But even these are only using a fraction of the potential. At ground or sea level, the wind is gusty, turbulent, and unpredictable but up in the jet stream, miles above the Earth, the wind is strong, steady, and very predictable. His machine, called a Gyromill, uses the principle of a gyrocopter to provide both lift and power. On the ground, it can be viewed as a simple electric helicopter, with twin counter rotating rotors removing the need for a stabilizing tail plane propeller. Power is fed by cable to the single electric motor, and the machine takes off vertically.
Controls then tilt the machine away from the wind, and the helicopter becomes a kite.
The force of the wind propels the rotors, which provide lift to keep the machine airborne and also generate electrical power by spinning the electric motor. The cable transports the electric current to the ground. There are substantial advantages in both efficiency and power over conventional ground based wind turbines. Roberts estimates a single commercial gyromill would provide twenty megawatts of power, enough for 7000 homes and more than thirty times what a modern standard wind turbine makes. If his calculations are correct, a wind farm of 120 of these machines would provide the same power as Britain s Sizewell B nuclear plant.