Gas Electric hybrid??

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DarylP

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Ok...probably a crazy notion but I have been wondering why a person could not build a plane that was powered by a gas & electric engine. The gas engine would have the power to get you airborne, but then you could shut down the main gas engine for favor of the electric. With all the new technology in solar material coming along all the time, you should be able to make the upper surface of the wings a solar collector. That could help charge a battery and with new lighter battery technology being developed too, it seems that you could have a very energy efficient plane. Of course it would have to be a motor glider I suppose. With an in flight adjustable prop, would that not also help?

Just a thought. What do you all think?
 

autoreply

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Ok...probably a crazy notion but I have been wondering why a person could not build a plane that was powered by a gas & electric engine. The gas engine would have the power to get you airborne, but then you could shut down the main gas engine for favor of the electric. With all the new technology in solar material coming along all the time, you should be able to make the upper surface of the wings a solar collector. That could help charge a battery and with new lighter battery technology being developed too, it seems that you could have a very energy efficient plane. Of course it would have to be a motor glider I suppose. With an in flight adjustable prop, would that not also help?

Just a thought. What do you all think?
The other way around is much better. Gas engines perform terrible at horsepower per pound. Turboprops and electric do much better. So for peak power (T/O) you want electric. Now, for cruise/endurance it's exactly the opposite. Gasoline contains roughly 100 times more energy per pound. So you want gas for range/endurance, not batteries.

Solar panels don't work on real-life aircraft wings. They mess up the flow, can't bend with the wing and output power is way too low, on the order of 50 Watt/m2 (5watt/sqft). Even gliders need much more power to stay aloft.

My bet; 5HP gas engine,100 lbs of batteries and a 100HP electric engine on a normal glider. T/O is spectacular (and reliable), cruise pretty slow but very economic. Think 300 MPG @75 mph, without anything spectacular or even something that doesn't fly yet.
 

rheuschele

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I'm thinking the weight of the battery along with the weight of the fuel would be way too much, even
with today's technology.
 

BBerson

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Autoreply has it right. The same is true for a hybrid automobile, electric is used for boost power (and some regeneration).
If a 5 hp cruise is enough for you, then it makes sense to use Autoreply's design. If you want to cruise with 100hp continuous, then go with gas only.
 

autoreply

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Autoreply has it right. The same is true for a hybrid automobile, electric is used for boost power (and some regeneration).
If a 5 hp cruise is enough for you, then it makes sense to use Autoreply's design. If you want to cruise with 100hp continuous, then go with gas only.
Well, I still hope for someone to put a Rotax/Jabiru in a C182 or a Cirrus. Together with a powerful (200HP) electric engine and enough "juice" for 10 minutes of flight it might be a good safety improvement and give much lower operation cost.

Thatl eads me to another question. How much power does it take to turn an engine that doesn't run anymore?
So say we have an O-200 that delivers 100HP. How much power would you need to turn it at 2500 rpm without ignition or fuel supply, such that you can use the rest of the electric power to turn the prop.
 

roverjohn

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Well, I still hope for someone to put a Rotax/Jabiru in a C182 or a Cirrus. Together with a powerful (200HP) electric engine and enough "juice" for 10 minutes of flight it might be a good safety improvement and give much lower operation cost.

Thatl eads me to another question. How much power does it take to turn an engine that doesn't run anymore?
So say we have an O-200 that delivers 100HP. How much power would you need to turn it at 2500 rpm without ignition or fuel supply, such that you can use the rest of the electric power to turn the prop.
Without some sort of special valve train that would keep the valves closed it would take a lot to operate an IC engine as a pump. Even with it you'd generate a lot of heat and pumping losses. My question is why would you ever have the gas engine shut off? For TO you use both engines and for cruise the electric is shut off so it's freewheeling. In reality it would act as a very underloaded charging system and starter but should not create any greater load than an alternator. I guess I should add that I would put the electric motor directly coupled to the gas.
 
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autoreply

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Without some sort of special valve train that would keep the valves closed it would take a lot to operate an IC engine as a pump. Even with it you'd generate a lot of heat and pumping losses. My question is why would you ever have the gas engine shut off? For TO you use both engines and for cruise the electric is shut off so it's freewheeling. In reality it would act as a very underloaded charging system and starter but should not create any greater load than an alternator. I guess I should add that I would put the electric motor directly coupled to the gas.
If that engine decides to give up on you and quits for whatever reason ;)

Based on my motorcycles compression I'd say 25% of max power. It that a realistic number?
 

roverjohn

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If that engine decides to give up on you and quits for whatever reason ;)

Based on my motorcycles compression I'd say 25% of max power. It that a realistic number?
So are you saying you just would not fly a single engine plane? I ask because unless you're charging the battery pack as you fly along, which would require a much larger gas engine, you wouldn't have any charge to use after TO. Your 25% guess is probably fine but I would maybe guess higher. Still the question as to why the gas motor would ever be turning but not producing power?
 

skeeter_ca

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I would think the best way would to have the prop, electric motor, gas engine in that order. Have some type of clutch system so the motor could run without the engine on or have the engine running and the motor not with the motor acting as an alternator or have both running. That is how the hybrid cars do it. Of course this is a over simplified explanation.
 

autoreply

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So are you saying you just would not fly a single engine plane? I ask because unless you're charging the battery pack as you fly along, which would require a much larger gas engine, you wouldn't have any charge to use after TO.
No, not necessarily. Let's assume we have 40 MJ in electric energy on board. This is equivalent to 80 HP for 11 minutes and would weigh something like 60 kg (135 lbs)
If we have a Cessna 182 with a 100 HP rotax on board we would need the electric assist for about 120 seconds to take-off and climb to 1000 ft. That still gives us 83% of the "reserve" climb. Charging the battery to 100% again takes about half an hour with the heavy generators of for example the de-icing equipment, which are common and proven.
Even the remaining 83% will give you something like a 3000 ft climb, which is normally enough to have a look at your options and prepare for an emergency landing.

