Hybrid Myth

[Vindication]

I thought it might be good to discuss something that I THINK is a myth. If it isn't and someone with more knowledge of physics can help out than I think that would be great.

Hybrid power plants on aircraft-

I don't think they're any good! I mean in a car the main advantage of a hybrid system is to recapture power that is lost to braking. In other words... store the power from braking electrically and then use it to accelerate the car again.

Now-- planes don't really use brakes (yea I know airbrakes.. but those aren't really used much are they?). I don't see where the regenerative advantage comes in! So hybrid seems useless to me!

Am I missing something here or am I really dispelling a myth?

-Vind

PS BTW an alternator/generator is one thing-- where you use the motor to power your electronics... but having an additional electric motor is another!

[JettPilot]

You are correct. Anytime you create engergy, then convert it and store it somewhere there is a huge loss. Having a gasoline engine to charge a battery and run an electric motor is a huge waste, you are better off to just fly the plane with a small efficient gas engine. The weight of all this stuff is also a huge problem in an airplane, much more so than with a car.

Its not so much the braking that makes hybrid cars efficient, it helps... But mostly the cars benefit in city driving because they charge the batteries while the engine is idling and then shut it off at stop lights etc. The gas engine in the car can now also be smaller than normal and more efficient because the electric motor helps with acceleration. All this is good for a car, but NONE of it helps in an airplane. There is nothing to be gained from a hybrid airplane...

JettPilot

[Unterhausen]

If you want to store energy in an aircraft, gain altitude.

[Tuner]

Their are advantages to this in the fact that a gas system running at a constant RPM that is most efficient for the gas motor.
Gasoline has a much higher energy density that LIPO's Not sure what it is as this is not as straigh forward as with a battery due to combustion inefficiencies...
You can load up a chunk of glow fuel and have the gas generator power the electric motors for 2 hours instead of putting 3 lbs of batteries for a 2hour flight. In the end it is more efficient to still go all gas. However Gas is less reliable so I would you rather have a gas plane engine stall and not be able to restart forcing an emergency landing or would you like a gas motor to stall and it left you with enough onboard batteries to abort and return home. Plus you can stop an electric motor and glide as the gas motor recharges battery.

In my opionion nothing beats a gas motor with electric start. A smart design would use this electric starter for generating electricity for onboard equiptment.

In many senses it is very similar to brakin in a car
1 low power gas motor and fuel charges batteries.
2 plane uses up batteries in climbing to a high altitude
3 plane glides as batteries recharge from small gas motor
4 plane climbs back up using up the batteries and cycle repeats.

[ElectroLawndart]

My thoughts on hybrids is to use the gas motor running a generator powering a brushless motor.

The aircraft would charge the batteries and climb on the generator until the gas motor sputters because of altitude. It would continue climbing on batteries until they run low. Feather the prop and begin a long glide back down to thicker air. Use the generator as a starter for the gas motor and start the process over again.

Hmmmm...sounds kind of Wile E. Coyote when I spell it out that way. Might be fun for a UAV project.

Dart

[JettPilot]

My thoughts on hybrids is to use the gas motor running a generator powering a brushless motor.


That would make an overweight, overly complicated dog of an airplane. You are better off just to use a gas motor that would work at high altitude, or go pure electric and try to get high if thats what you want to do. What you talk about has the weight of the Gas motor, the Generator, AND the batteries, thats about 3 times as heavy as a straight electric or gas... Not to mention that it would be so complicated that you would just be asking for problems. Overall what you propose just sounds like a really bad idea. :mad:

[Hovertime]

Climbing same as acceleration wastes energy.

Use a search, this hybrid was discussed several times before, there is no need to repeat it, also not much interest to do so.
examples:
http://www.rcgroups.com/forums/showpost.php?p=4401017&postcount=67

http://www.rcgroups.com/forums/showpost.php?p=4405706&postcount=79

[kd7ost]

Climbing same as acceleration wastes energy.

