Wind turbine glossary

Anemometer Measures the wind speed and transmits wind speed data to the controller.

Blades Most turbines have two or three blades. Wind blowing over the blades causes them to "lift" and rotate.

Brake A disc brake that can be applied mechanically, electrically or hydraulically to stop the rotor in emergencies.

Controller Starts up the machine at wind speeds of about 8 to 16 miles per hour (mph) and shuts off the machine at about 65 mph. Turbines cannot operate at wind speeds above 65 mph because their generators could overheat.

Gear box Gears connect the low-speed shaft to the high-speed shaft and increase the rotational speeds from about 30 to 60 rotations per minute (rpm) to about 1,200 to
1,500 rpm — the rotational speed required by most generators to produce electricity. The gear box is a costly (and heavy) part of the wind turbine and engineers are exploring "direct-drive" generators that operate at lower rotational speeds and don't need gear boxes.

Generator Usually an off-the-shelf induction generator that produces 60-cycle AC electricity.

High-speed shaft Drives the generator.

Low-speed shaft The rotor turns the low-speed shaft at about 30 to 60 rotations per minute.

Nacelle The rotor attaches to the nacelle, which sits atop the tower and includes the gear box, low- and high-speed shafts, generator, controller and brake. A cover protects the components inside the nacelle. Some nacelles are large enough for a technician to stand inside while working.

Pitch Blades are turned, or pitched, out of the wind to keep the rotor from turning in winds that are too high or too low to produce electricity.

Rotor The blades and the hub together are called the rotor.

Tower Towers can be made from tubular steel or steel lattice. Because wind speed increases with height, taller towers enable turbines to capture more energy and generate more electricity.

Wind direction "Upwind" turbines are designed to operate facing into the wind. Other turbines are designed to run "downwind," facing away from the wind.

Wind vane Measures wind direction and communicates with the yaw drive to orient the turbine properly with respect to the wind.

Yaw drive Keeps the rotor of upwind turbines facing into the wind as the wind direction changes. Downwind turbines don't require a yaw drive because the wind blows the rotor downwind.

Yaw motor Powers the yaw drive.

Source: U.S. Department of Energy