Mind you, assuming existing batteries, electric engines (130HP to complement the Rotax) and the Rotax the total weight is still lower as the 6-banger of a C182.
Your 25% guess is probably fine but I would maybe guess higher. Still the question as to why the gas motor would ever be turning but not producing power?
If your engine quits. It gives you the safety of a twin, without extra weight (lower weight in fact), with barely extra complexity and probably lower cost and fuel burn.

Having an electric motor on the crank is about as simple as it gets. Needing a clutch between prop and crankshaft is much more complicated and you can't use existing products.
 
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roverjohn

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No, not necessarily. Let's assume we have 40 MJ in electric energy on board. This is equivalent to 80 HP for 11 minutes and would weigh something like 60 kg (135 lbs)
If we have a Cessna 182 with a 100 HP rotax on board we would need the electric assist for about 120 seconds to take-off and climb to 1000 ft. That still gives us 83% of the "reserve" climb. Charging the battery to 100% again takes about half an hour with the heavy generators of for example the de-icing equipment, which are common and proven.
Even the remaining 83% will give you something like a 3000 ft climb, which is normally enough to have a look at your options and prepare for an emergency landing.

Mind you, assuming existing batteries, electric engines (130HP to complement the Rotax) and the Rotax the total weight is still lower as the 6-banger of a C182.
If your engine quits. It gives you the safety of a twin, without extra weight (lower weight in fact), with barely extra complexity and probably lower cost and fuel burn.

Having an electric motor on the crank is about as simple as it gets. Needing a clutch between prop and crankshaft is much more complicated and you can't use existing products.
What would power your deicing generators while you're trying to maintain climb from 1000'? To charge your batteries from 17% drop in capacity in 10 minutes would require about 25.5 of your available HP assuming that it could be done with near 80% efficiency which I doubt is possible. Can your C182 stay at level cruise at 1000' using only 54.5hp or climb because you think you might have an emergency? I too think Skeeter has the correct order of components but I think the most obvious use would be ground charging your battery pack and then leaving what ever remains in it for emergency use if you use it at all. I would think running the battery dry and gaining as much altitude as possible would be the better approach. Plus let's say your engine fails and locks up, then what good would extra juice in the batteries do you?
 

autoreply

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What would power your deicing generators while you're trying to maintain climb from 1000'? To charge your batteries from 17% drop in capacity in 10 minutes would require about 25.5 of your available HP assuming that it could be done with near 80% efficiency which I doubt is possible. Can your C182 stay at level cruise at 1000' using only 54.5hp or climb because you think you might have an emergency?
The whole merit of the system is that you don't have to charge it that fast. It's an emergency supply, apart from the fact that 83% left over is just fine too, 3000 feet climb is plenty to consider your options and the extra 600 feet is just a nice extra. You can choose to charge it very slowly during a 2 hr cross-country, or rather quickly, when you're descending for landing after 10 minutes.

Ow, and your calculation is incorrect too. You need 15, not 25 hp to charge it in 10 minutes and just 5 to charge it in half an hour. Efficiencies of certified electric engines/generators are above 90%, which would require 16.8 vs 5.5 HP and give you a remaining 83.2 vs 94.5 HP to climb on after you've safely reached 1000 ft. Nothing wrong with a variable charging output either...
Plus let's say your engine fails and locks up, then what good would extra juice in the batteries do you?
Afaik, very few crashes involve a blocked crankshaft. The big majority of engine failures are carb icing, injection/ignition problems and so on. Whether or not to implement an extra component (clutch) is a trade-off, but even the folks with the Rotax (which has one as an option) often prefer to leave it out.

Ground charging has a lot of other problems. You need a power source, converters and the like. The strength of a hybrid is that everything is contained and the same as other aircraft, except for the electric stuff without any penalty and a lot of advantages.
 

Geoffrey Thorpe

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If that engine decides to give up on you and quits for whatever reason ;)

Based on my motorcycles compression I'd say 25% of max power. It that a realistic number?
No. The number will be a lot lower.

With a wide open throttle, pumping will be only a couple percent - you get most of the work from compression back on the expansion at a reasonable engine speed (at low speed ring leakage is big) . Friction would only be a few percent also. I don't have real numbers handy, but I would expect less than 5% of full power.
 

Geoffrey Thorpe

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No. The number will be a lot lower.

With a wide open throttle, pumping will be only a couple percent - you get most of the work from compression back on the expansion at a reasonable engine speed (at low speed ring leakage is big) . Friction would only be a few percent also. I don't have real numbers handy, but I would expect less than 5% of full power.
Ok, I stand corrected. I looked in some references at work - friction would be more on the order of 10% of the max power.
 

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