They have to be tethered, or they won't harvest energy. Free
flying craft don't stand still in the wind without expending
energy, not what you want.
I figured. I suppose that when a hawk hovers, it is in an updraft or thermal.
Still, I do not understand how to calculate the strength of the tether. It seems to me it must be enough to overcome drag only. The Skypower people are talking about building 20 MW units. Obviously a tether could not withstand the force of wind that creates that much energy! The physics are unclear to me, but the wind energy that goes to spin the turbines does not pull on the tether. So what does?
- Jed
