Re:An aircraft with a parallel hybrid engine has been succes...
by lutorm on Tuesday December 23, 2014 @03:41PM
(#8790091)
I think focusing on the city mileage is misguided in this case. Yes, hybrids get much better mileage in city driving than non-hybrids, but they also have substantially better highway mileage than non-hybrids. This is exactly because they have a smaller engine that can operate at a more efficient power point during highway cruising. Normal cars are ridiculously overpowered for cruising because they need to be able to accelerate. When the extra power comes from an electric motor, you don't need that. (It's not about the CVT, a non-hybrid can benefit from that, too.)
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.