# Is electric propulsion worth it?

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#### danmoser

##### Well-Known Member
In my opinion for electric to be viable with current technology would require use of hydrogen fuel cells which should solve both the problems of range and "recharge times", and if you utilize photovoltaic surfaces and contain the "exhaust" you can use a second smaller cell to reverse the process and potentially extend your distance or allow you to "Recharge" in the sun in the event you have to stop at an airfield without hydrogen service. Capaciter banks can also be used to increase power for take off and climb and allow a smaller power cell for continuous power.
I used to think that too, and fuel cells are likely to become viable eventually .
But they are not today's technology, especially from a homebuilt airplane perspective.
Hydrogen fuel cells are astronomically expensive, and hydrogen storage is VERY difficult.. either heavy tanks for compressed gas, or cryogenic liquid handling equipment minus 420 deg. F.

Hydrogen fuel cell powered planes have flown .. but only govt-funded demo projects.. extremely costly!
As it stands today, Lithium batteries are much cheaper, and likely to stay that way for a good long while.
Other types of fuel cells show promise.. methanol reformer, direct methanol, Aluminum-air, Lithium-Air etc.
But Lithium secondary batteries are still improving and seem likely to be the dominant e-plane power source for at least another decade .. the range limitations will not be solved anytime soon.

#### henryk

##### Well-Known Member
But Lithium secondary batteries are still improving and seem likely to be the dominant e-plane power source for at least another decade .. the range limitations will not be solved anytime soon.
=e-flyers needs big power for take off phase...
-today we have technology for "SINGLE WIRE LINE" electric energy transmission
\f.e. thin,light carbon wire for e-winch of electric motorglider + little battery for home recovery\=

http://www.homebuiltairplanes.com/forums/attachments/aircraft-design-aerodynamics-new-technology/19266d1344584462-revolutionary-emerging-new-technology-imag1131.jpg
http://www.homebuiltairplanes.com/forums/attachments/aircraft-design-aerodynamics-new-technology/19265d1344584460-revolutionary-emerging-new-technology-imag1129.jpg

=from VIESH,Moscow.

#### proppastie

##### Well-Known Member
Log Member
But what about the weight??? For Ultra Lite there are very small and lite 2 stroke gas engines. While the electrics are light and easy starting (nice), but are the batteries? Enlighten us. What are the comparisons?

#### BBerson

##### Light Plane Philosopher
HBA Supporter
But what about the weight??? For Ultra Lite there are very small and lite 2 stroke gas engines. While the electrics are light and easy starting (nice), but are the batteries? Enlighten us. What are the comparisons?
You can probably get the electric system to a similar weight as 2 stroke. But to do that usually requires a small battery and it won't last long with fast discharge. Model airplane guys just buy new batteries.

#### danmoser

##### Well-Known Member
But what about the weight??? For Ultra Lite there are very small and lite 2 stroke gas engines. While the electrics are light and easy starting (nice), but are the batteries? Enlighten us. What are the comparisons?
Actually, the electric motor is lighter than a typical 2-stroke motor of equivalent power..
It's the energy storage mass that favors gasoline in ultralights for over approx. one-hour powered duration..
Below one hour, the electrics have the weight advantage.
Beyond the weight parameter, electric propulsion provides higher reliability, less maintenance, lower vibration/noise, full power availability on demand , and greater high altitude performance.
But if you've got a hard-on for more than one hour of powered flight per take-off, then gasoline's your baby!

#### proppastie

##### Well-Known Member
Log Member
Actually, the electric motor is lighter than a typical 2-stroke motor of equivalent power..
It's the energy storage mass that favors gasoline in ultralights for over approx. one-hour powered duration..
Below one hour, the electrics have the weight advantage.
Beyond the weight parameter, electric propulsion provides higher reliability, less maintenance, lower vibration/noise, full power availability on demand , and greater high altitude performance.
But if you've got a hard-on for more than one hour of powered flight per take-off, then gasoline's your baby!
ok lets get more specific, 2 lb/hp, 1 lb/hp ??? including fuel exhaust pipes etc, or batteries and wire for 1 hr. and is this going to be 10x 5x expensive for electric on initial purchase? I do not expect you to go out of your way here, but perhaps you have done the research and can give a quick answer without much trouble.