Use a search, this hybrid was discussed several times before, there is no need to repeat it, also not much interest to do so.


I don't see anything wrong with guys discussing it. And I believe that there is an interest. That's what these forums are for. Technology is always in flux, now more so that ever. New things are coming along every day. Even though the whole idea is out of the scope of my interest, I enjoy reading about guys idea's. Thread's like this lure in people with different skill sets than those that are just putting camera's on a platform and calling it a UAV. Which by the way I also appreciate. These conversations should all live on as long as someone's interested.

Dan

[clolson]

Climbing same as acceleration wastes energy.

Use a search, this hybrid was discussed several times before, there is no need to repeat it, also not much interest to do so.
examples:
http://www.rcgroups.com/forums/showpost.php?p=4401017&postcount=67

http://www.rcgroups.com/forums/showpost.php?p=4405706&postcount=79

Coming from the open-source software development world, there are times when it is hard to convince someone that their idea is not as well founded as they think it might be. In such cases it is tempting to suggest that they go ahead, build a demo unit, show everyone how well it works, and make believers of us all. That is the most effective way to prove you have a good idea.

It would be hard to tell the Wright brothers they are full of crap while they are flying right over your head ...

Curt.

[Hovertime]

No, of course there is nothing wrong, its actually interesting .

What I meant that repeating same stuff in several threads short time apart is not efficient, and as you see interest is low, gas vs electric thread that had big discussion about hybrids had much more replies and views, while this one mostly stays dormant.

New forum users frequently forget to use a little reSEARCH ;) before posting new ideas about wheels etc;) Otherwise they would see where it was discussed before, read the discussions, possibly joining them there.

If you decide to go ahead and build a demo that is more than welcome by me and will be very interesting to read about! Please keep us updated.

[kd7ost]

No, of course there is nothing wrong, its actually interesting .

What I meant that repeating same stuff in several threads short time apart is not efficient, and as you see interest is low, gas vs electric thread that had big discussion about hybrids had much more replies and views, while this one mostly stays dormant.

New forum users frequently forget to use a little reSEARCH ;) before posting new ideas about wheels etc;) Otherwise they would see where it was discussed before, read the discussions, possibly joining them there.

If you decide to go ahead and build a demo that is more than welcome by me and will be very interesting to read about! Please keep us updated.

I agree but only in part. I mean about the search. Problem is, guys get off topic a lot. It's nice to have threads whose title reflects the content. I don't read all the threads. Some of them I have no interest in so I limit my time in those area's. I have used search and found mention of what I'm looking for in huge long threads where my search is not the main topic. Like the examples you used. "Gas vs Electric" was a thread I started to discuss the pro's and cons of using gas power or electric power in UAV's. So even though I think it was the right place to start talking hybrid, Hybrid actually should have a thread of it's own IMHO. ;)

This for example. Look how far we are off topic from the thread titled "Hybrid Myth".

Dan

[Hovertime]

Exactly ;)

PS little search tip - when you use advanced search option click "show posts" instead of threads, that way it will show posts that are of interest to you. Or find the threads first, then use "search this thread " function.

[kd7ost]

Cool,

Thanks for the tip.

Dan

[ElectroLawndart]

Climbing same as acceleration wastes energy.

Use a search, this hybrid was discussed several times before, there is no need to repeat it, also not much interest to do so.
examples:


Actually the application here is for high altitude. Each part of the drive system being used where it is most effective and efficient. Not for energy conversion within the gas motor's operating altitudes.

Automobile hybrids are effective only in stop and go driving situations where some of the energy of accelleration can be recovered during the dynamic braking period. I guess that a motorglider would be the aircraft equivilant of a automotive hybrid. Climb to altitude and convert altitude to distance, any thermal along the way would be like coasting down a hill.

