An aircraft with a parallel hybrid engine has been successfully tested in the UK
phys.org
phys.org
The aircraft they are using for this test looks like it has glider-like wings, which means it requires a lot less thrust to keep aloft, making a low torque and low power electric motor more able to work with it, at the compromise of lower speeds. A more traditional 2-4 seater aircraft capable of 100+ knots would require significantly more power.
The payload capacity of a general aviation aircraft fueled with power-rich gasoline is typically around 500 lbs. Unfortunately, the potential 30% savings in fuel weight (~65 lbs of fuel in a Piper Cherokee) would not be offset by the batteries (using the Prius' 100 lbs of batteries as a reference).
More weight = more power necessary to stay aloft = more power consumption from both the motor and engine.
I hope they can get the technology to work, but there's many more hurdles for a plane than there is for a car; however there have been electrically assisted gliders for some time, so the potential is certainly there.
And it won't be surprising to learn that some militaries already have such systems in use.
Hybrid cars work mainly by recovering energy from braking or going downhill to charge the batteries. Planes don't do that. Where do they recover energy?
I always thought that hybrids were more efficient because you can size the engine to the average power requirement, and not the peak requirement, thereby operating in a more efficient region most of the time, using the battery reserves for when you need peak power. And for some reason I was thinking that operating an engine at a fixed speed allowed for better engineering trade-offs.
While hybrid cars do those things, they aren't the main source of the efficiency of parallel hybrids, parallel hybrids like the Prius work by keeping the engine at the most efficient throttle setting (which is much higher than what would normally be used for cruising) whenever it is running, and using excess power from the engine to recharge the batteries.
The article describes this aircraft as doing the same thing.
It's possible that these requirements lead to engines which have a optimal power output above what would be required in straight & level flight.
This is a reason mathematicians loathe the overuse of "optimal" by engineers: in the real world there are often too much variables.
1. http://en.m.wikipedia.org/wiki/Atkinson_cycle 2. http://www.curbsideclassic.com/blog/the-atkinson-and-miller-...
Parallel hybrids like the Prius, Fusion, etc... do benefit from having something like a CVT, but the biggest gain comes from recovering kinetic energy during braking. Notice that they all get better city mileage than highway! That's because cycles of stop/accelerate have a very low penalty when most of the energy is recovered, so the difference in fuel economy is dominated by drag which is worse at higher speeds.
Hybrid planes and boats make little sense. This one wins by using a smaller engine and supplementing it with an electric motor for takeoff.
Now give me a series hybrid twin-engine aircraft and you've got some possible redundancy/safety improvements, but not much in the way of fuel savings.
"The petrol engine is optimally sized to provide the cruise power at its most efficient operating point, resulting in an improved fuel efficiency overall."
The fact that an airplane's speed and power delivery is much more steady state than a car's is the other big reason this has not been attempted until now.
So, in short, the term "hybrid" makes this a little misleading, since it conjures imagined of the hybrid technology in cars. But this was a hybrid in the sense that an aircraft engine was powered by both a fossil-fuel burning four-stroke engine, and an electric motor in the same flight.
Perhaps one day, though, light enough batteries would allow a fully electric commercial aircraft (though hampered by the lack of an equivalent to regenerative braking), or technologies could be developed to partially charge the batteries using, e.g., air brakes during landing, or solar power.
The truly disruptive if the hybrid means:
- use petro to get to high altitude
- use electric on super high altitude where oxygen is scare
Though still not sure if it is feasible to build such thing, but this thing got huge potential.
Fully electric commercial aircraft are going to need to stretch electric engines as well as battery technology well beyond what they're presently capable of. The video is probably being kind when suggesting it's mere "decades" away.
No, just the battery. Electric motors can reach 96 percent efficiency at the mid to high power levels you need in aircraft. I hit 95 percent for a motor and inverter combined with I was in EV development. It's all battery improvements from here.
Sorry about the late response, but NO. When I wrote that I forgot about power density. Electric motors are currently better than (or comparable to) ICE, but probably not close to a turbine.
Is there work on hybrid or electric passenger flight? Will there be?
[1] Around $200-400m ea for a modern wide-body, according to Boeing's pricing page: http://www.boeing.com/boeing/commercial/prices/
[1]which is why Northwest/Delta were able to get away with running thirsty but long paid-for DC-9s that had been obsolete for nearly a couple of decades until recently.
These days most airlines just break even on ticket sales, but make profits on credit card deals.
Going to a page like this gives you all sorts of scary related stories:
Which is more important in a given application depends of course, but small turbines are terribly inefficient compared to pistons (or even to large turbines), so I wouldn't expect to see your prediction come to pass.
Think of hybrid technology replacing transmissions. You're no longer dependent on mechanical linkage for efficiency. Diesel locomotives have used this advantage for 60+ years (generator runs at optimal speed, tied to electric motors; you'd destroy any transmission with the torque required to pull a freight train).
In a normal plane takeoff is at full power, while cruise is at 75 percent power. So build a smaller engine that can achieve what the big one did at 80 percent and supplement takeoff with the electric motor. Now during cruise you can use the extra 5 percent to recharge the battery. Smaller engine = possibly better efficiency and weight.