While I'm sure they will face many challenges, what they are doing is not the equivalent of putting a ground based turbine in the air. Their "wing" is the equi

While I'm sure they will face many challenges, what they are doing is not the equivalent of putting a ground based turbine in the air. Their "wing" is the equivalent to a part of a turbine blade, and it moves in circles like a turbine blade would. The propellors in the wing are what extract the energy, but they would not be nearly as big as the blades on a conventional wind turbine.