[Calimero]

Hi,

As you might know if you've flown a (large) kite before, it can generate a lot of lift. I'd like to exploit this. A kite exerts the least force when it is directly above you, and more and more the closer it is to the ground, and the faster it is traveling.

I'd like to hook up a generator to the kite (via a winch that the line is wound around). It would generate energy (the line would be unwound) when the kite is close to the ground and pulling hard on the line, and reel the line back in when the kite is above you, not pulling so hard.

Question: in the power generating stage, the rpm will be low, and the torque high. What kind of generator has a reasonable efficiency for that? When reeling the line back in, the generator has to act like an electric motor.

There is currently some activity to do this on a large scale, see: http://en.wikipedia....tude_wind_power

Challenges there are to automate the kite's flying, and the high altitude. I'm trying to make something non-automated, and low altitude.

Thank you for reading




From the Wikipedia article:

This post has been edited by Calimero: 26 March 2011 - 11:21 AM

[ewmon]

Calimero, on 26 March 2011 - 11:16 AM, said:

It would generate energy (the line would be unwound) when the kite is close to the ground and pulling hard on the line, and reel the line back in when the kite is above you.

You might want/need to control the "angle of attack" of the kite to the direction of the wind. A high angle to produce lift/power, then a low angle to bring it back down by expending the least amount of power. The low angle is like "feathering" an oar to move it forward for the next stroke.

[Calimero]

ewmon, on 26 March 2011 - 03:43 PM, said:

You might want/need to control the "angle of attack" of the kite to the direction of the wind. A high angle to produce lift/power, then a low angle to bring it back down by expending the least amount of power. The low angle is like "feathering" an oar to move it forward for the next stroke.

Thanks for your reply

Yeah, when the kite is at its apex (directly above you) the angle of attack is lowest, and the kite is stationary, so it doesn't pull as much. That's probably the easiest method to control the angle of attack. A more complicated way would be to use 4 strings, instead of 2.


...I've been trying to understand generators for quite a while, but I'm not technical enough. I think most generators are efficient for high rpm, not low rpm, high torque. And that's what I need here.

This post has been edited by Calimero: 26 March 2011 - 04:07 PM

[SMF]

This scheme seems very complicated. I once saw a proposal to fly large kites up into a jet stream and use the kite as a platform for a wind generator. Because of the large and stable wind speeds this idea appeared to me to have potential. SM

[Calimero]

There are many different options.

I've followed a few of these over the last 5 years, and there are some that are making some progress, while others are not. See the Wikipedia article for more info. One stumbling block is regulation (it's next to impossible to get approval to fly these things at the desired height), another one seems to be to get a working prototype.

I think the one you describe is this: http://www.makanipower.com/# (and video: http://www.ted.com/t...ble_energy.html )


I'd just like to attach a generator to my (large) kite

So, which one should I use?