Horsepower to horsepower, airplanes are way more effective at converting power to distance. I remember a demonstration between a little homebuilt with a 30 HP motor and a 300 HP BMW both going 120 MPH. 30 HP is a little more than half the power of a '67 VW Bug (57 HP).

So yes, I agree. Hybrids for "typical" aircraft application wouldn't make much sense. Just like a car hybrid doesn't make sense for long, constant speed cuising on the highway.

[Hovertime]

Horsepower to horsepower, airplanes are way more effective at converting power to distance. I remember a demonstration between a little homebuilt with a 30 HP motor and a 300 HP BMW both going 120 MPH. 30 HP is a little more than half the power of a '67 VW Bug (57 HP).

Hm... are you sure its was 30 hp homebuilt going 120mph?
Sounds unrealistic sorta.. :confused: .I think that pretty much any airplane would need about 80-100 horses to fly at 120 mph ... Got a link?

I wonder how many of those 300 horses BMW had to utilize to drive 120MPH? About a hundred or so?

[kd7ost]

Clean lines Hovertime. Guys fly 10 pound and smaller glow planes that go near 200 mph on a couple of horses. I have a 22 pound draggy gas powered plane with a Fuji BT32A. ~3.5 horses if I recall. It has landing gear hanging under it and a 102 inch wing span. It will fly 65 mph. These are even poor examples. 35 horses should be no problem in the hands of someone building with clean lines.

Dan

[ElectroLawndart]

Hm... are you sure its was 30 hp homebuilt going 120mph?
Sounds unrealistic sorta.. :confused: .I think that pretty much any airplane would need about 80-100 horses to fly at 120 mph ... Got a link?

I wonder how many of those 300 horses BMW had to utilize to drive 120MPH? About a hundred or so?

Don't have a link for the video of the french homebuilt. But...
The orignal Quickie designed by Burt Rutan had a 22 HP motor and cruised at 120 MPH. Even a Cessna 205 with a 280HP motor cuises(65% throttle) at 160 MPH. I had an old Toyota Supra with an inline 6 that flat out was radared at 122 MPH. That motor put out more than 100 HP at the crank. I don't know how much it put out at the rear wheel. I imagine about 15% less than the crank HP.

Different applications require different solutions. I wouldn't want to run the Quickie on a road race course and I wouldn't expect the BMW to convert gallons of fuel to miles as effiecently.

Dart

[stone_axe]

I'm not aware of hybrid power being used for airplanes.

Hybrid power has been used for decades in locomotives and large ocean vessels because they are more efficient and remove the problematic physical coupling (clutch) of huge power applied to huge mass with much more sturdy electric coupling.

Electric motors are significantly more efficient at accelerating mass from a resting state. Electric motors have maximum torque at 0 rpm and deliver torque consistently throughout their RPM range. This means that electric motors do not need transmissions to accelerate through typical city traffic speeds. That's why the Prius does not use the gas engine around town - except to charge the batteries.

What electric motors lack is the raw power gas engines. That's why they are used as the primary power source, and why a Prius runs the engine for power at highway speeds.

Regenerative braking is a small benefit of a hybrid drivetrain. And since airplanes don't need the torque to accelerate from a stop and cannot afford the weight of batteries I doubt we will see hybrid airplane drivetrains.

[JettPilot]

Coming from the open-source software development world, there are times when it is hard to convince someone that their idea is not as well founded as they think it might be. In such cases it is tempting to suggest that they go ahead, build a demo unit, show everyone how well it works, and make believers of us all. That is the most effective way to prove you have a good idea.

It would be hard to tell the Wright brothers they are full of crap while they are flying right over your head ...

Curt.

Discussing ideas is great... But when someone has such an obviously bad idea, its better to tell him and why. That saves a lost of wasted time and money. If I was trying something that was obviously going to fial, or just plain suck, I would rather know before I had any money and time invested in the project...