#### danmoser

##### Well-Known Member
ok lets get more specific, 2 lb/hp, 1 lb/hp ??? including fuel exhaust pipes etc, or batteries and wire for 1 hr. and is this going to be 10x 5x expensive for electric on initial purchase? I do not expect you to go out of your way here, but perhaps you have done the research and can give a quick answer without much trouble.
My research is limited in scope thus far.
The electric motors have a "peak power" rating that is not comparable to typical 2-strokers.
Peak power is good for 30-60 seconds max. before overheating.. presumably used just during take-off..
Continuous power rating is usually about 70% of peak power rating .. so let's keep it simple and just compare continuous power ratings.

A few data points, submitted for your approval:

Plettenberg Predator 37/6: 14.1hp, 4.3lb, 0.30lb/hp
Plettenberg Predator 50/6: 18.8hp, 5.2lb, 0.28lb/hp
Jobe Motors JM2s: 14.1hp 7.4lb, 0.52lb/hp

These do not include controllers,
batteries, etc.
Compare to 2-stroke engines at 1.5-2.5 lb/hp .. not counting weight of starter, exhaust, etc.

E-motor expense varies widely .. $500 to$2,500 in this power range .. fairly comparable to 2-strokers of equivalent power.

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#### proppastie

##### Well-Known Member
Log Member
well the gas model engine shown no starter required and no fuel is much less than 1 lb/hp and the electrics you talk about do not have battery or controller shown. Admitted the gas and tank for that for an hour and ignition battery is also not shown. So far we are still apples and oranges as regard weight.

#### Topaz

##### Super Moderator
Staff member
Log Member
I'll venture out on a limb here and say that the majority of the advantage for the electric lies in the smoothness, lack of messy/smelly gasoline, and instant-restart capability, rather than specific power output compared to ICE's. It's entirely a matter of convenience and ease/comfort of use, IMHO. For installations like the retractable ones in self-launching sailplanes, there's also no worry about oil coming out of breathers, getting into cylinders, etc., because the engine is being retracted into a 90° different position from running.

They're just cleaner and easier to use. Don't discount that. It can mean a lot to people.

Eventually, with better energy storage, electrics will give more power per weight than ICE motors but, for now, I think the advantages lay in other areas.

#### danmoser

##### Well-Known Member
well the gas model engine shown no starter required and no fuel is much less than 1 lb/hp and the electrics you talk about do not have battery or controller shown. Admitted the gas and tank for that for an hour and ignition battery is also not shown. So far we are still apples and oranges as regard weight.

Well, I agree!
We ARE talking "apples and oranges" here.
Electric propulsion is fundamentally different from gasoline internal combustion engine propulsion.
Weight is an all-important parameter.
With electric power, the engine is light and the energy storage is heavy.
Exactly the opposite is true of gasoline ICE, where the engine is heavy & the energy storage light.
But as Topaz stated, there are other important practical considerations.. reliability, cleanliness, etc.
A deciding factor for me (a motorglider guy living at high elevation) is that gasoline engines vibrate a lot and don't work very well at high altitudes.. which is exactly where I hope to spend most of my powered aviation time.
Get up, find lift, and soar as long, high, and far as possible .. that's what I want to do.. e-power may work great for that.
But we all have different flying machines, aviation goals & preferences.
If you want to fly low and fast for a long time under power.. electric power is not the right choice for you.

Electric airplane people aren't a bunch of enviro-wacko extremists, as some grumpy, stubborn types want you to believe.
There are some practical advantages of e-power, whether you think you are saving the planet's ecosystem for the polar bears, or not.
Electric power is NOT for every pilot and/or every plane.
It depends what you fly and how you want to fly.

#### Aesquire

##### Well-Known Member
I'm pretty grumpy & stubborn, and have contempt for the enviro-whakos,......

But electric makes sense for a motor glider.

I'm waiting for the prices to drop on the batteries. Until then I'm thinking IC.

