What we have here is a failure to communicate..
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The designated purpose -IS- to generate electricity for the power grid.
The economics of the situation are such that taking as little out of the grid is a plus.
Using power from the grid to move the kite back to the beginning upwind position is a negative.
Flying the kite back, your "negative alpha" situation, reduces or eliminates the power need to pull/force the kite back to Square 1.
Some power will be needed to wind back the generating tether, but with the kite providing the least amount of drag, by flying a programmed sequence,
the negative penalty is diminished.
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For model testing, get a deep-sea fishing reel with lots of fishing line capacity to simulate the ground based generator and cable drum.
The "drag"wheel on the reel can simulate the power generation portion of the flight sequence, or the power assist added to the reel for the rewind can be used to simulate the actual generator's output, in lieu of the star-drag.
For the rewind situation, run the motor on the reel and measure the power it requires, and test the kite attitudes that need the least amount of power without it plunging to the ground.
And the effects of a long tether on the airframe will be interesting,guaranteed!