[fhhuber506771]

the way the hybrids are done in cars now is a joke anyway... In the mid 1970's VW put out the "Rabbit" Which in diesel version could exceed 60 MPG (real world operation) and the gasolne version exceeded 35 mpg. So how come the "super-efficient" hybrids are proud of 30 mpg?

*******

The reason hybrid in aircraft is essentially useless is the engines are not as far oversize from needed for running at thier most efficient settings when cruising as the car engines are.

It takes about 70% of maximum power from the engine to maintain normal cruise with most aircraft, that also hapens to be at or near the maximum efficiency power for most internal combustion engines.

It takes as little as 15% of maximum power from a car engine for cruising speed on level pavement... The hybrid setup allows a smaller gasoline engine, with the electric to act as a "booster" for acceleration. Then the regenerative braking plus the ability to run on battery only SHOULD allow much higher fuel economy... but its not done for pure evconomy, The modern hybrid is set up for competitive performance with an over-powered gasoline-only vehicle.

************

If you want to REALLY work on fuel economy, hybrids CAN be done more efficiently, but you have to sacrifice some performance. In a 1975 (big heavy) Suburban, you expect 12 to 14 mpg with a 350 ci gasoline engine, you can get 25 mpg using gasoline only... if you stick in a 4 cyl 1.8 liter engine, or about 30 mpg with a current style hybrid... or near 100 mpg if you went to a 25 hp gasoline motor (about equal to 55 mph level road drag) and a 50 hp electric drive hybrid... But the 0-60 acceleration of that last setup (and of the 1.8 liter engine setup) would be about 1 minute.

*********

Power needed to drive a vehicle is directly related to the cube of the speed. We have no real need in the US for the vehicles to be capable of 120 mph when the speed limit is almost always 70 or less.

[stone_axe]

You aren't accounting for the inefficiency of gas engines when having to operate at a broad RPM range under load to function in city traffic. In this scenario the flat torque and broad RPM range of electric motors is MUCH more efficient.

I question getting 14 mpg out of a 1975 Suburban though. A 2005 Suburban is rated at 15 mpg city and 19 mpg highway using the optimistic EPA rating system.

I do agree that the new wave of hybrids are failing to deliver the 55+ mpg in the USA as promised. Their mileage ratings were derived from European and Asian driving styles where city traffic is the norm and inner-city highways are scarce. But the hybrids are getting 40 mpg in practise here, not 30 mpg.

To your point though, my 1985 Nissan Sentra can get over 42 mpg on the highway and routinely gets 38 mpg in mixed driving. (It is interesting to note that the Prius actually gets better mileage in the city than on the highway) So the new hybrids are not delivering anything new or significant or superior to the lowly Japanese cars of the early and mid 1980's.

Power to accelerate a car is directly related to the cube of the weight and is factored by the resistance of its tires. Repetitive acceleration is the bulk of driving. Heavy cars require large tires that create significant rolling resistance.

The Sentra gets its efficiency by being lightweight and having narrow hard tires. The 1985 Sentra is 1,000 lbs lighter than a 2005 Prius and has 80mm narrower tires.

The path to 100 mpg is with lighter cars that require narrower tires, not 3,000 lb cars with fat tires and elaborate drivetrains.

[ElectroLawndart]

The path to 100 mpg is with lighter cars that require narrower tires, not 3,000 lb cars with fat tires and elaborate drivetrains.

I totally agree with you. I wonder if the Ed Begley Jr., Hollywood types had gotten on a different fuel effiency bandwagon where hybrids would be?

Hybrid technology has been around awhile. It was outlawed in Formula One about 10 years ago when the governing body heard that teams were designing electromotive designs like diesel electric locomotives. The teams liked the reliabilty of a IC motor running at a constant RPM and a HUGE electric motor instead of complicated mechanical transmissions.

Dart

[JettPilot]

It was outlawed in Formula One about 10 years ago when the governing body heard that teams were designing electromotive designs like diesel electric locomotives. The teams liked the reliabilty of a IC motor running at a constant RPM and a HUGE electric motor instead of complicated mechanical transmissions.

