
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Old 25th May 2004, 22:15
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There are electric motors using rare earth magnets and brushless commentators that have a horsepower to weight ratio of one-to-one. They turn at around 60,000 rpm

Also, there is a Russian design of gear reduction that has ratios of around 250:1, with only two or three gears and low friction loss.
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Old 26th May 2004, 03:33
  #33 (permalink)  
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OK Dave, now we know. Your dreams are filled with an electric synchropter with three gears in its 60,000 rpm transmission, and a fiber optic electric cord 200 NM long!

I still see Nichole Kidman when I close my eyes!
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Old 26th May 2004, 05:30
  #34 (permalink)  
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Hi Nick,

I'm sure you agree that electricity will eventually replace fossil fuels. Naturally, this will require significant improvements in the means of producing the electrical energy, storing this energy, and converting this energy to physical motion.

Some of this technology should eventually transfer from mass-produced land vehicles to air vehicles. But, probably no electric synchropter in our lifetimes.

Best that helicopter manufacturers buy the energy storage and conversion devices from outside sources. Hell, you know better than I that helicopter companies could better spend their limited R & D funding on improving the rotor ( excuse me ~ two rotors ).

P.S. If a dream is a type of storage device, like a battery is, would a dream about Nicole Kidman be a wet battery or a dry one?

Last edited by Dave_Jackson; 26th May 2004 at 05:43.
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Old 26th May 2004, 13:18
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The energy technology dreams of the future all rest on "deus ex machina" of fusion reactors, sinced everything else we have tried really doesn't work very well. Actually, nucular fission does work well, but technologists get an F in public relations, so we are in the situation we are in as a result.

Once we get good cheap energy from fusion, it will be the source, and electric distribution will dominate the land side. I think liquid hydrogen gas will serve as the fuel source for transport devices in air and space, since the weight energy density is so good. Fuel cells might get very good, too, but all they would do is re-combine the hydrogen and oxygen that we had split earlier.

Regarding Nichole, she sent me this yesterday:

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Old 26th May 2004, 17:43
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A bit of trivia


You're right about public relations.

France gets 70% of its electrical energy from nuclear plants. They have (maybe no longer) weekly public tours of a shut down facility and also a separate tour an operating facility. Even foreigners could take the tour if they showed their passport.

Good picture.
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Old 26th May 2004, 17:58
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Imagine your electric R22 getting struck by lightning.
Now watch that sucker whizz across the sky.
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Old 6th Sep 2010, 11:55
  #38 (permalink)  
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The future of the helicopter is electric.

I keep banging on about this in other threads for aviation in general. But it makes extra muchness of sense for helicopters. And until batteries are where they need to be, a hybrid solution is very interesting.

Let's toy with the idea for a second.

Brushless motor or motors run the main rotor and anti-torque. You have small battery that can power heli at full power for about 10 minutes. You have turbine APU that runs a brushless gen that recharges the batteries during the flight and/or can directly power the brushless motors. Look at the benefits:

1. No gearbox needed, direct drive on the shaft. Weight savings, reliability improvements.
2. Brushless motors give more power per weight than any other engine (easily about 8-10Kw/kg - beat that gas turbines), which saves weight further.
3. Anti torque is direct driven by a dedicated brushless and rpm only, no complicated shafts, no blade actuation.
4. Brushless motors are pretty much only limited by bearing life, so maintenance should become very cheap.
5. APU gen set can be made cheaper and to lesser standards and be overhauled less frequently because if it should fail, you have 10 minutes on battery power to get safely down.
6. For HEMS and other time critical operations, startup and shutdown would be a 10 second affair. Just power up and go on battery power, then start the APU when you're airborne. That time could save lives.
7. No over temps, no over-torques, no cool downs, no altitude penalties, no shock cooling, no performance losses from tail, no LTE, etc.
8. Much less noisy.
9. Training could be done on batteries alone that get swapped and recharged, which would dramatically lower the cost of training. At least at the home field.
10. Fadecs and governing becomes a piece of cake, as all brushless motors keep the rpm you tell them to keep, regardless of load. That's how you drive them electronically. It's literally a $10 circuit.

