Pulling power out of the wind

Engineers at GE Power, Atlanta (gepower.com), have updated their 1.5-MW wind turbine, turning it into a 3.6-MW machine specifically built for high-speed wind sites. Its three rotors sweep out 8,495 m2 at between 8.5 and 15.3 rpm. Rotor diameter is 104 m. The turbine can work in winds as low as 3.5 m/sec but cuts out when they top 27 m/sec. It features pitch-controlled rotors and a yaw-controlled nacelle. A hydraulic parking brake holds the blades still in emergencies or for servicing. Electricity comes from a double-fed asynchronous generator that supplies a pulse-width-modulated IGBT-frequency converter. Elastomeric mounts support the generator and gearbox and reduce noise.