Dart

What a bunch of idiots. I would love to see stuff like that in Race Cars. When advancements like that work in racing, they find thier way into the real world. Racing is great, but I like to see technology pushed to its limits, not only the drivers. Limiting the cars to old boring technology just takes away alot from racing. In the old days, it was all about making the best car you possibly could and see if it would beat everyone else. Now their only concern is keeping a close race, which is more money dirven and contrary to the spirit of racing....

[fhhuber506771]

To see it in racing, you'd have to get car manufacturers to start sponsoring a new racing class.

Its just a matter of time till that happens... All current racing classes developed from the competitions between experimental cars in the late 1800's/early 1900's, and then production cars after that. NASCAR has its roots in REAL stock, off the factory production line car racing. About the only thing "stock" about a NASCAR car now is the steering column. (and thats debateable...)

[Unterhausen]

The funny thing about nascar is that they are at least 20 years behind the times technologically because they aren't allowed to use computers. I certainly don't blame them for moving away from stock cars: it was simply too dangerous to continue.

The advantage of hybrid cars is simply demonstrated by my commute: in 5 miles, I hit 12 traffic lights, and I feel lucky if I hit a green light 5 times. I don't know if a diesel would help my mileage much, since it has to warm up to perform at peak efficiency. Probably the most efficient car for me is an electric, but of course those are nearly impossible to buy.

Over the last 10 years, the power in most vehicles has gone up astronomically. In 1990, I bought a car that can develop 220 hp, and it was one of the few that would do that. Now it's common to have 240-260hp. Most people use the extra power to cut people off on the interstate and to carry around a lot of extra weight. A new Jetta weighs the same as my '90 Ford Taurus, and is considerably smaller. If they had used the progress in engine technology to increase fuel economy instead, our cars would probably have 30% higher fuel economy. It seems that most cars you can buy run up against the drag polar around 130 mph.

[fhhuber506771]

I read a science fiction story about 20 years ago (I think it was old then) about a nuclear-electric vehicle being entered in a stock car race... one electric motor directly driving each of the 4 wheels. In that story the gas-powered vehicle's drivers of course were doing everything they could to cause the new tech car to crash... but by the end of the race all the racing teams were calling the manufacturer of the new tech vehicle to sign up to buy one...

People resisted changing from the horse and buggy over to the automobile.... There was a lot of (still is some or the Hummer wouldn't sell) resistance to the smaller more economical cars until the gas crisis of the 1970's.. now they are resisting change from the gasoline car to something more appropriate to current civilization.

[DeaninMilwaukee]

It can be remarkable how little power is actually needed with proper aerodynamic design, especially when couped with small frontal area.

That Rutan design used a 22 hp heavy Onan generator engine, and was reputed to do 100 mpg at 100 mph. Not much climb rate, and not room inside for your lunch much less a passenger, but it shows what can be done.

My old motorcycle, a 97 bandit 1200, was far from sleek, and only had 97 rear wheel hp. stock, but was nonetheless radared at 144 mph by the magazines at the time. Small frontal area was why.

I do agree completely about low rolling resistance tires. My 2003 mazda protege has optional 17" high performance tires that have a maximum pressure rating of 50 psi. This car is fairly light, and is a 5 speed, and seems to have almost no rolling resistance at all. If you put it into neutral, it'll coast long distances without slowing much. Obviously, its not needing much power to just maintain speed.

I'm convinced these optional tires are the reason this car gets quite a bit better than its epa estimate of 27-33. I've never seen less than 30 mpg in city driving, and hwy trips have returned numbers as high as 42, although high 30's are more common.

Diesel power could be much better yet. A properly sized small displacement diesel could improve significantly on these number.

A good gas motor will consume about 0.5 lbs fuel/hour per hp at torque peak and full throttle, dropping to around 1 lb/hr per hp at cruising speed loads.