#### proppastie

##### Well-Known Member
Log Member
which is exactly where I hope to spend most of my powered aviation time.
Get up, find lift, and soar as long, high, and far as possible .. that's what I want to do.. e-power may work great for that.
Could you tell us more as to what you plan, could be similar to many aux power launch glider ultra/lights. How much will your whole package weigh, and what are you planning for duty cycle or duration etc.

#### danmoser

##### Well-Known Member
Could you tell us more as to what you plan, could be similar to many aux power launch glider ultra/lights. How much will your whole package weigh, and what are you planning for duty cycle or duration etc.
Still assessing options & suppliers..
I bought a cheap system to ground test & experiment with..
I'm not sure it is flightworthy stuff at this time, and I won't list the components publicly until it is all proven safe & reliable.
This technology is still very much in its infancy, and there's a lot of crap, phony claims & marketing hype out there .. it'll eventually settle down and we'll have some decent quality, reasonably priced hardware from reputable sources to talk about.

#### Devilkidd1979

##### Active Member
one of the thoughts I was having. IF the electric motors are better for your application, and the batteries are too heavy and expensive, how would a weed eater (or similar) motor running a generator (something like an altenator from a car) stack up for longer flight? Power output of batteries? weight of LIPO packs to gas?
If you have some bench test equipment, you could maybe run some sims and tell us the answers.

#### danmoser

##### Well-Known Member
one of the thoughts I was having. IF the electric motors are better for your application, and the batteries are too heavy and expensive, how would a weed eater (or similar) motor running a generator (something like an altenator from a car) stack up for longer flight? Power output of batteries? weight of LIPO packs to gas?
If you have some bench test equipment, you could maybe run some sims and tell us the answers.
Are you proposing a hybrid gas-electric system with batteries, gasoline motor-generator and electric motor?

#### BJC

##### Well-Known Member
HBA Supporter
how would a weed eater (or similar) motor running a generator (something like an altenator from a car) stack up for longer flight? .
Weed eater engines typically are less than 2 HP, so that wouldn't really help.

#### Topaz

##### Super Moderator
Staff member
Log Member
Are you proposing a hybrid gas-electric system with batteries, gasoline motor-generator and electric motor?
What he's talking about is being done, actually. Basically you can think of this as a "range extender" and that's what I've seen it called. The small IC engine (or, in at least one case, solar panels) are putting charge into the battery pack at the same time the motor is draining it. I assume they're using some kind of sophisticated battery manager to handle the process. I wish I could remember the links where I saw this being done. It's been discussed briefly here on HBA. A search for "range extender" with or without "hybrid" might turn those up.

You still have a net drain over time, but doing this effectively makes the on-power duration longer. It's definitely a stop-gap solution until better batteries come along, but there might be some design missions where the extra range is worth the great deal of added complexity.

#### Devilkidd1979

##### Active Member
What I was considering was using a hybrid system. All drive and thrust performed by electric motor. The Electricity for the motors being made by the much smaller ICE. Since the ICE only has to produce electricity, rather than all the work of driving the aircraft, I think it could be lots smaller and maybe more fuel efficient. Also the electricity would be fed into a bank of capacitors rather than batteries. Same job description, loads less weight. Controls become switches and wires, instead of cables and push pull armatures. You just need someone to put the electric motors on a bench, with the small ICE and generator/altenator and capacitors to see if the required electrical output can be maintained.
Something like this http://youtu.be/wRVVdYU1c0M electric cri-cri
might be able to get longer flight.

#### Topaz

##### Super Moderator
Staff member
Log Member
The issue with that is "power is power". The ICE is still doing all the work - literally, in the exact meaning of the word - of driving the aircraft. And now it has to produce extra power to overcome the losses in the genset, power transmission system, and electric motor.

Let's say your generator is 90% efficient (pulling these numbers out of thin air), your transmission lines are 95% efficient, your motor controller is 85% efficient, and your electric motor is 90% efficient. And let's say you want 100hp (or Watts) of power at the prop.

Your ICE will need to produce: 100/(0.9*0.95*0.85*0.9) = 153 horsepower into the generator to get 100 hp out at the propshaft. Using a genset and remote electric motor makes the ICE engine have to be bigger to account for the losses in the system. It doesn't allow it to be smaller.

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