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Wind Turbines

Wind turbine, like aircraft propeller blades, turn in the moving air and power an electric generator that supplies an electric current. Simply stated, a wind turbine is the opposite of a fan. Instead of using electricity to make wind, like a fan, wind turbines use wind to make electricity. The wind turns the blades, which spin a shaft, which connects to a generator and makes electricity.

How Wind Turbines Work

A wind turbine works the opposite of a fan. Instead of using electricity to make wind, like a fan, wind turbines use wind to make electricity. The wind turns the blades, which spin a shaft, which connects to a generator and makes electricity.

This aerial view of a wind power plant shows how a group of wind turbines can make electricity for the utility grid. The electricity is sent through transmission and distribution lines to homes, businesses, schools, and so on.

Types of Wind Turbines

Wind turbines fall into two basic categories.

1. Horizontal-axis The horizontal-axis variety, like the traditional farm windmills used for pumping water.

2. Vertical-axis The vertical-axis design, like the eggbeater-style Darrieus model.

Most large modern wind turbines are horizontal-axis turbines.Horizontal-axis wind turbines typically either have two or three blades. These three-bladed wind turbines are operated “upwind,” with the blades facing into the wind.

Parts of Wind Turbine

1. Anemometer

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

2. Blades

Most turbines have either two or three blades. Wind blowing over the blades causes the blades to “lift” and rotate.

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

4. 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 55 mph. Turbines do not operate at wind speeds above about 55 mph because they might be damaged by the high winds.

5. 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 1000 to 1800 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.

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

7. High-Speed Shaft Drives the generator.

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

9. Nacelle The nacelle sits atop the tower and contains the gear box, low- and high-speed shafts, generator, controller, and brake. Some nacelles are large enough for a helicopter to land on.

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

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

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

13. 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.

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

15. 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.

16. Yaw Motor Powers the yaw drive.

Turbine Configurations

Wind turbines are often grouped together into a single wind power plant, also known as a wind farm, and generate bulk electrical power. Electricity from these turbines is fed into a utility grid and distributed to customers, just as with conventional power plants.

Wind Turbine Size and Power Ratings

Wind turbines are available in a variety of sizes, and therefore power ratings. The largest machine has blades that span more than the length of a football field, stands 20 building stories high, and produces enough electricity to power 1,400 homes. A small home-sized wind machine has rotors between 8 and 25 feet in diameter and stands upwards of 30 feet and can supply the power needs of an all-electric home or small business. Utility-scale turbines range in size from 50 to 750 kilowatts. Single small turbines, below 50 kilowatts, are used for homes, telecommunications dishes, or water pumping.

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