I have this idea or a very curious question in my mind. I am no where near professional though, but i would like it to be answered.
It is known how wind turbines can be used to generate electricity. So is it possible to create a quadcopter that will start with some minimal power by small battery but in time will sustain and keep its system on by self generating electricity and keep on rotating its rotors on its own without other external supply?
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http://en.wikipedia.org/wiki/Perpetual_motion
Apparently it is hopeless to try to encourage people to stop smugly ridiculing this poster by constant references to perpetual motion. His question can be read to be asking if wind energy can keep an aircraft aloft. So, let's look at it another way. If you think that only some mistaken belief in perpetual motion can explain this fellows question, then you might also think that a slightly awkward description of a kite would involve some fundamental violations of the laws of physics. How can something just hang up in the sky, indefinitely defying gravity?? "Impossible!", you might proclaim loudly. So who would look ridiculous then?
I might also think you are ridiculous for insinuating that I might hypothetically be ridiculous.
lol,
Seriously though, the OP did not word his question very clearly. As it stands it looks like a question of perpetual motion. Otherwise he might be looking for one of these: GyroKite. They are fun little toys. It would be interesting to see if you could make a multirotor version, and have some control of the individual rotor speeds for stability/control.. Unnecessarily complex, but might be a fun project.
New here, VERY new, but I had to make a comment here. My jest here is that it's not a perpetual machine kind of thing but say if a normal battery lasts one hour before it falls out of the sky he's looking for something that would maybe keep it up for more time. Something that with the weight penalty is still offset to the side of some gain, ie not to much performance hurtiing problems and still gain more time or less weight for the same level of performance. Jerry
Yes Jerome, I think that's the sort of thing he meant.
Bojan, you are correct, it is of course a matter of language since the OP's post is all we have to go on. Also I think English is not his first language. But I take his reference to wind turbines to indicate that he is not meaning a perpetual motion device, but rather that he means to ask if it is possible for a quad to harvest energy on its own to sustain flight.
At the least there is a question there about his meaning. Thus my point remains: Harrumphing, followed by a snap judgement of meaning and an emphatic "Impossible!" is not a correct or useful thing to do.
Regarding your numbered points: Number 1 is addressed above. In Number 2 you use the phrase "wouldn't benefit very much". I totally agree, in fact I think that it would be completely impractical, perhaps enormously expensive, maybe it would have to be very lightweight but also very large (like the human-powered quads), or maybe it would require very exotic rotors, and so on. But "wouldn't benefit much" is certainly not the same as "impossible".
As for the gliding matter, why jump from a fixed wing glider to a rock? I would start with a traditional helicopter rotor system which is quite capable of collecting and storing kinetic energy (used in autorotation). Now don't get me wrong, I'm not proposing that anyone should give more than a glance in such directions. But neither should the term "impossible" be tossed around lightly.
The phrase "it's not possible" has probably made fools out of more people throughout history than any other (with the possible exception of "I do"). It's hardly ever really accurate and it's wisest to leave it out of one's vocabulary.
If someone casually described the technique of Dynamic Soaring without revealing that it is an actual real-world activity, just about everyone would say that it's not possible. How can it be possible to fly in an endless continuous loop and keep gaining more and more energy (translated into higher and higher speeds in current practice)? Ridiculous and counter intuitive! Well, it's not only possible, it's fact and performed routinely. Seeing it is downright spooky, it's so far from what anyone would expect.
So would it really be "impossible" to, say, sense and employ wind-shear regions in a similar way with a multicopter and engage in extracting energy from such flight to then power the aircraft in a normal flight regime until it requires recharging? I'm not talking practical or efficient here, just "possible."
We could certainly fit a tiny wind turbine and generator set into a current Dynamic Soaring aircraft (they look like gliders and another seemingly impossible thing is that they don't just turn into a cloud of dust at 800 kph). That little dynamo could charge a LiPo which then could fly the aircraft outside of the Dynamic Soaring loop. Maybe we could only fly for a short time before needing to re-enter the loop for more charging, but that's beside the point.
So now the "impossibility" has come down to airframe design. Can a rotorcraft in fact extract energy from the wind in such a way? It might be very tricky and horribly inefficient, but who now would still blurt out "Impossible!" without delving into this much more deeply?
QinetiQ a UK based defence contractor has produced a solar powered UAV its basically a flying wing and its huge.
http://www.airforce-technology.com/projects/zephyr/
I agree it would be difficult to replicate it on a multi-copter.
If you could add some solar panels to gain energy plus the wind turbine it might just be possible.... but it requires a lot of work to make it work..
Look at weight/watt produced by solar panel or wind turbine and you will know that it's not possible for mutlicopters. Very efficient glider can use energy from outside, but multicopters are wasting energy as hell: at hover: no speed, constant altitude your potential energy is constant and you need something like 4-10 W/g of energy to stay at this position.
If you make a glider, you just need to find energy to compensate losses from drag forces and therefore you can make some solar powered planes. Have a look to this, but you will see how big is it: Solar Impulse
Regarding turbines, if you have a glider at high altitude and if you need to descend, yes you could get back some energy, but always less that what you spent to reach the initial altitude.
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