A wind turbine converts the kinetic energy of moving air into electricity. Wind pushes the blades, which turn a rotor. The rotor spins a shaft connected to a generator. Most modern turbines have three blades, a horizontal axis, and a nacelle that houses the gearbox and generator.

Size has grown dramatically. Early turbines in the 1980s had rotors of 15 meters and produced 50 kilowatts. Today's largest offshore turbines have rotors over 220 meters and produce 15 megawatts. A single rotation of one of these blades can power a home for a day. Taller towers reach stronger, steadier winds.

Turbines operate automatically. Sensors measure wind speed and direction. Motors yaw the nacelle into the wind. Blade pitch adjusts to optimize power or protect the machine in high winds. In storms, the blades feather and the turbine shuts down. Maintenance crews visit a few times a year. Offshore turbines are harder to service, which raises costs.

Key components

• Blades
• Rotor and hub
• Nacelle
• Gearbox and generator
• Tower and foundation