I was thrilled to hear about Sikorskys 300CB that they converted to electrics and flew before Oshkosh. It can only fly for 15 minutes at the moment at full power, but it's a great start. Battery capacity has steadily increased over the years and with the new nanowire silicon batteries in development with 10 times more capacity, it could be all over for fossil fueled aviation much quicker than we think. Mind you, I'm no environmental nut, I just welcome all the benefits of electric power. It has virtually no drawbacks and is perfectly suited for aviation.

But let's say one of the big manufacturers presented such a ship tomorrow, the certification processes are not in place. It's going to take FAA and EASA decades before they get on the ball, is my suspicion. That's probably going to be the funnel.

Last edited by AdamFrisch; 6th Sep 2010 at 12:05.
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Old 6th Sep 2010, 13:14
  #39 (permalink)  
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You have small battery that can power heli at full power for about 10 minutes.
Even a R22 according to RHC needs about 60-70kW to maintain level flight at cruise speed. To deliver that for 10 minutes you need at least a 10,000Wh battery - about 200 times the capacity of a big laptop battery, or 20 car batteries. For a R22. 10 minutes.

Thats why the CB300 demonstrator can fly only for 15 minutes.

1. No gearbox needed, direct drive on the shaft. Weight savings, reliability improvements.
2. Brushless motors give more power per weight than any other engine (easily about 8-10Kw/kg - beat that gas turbines), which saves weight further.
Saves weight further? The Gen/Electric Motor/battery are replacing a gearbox, so weight is only saved if they are lighter than the GB.
The turbine is still needed.
Also, what would a brushless motor look like that can deliver, say, 200kW at 400RPM (for main rotor direct drive of a 5 seat helicopter), and would it really be light?
And imagine the battery for THAT.

4. Brushless motors are pretty much only limited by bearing life, so maintenance should become very cheap.
only the gearboxes are replaced in your example, the turbine is still there.

... no altitude penalties, no shock cooling, no performance losses from tail, no LTE, etc.
8. Much less noisy.
Why no altitude penalties? Again, the turbine is still there and required. Same with the noise.

An all electric helicopter would be a great thing for many reasons - but, given the poor energy efficiency of rotary wing flight in general, and the weight problems that come with it, I believe helicopters will be amongst the last vehicles on earth to be succesfully converted to battery power. And that will happen only after some massive breakthroughs in battery technology.
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Old 6th Sep 2010, 13:23
  #40 (permalink)  
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While I agree that an electrically-powered helicopter offers many advantages, and I personally think the hybrid idea is jolly exciting, it is important to remember that most electricity is generated from fossil fuels. Assuming battery technology improves massively, and we can store a useful amount of power in a usable weight, that battery still needs charging - where does that electricity come from? If it's out of the wall socket, ultimately it'll come from fossil fuels.

The other thing to bear in mind (and this is something the current crop of electric cars are running up against) is that you're probably going to need a fair amount of power to run your electric helicopter. Assuming you have somewhere to store said power onboard (whizzy batteries or whatever), you still have to get it in. The capacity of the average household outlet might get you fully charged up in a couple of days, perhaps a week or so - not exactly convenient (endurance of, say, 3 hours per week)! Assuming you have access to a properly meaty supply, and the various connectors and lines to get it to your pad, you're effectively tied to a single base (almost nobody else will have the necessary setup). The hybrid idea is nice, as the necessary infrastructure is already in place, but for fully 'leccy choppers to really take off (ha ha), you need quite a lot of infrastructure upgrade.

Sadly, as much as I'd love to see a proper helicopter based around electric motors, I think there's a bit of a chicken and egg problem here. Any suggestions as to how that can be overcome?
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