> I do not think those gigantic kites would require
ultra-strong tethers. They would not pull on the
tether much.
This could not be correct, logically.
IF you were right and the kite "would not pull on the
tether much" then you don't need a tehter at all!!
Well, I think it has to overcome drag. That was my impression. But maybe you are right and the machine works like a seagull or hawk that can soar over one spot when the wind is strong enough to generate lift and overcome drag. That would explain why the weight of the tether is not a big issue and the machine can reach high altitudes. It is only needed for the power and control.
Getting back to the autogyro, it is interesting because it can slow down to only 15 mph, which means there is very little energy going into the forward vector. But it cannot stop. To be exact, it *can* stop forward motion, but then it falls gently to the ground, like a falling sycamore pod. This is how an autogyro lands.
An autogyro in a 15 mph headwind can hover over one spot. I heard about a crop duster pilot who could hover a Piper Cub in high winds close to stall speed. He would measure the wind speed by flying into the wind, looking down at the pine trees and slowing down until they stopped moving. Pretty crazy.
Simply divert some of the energy of the windmill into
a propeller giving forward thrust, equal to the "pull"
of the tether (this is easy to figure out), and
convert the rest of the wind energy to microwaves and
beam that energy to diode converters on the ground . . .
Good point. It sounds like a boat sailing into the wind. (Actually, sailboats cannot sail directly into the wind but I suppose a ship was onboard wind turbines could.) But it might be complicated. At least for the initial designs a tether would probably have many advantages because it is a simple way to get the power down to the ground and it would also be good for control electronics and monitoring. And the microwave equipment would be heavy. Plus, it only works in one direction (from aircraft to ground), so you could not power the machine up to make it fly to altitude, or stay at altitude when the winds drops off. (Analogous to when the hawk flaps its wings a few times.)
On the other hand, a tetherless design would be a lot safer for aircraft in the area. The biggest danger for an airplane would be whacking into a tether. WWII barrage balloons were effective because the aircraft risked hitting the cables, not the balloons themselves. When they did hit the cables, it was usually curtains for the airplane. For close-in airfield defense, the British used a rocket that shot up in the air pulling a cable and then deployed a parachute, to keep the cable hanging in the air for a minute or so. It sounds like a nutty Rube Goldberg machine but in 1940 they brought down several German airplanes with them.
Logic dictates that the windmill would need extremely
strong tethers, equal to the strain of the energy
produced - and that is the present drawback.
Yes. The tower acts as a tether. When the wind is blowing it is pushed back and when the wind slows down and propellers are still turning, it is pulled forward. If you feather the propellers they store energy like a gigantic flywheel. It is not efficient but it does smooth over transient changes in windspeed.
- Jed