A good diesel will do around 0.33 lbs hr at peak torque rpm/full throttle, but at cruising throttle will still be in the 0.5-0.6 lb range, quite a big difference. Potentially, you could see better than a 50% increase in economy with a diesel, all else being equal.

I'd personally love to see my mazda do 60 mpg. :)


Dean in Milwaukee

[Unterhausen]

I'd personally love to see my mazda do 60 mpg. :)
Dean in MilwaukeeOur pontiac van gets over 100 mpg -- while coasting downhill. That's probably not what you meant. It's amusing to watch the instantaneous fuel consumption sometimes. Starting from a dead stop going up a hill is not one of those times.

I was wondering about the top speed of model aircraft the other day. On another thread, there were a couple of planes mentioned that both topped out below 60. My guess is that the drag polar is still pretty flat at that point, so increasing the hp available would result in a satisfactory increase in top speed.

[clolson]

We had our Rascal 110 clocked (gps) at 102 mph (wind assisted in a slight dive.) That was with an 18x8 prop turning 10,000+ rpm. Well it did 10,000 rpm on the ground, I'm sure higher in the air. The probably translates to about 80-85 mph in still air in the flat. When we put on a Zenoah G26, it probably dropped to about 60 mph top speed. But with a little head wind, we can get the gps pretty close to zero velocity ... so this particular aircraft has a really nice speed range.

Curt.

[ElectroLawndart]

Update...
Just looked on one of the Formula One pages. Guess what! They talking hybrids!
Dart

[ElectroLawndart]

Diesel power could be much better yet. A properly sized small displacement diesel could improve significantly on these number.

A good gas motor will consume about 0.5 lbs fuel/hour per hp at torque peak and full throttle, dropping to around 1 lb/hr per hp at cruising speed loads.

A good diesel will do around 0.33 lbs hr at peak torque rpm/full throttle, but at cruising throttle will still be in the 0.5-0.6 lb range, quite a big difference. Potentially, you could see better than a 50% increase in economy with a diesel, all else being equal.

Dean in Milwaukee

Diesels are WEIRD. A friend of mine spent some 25K$ modifying his Ford diesel pickup truck. Bigger everything,turbo, intake, exhaust, fuel injectors and an engine management computer to control it all. With a 250 HP boost in power he gets better fuel mileage than his stock setup. I don't understand.

Dart

[DeaninMilwaukee]

Diesels are WEIRD. A friend of mine spent some 25K$ modifying his Ford diesel pickup truck. Bigger everything,turbo, intake, exhaust, fuel injectors and an engine management computer to control it all. With a 250 HP boost in power he gets better fuel mileage than his stock setup. I don't understand.

Dart

Not that hard to understand really. He increased its ability to breath which gave it its ability to make better power, but unlike a gas engine that requires a very tightly held air fuel ratio, ie. if a gas motors got more air going through, it also needs a proportunate amount more fuel. A diesel on the other hand can add tons of air to the combustion cycle without adding any more fuel without hurting combustion at all. All that extra air increases compression, and with it, engine efficiency.

I'm guessing his boost kicks in at a lower rpm and is running more of it. BTW, while he's actually using the extra hp he's got, like during towing, it is using more fuel than before, just as you'de expect.

Dean in Milwaukee

[Hovertime]

All I can say is that you are very much misled if you think that hybrid cars are here to save the fuel or help the planet... :rolleyes: They are here to increase company's "green", nature loving image, win more customers, make more $$$ , meet some quotas...

On the other hand DIESELS RULE!!!! :D Visit to Europe or your local VW dealer should be in order;)

[ElectroLawndart]

All I can say is that you are very much misled if you think that hybrid cars are here to save the fuel or help the planet... :rolleyes: They are here to increase company's "green", nature loving image, win more customers, make more $$$ , meet some quotas...

