How Wind Power Works

Wind turbines have blades designed like airplane wings. They rotate due to a pressure differential caused by air moving over the surface of the blade. The blades turn a rotor which drives an electrical generator. Turbines are designed to automatically face the wind either mechanically or by computer-controlled drive systems.

Wind turbines can operate at variable speeds or at fixed speeds. Variable speed designs are more complex but convert wind power into electricity more efficiently. Most new projects use variable speed design.

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

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

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

Controller:   The 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 about 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 1200 to 1500 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 are made from tubular steel (shown here) or steel lattice. Because wind speed increases with height, taller towers enable turbines to capture more energy and generate more electricity.

Wind direction:   This is an "upwind" turbine, so-called because it operates facing into the wind. Other turbines are designed to run "downwind", facing away from the wind.

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

Yaw drive:   Upwind turbines face into the wind; the yaw drive is used to keep the rotor facing into the wind as the wind direction changes. Downwind turbines don't require a yaw drive, the wind blows the rotor downwind.

Yaw motor:  Powers the yaw drive.




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