Comment Really might be a breakthrough (Score 1) 125
They have been doing demos at small scale, but to really pay out big it needs to be done at much larger scale - as the line drag becomes a smaller and smaller loss the bigger you go and the wind stronger the higher they get. Given that most of their challenges are control system related solving them in small scale means the scale up should be far less risky (flying kites is really really hard compared to aircraft etc due to dominating and unknowable future variance of wind speed and direction)
And if you look at it from a simple cost of materials point of view the systems will be far less than 10% the weight of the turbines they replace, while the wind power flux they can access is several times as high at the altitudes they are aiming at. They are predicting less than half the cost of existing wind energy, but might end up even lower.
Fundamentally there is nothing preventing 10's or even eventually 100's of MW per wing, and its a lot easier to stick out at sea or in other tricky geographical locations than trying to assemble the current huge turbines and their towers.