On the other hand DIESELS RULE!!!! :D Visit to Europe or your local VW dealer should be in order;)

Agreed.
Seems like a no-brainer to use the gobs of torque a diesel provides to turn some pretty large gear ratios for highway cruising.

On an interesting side note is flex fuel vehicles. Saab has a turbocharged one that senses what kind of fuel is being burnt. On regular gasoline with it's 87 octane, it's turbo can't boost much for about 97HP. But on high octane ethanol (120, I think), it produces 150 HP.

I think this thread has gone from a debate to discussion for the case that hybrid technology is not the answer, near term or far term.

Dart

[treehog]

The example climbing was probably not the best especialy aas extra weight is not good recipy to climb

also its nessary to understand the total global story

The typical car on the high way at steady 55 mph is probably 12% global effecient 30% global effecient from the motor goes through gearbox blah blah blah and its awful 10 to 12%
on a good day with a following wind and wearing socks instead of shoes................
city driving in europe speeds of 15 mph and that dropps to 5% or less in Rome,Athens.London etc or 7 % in faster flowing amercan urban sprawls

hybid regeneratives pruis etc can restore miserable 5% or 7% to 8 % sometimes
on a good day with a following wind and wearing socks instead of shoes................
12% but at mega bucks to buy the toy
A diesil will give typicaly 50% more mpg per gallon
and so generaly able to match the Prius car size for car size
so a small deisel car will use even less fuel and so tend to be greener
if your not the victim walking on the pavement in Rome
breathing in the carsonagenic soot particales that come out of deisel cars :eek:

Diesel Electric trains work very well due to the fact the top speed for desiel train would be 40mph due to gearing problems of deisel and top speeds of 80mph can be obtained using electric drive train instead
so at certain scale
HYBRIDS WORK

In the model plane the small piston cyclinders using alchol are probably effiency of 5% due to a scale probllem
in that the most effencient size for the piston petrol motor is 250cc to 350 cc or 300cc is best
that explains why pistons are rarely bigger than 350cc and have effiency of 30%

Due the fact the glow motors effency at small size cox 0.49 or 2,5 cc or 5cc will be very very low
and effenciencies will only start at 10cc upward with 4 strokes
there exists a posibilty that in very small sizes
a hybrid might
very small might
have a small edge mostly due to the low effeicecy of small glow motors in a ground static situation
but when you introduce the global affect in the flying situation the extra weight would probably negate this advantage
simple maths double the weight of plane you generaly need double the power to fly

The only situation where there might
again small might
be a possibilty of a hybrid to work might be a high performace EDF turbine using some type of high reving
mayby car motor 2,2hp 3.5cc type
driving a chain of generator and and motor and with a small pack of cells giving 30 seconds eletricmotor run
That type of combo could bypass the ususaul problem of turbine motor in the airflow having to supply revs matched to turbine
and giving a security of 30 seconds eletric motor run in case of glow engine failure and a few seconds extra umphh for take off
It would also reduce the need for big chargers as most times the cells would be topped up and smaller sizes mayby gp1100

In this case the effiencies are awful probably 2%
and provided your pocket could supply the fuel
a possible complicated solution to greatly comlicate an already complicated piture
but could supply slightly longer flying times and a tad more security against the nasty affect dead stick has on deltas
and give some small saving in cell pack sizes and recharging amp requirment and ground supply battery size etc

If it worked it and I use the word if
as the case is very marginal in maths
and when you hook it together there could be other ineffiencies that unexpectanly show up
it might probably be in certian sized jets the 15 cell to 30 cell size be interesting
where below that 10 cells is so simple
and above thirty cells the ram 90 glow or the smaller wrens would maybe easier

Sooner you than me I just limit myself to 10 cells and fly slower the bigger jets

anyway sooner your head banging (neat avtar )on this problem me I figure I will just go straight up to kero jetscat 160 in A FEW YEARS when funds allow

Ralf