US Patent 7830033 Wind turbine electricity generating system

System for producing electricity from wind energy includes a shaft, at least two turbines rotatably mounted to the shaft and arranged to rotate independent of one another and in opposite directions when subjected to the same wind, and one or more generators that convert rotation of the turbines into electricity. The magnitude of electricity generation by the generator(s) is related to the magnitude of torque induced by the generator(s) on the shaft, and the electricity generation by the generator(s) may be controlled such that torques induced on the shaft by the generator(s) is controlled such that a sum of torques induced on the shaft is substantially zero. Generated electricity is conducted to users, to electricity storage, or to processing components. In an airborne embodiment, a lifting structure generates a lifting force to lift the turbines to a desired altitude, and an anchoring system anchors the turbines relative to the ground.