Power Regeneration while flying

After a quick look I didn’t find any discussion on this topic, but if I missed it please let me know.

I’m wondering if there is any possibility of having the SP140 prop feed power back into the battery? For example: if the motor is powered off could the prop - assuming it windmills in the air flow - generate power for the battery for inflight recharging?

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This idea crops up from time to time. For cars it makes sense to have a regeneration system because you’re accelerating and decelerating a relatively large mass. You just can’t avoid going and stopping and you’re forced to climb and descend hilly terrain from time to time.

Aircraft are not like that. Flying is, among other things, a continual balance of airspeed and altitude. If you have to much of one you simply use it to generate more of the other. That is your “regeneration”. There’s a pilot axiom - “Speed is life, altitude is insurance”. Why would you want to reduce both at once?

Power is used to overcome drag. Other than air combat or landing a glider, there should never be any reason to add drag. Putting power back into the batteries would require lots of drag. Even if it were as efficient as creating thrust it would just so rarely be used that it would hardly be worth it.

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Very neat. Are you suggesting attaching one to the prop cage? :rofl:

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Thanks for the reply.
While I don’t agree with some of your assertions, I do agree that the key question is would it be worth it?
Since I’ve never flown a para-glider I can’t speak from experience; however, since there are certainly times when descending that drag can be managed and useful. S turns to bleed off altitude for landing are one example. If the prop is windmilling at that point - my assumption - then is driving the motor for regeneration adding significantly more drag? I don’t know.
If a windmilling prop can generate battery power would there be enough to make it worth it? Again, I don’t know.
I’m hoping the designers can share their thoughts.

The amount you could generate would be infinitesimally small. You can stop a windmilling prop with your hand. You are only flying for about 45 minutes and of that, most is spent adding power to maintain altitude. You would gain zero minutes additional flight time.

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A windmilling prop is not generating energy. It uses the energy of the passing wind as altitude decreases only to decrease its own drag, thereby settling at its lowest energy state. Attempting to harness its motion via electromagnetic coupling with the battery in order to reverse the EMF flow as a charge into it will simply stop the prop. Even if the pitch of the prop were controllable to a degree that it could reverse the direction of thrust under power, which without power could trade the energy of aircraft mass motion for another form of energy via autorotation, the combined masses of the aircraft and prop would not be enough mass to perform a function similar to helicopter autorotation or grounded-windmill energy generation. Helicopters only manage the feat marginally with airflow across the rotor-blades that enables them aerodynamically to “glide”, comparable to a fixed-wing aircraft using airflow across the wings to trade altitude for distance in a controlled unpowered descent. But a fixed-wing aircraft would not generate power while using the available altitude potential energy to control its descent, nor would a helicopter autorotate successfully if energy were being siphoned off to charge a battery. There really is no energy to spare as all that is available is used to control the descent, and skill is required even to use that limited quantity to accomplish a successful non-lethal, non-destructive landing. Even sailplanes that may extend a small prop into the slipstream in order to power some few electronic instruments are careful not to increase their drag so much as to slow the aircraft and the relative wind across their wings that generates lift. Aircraft fly because of a balance of forces, and an unpowered aircraft stops flying as soon as its very little stored potential energy becomes exhausted.

Thanks Hans & ProclaimLiberty for your replies.

I guess we’ll have to wait for para gliders to be sewn with solar fabric. The size of the wing should generate enough power to be useful.

Even this would take some almost magical nanotechnology material to work.

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