Wind Turbines Today’s wind turbines are very different from the windmills of the past. In the past, windmills were used to grind grain or pump water.Now they convert mechanical power into electricity for homes and businesses.Ranges vary, but it’s is estimated that wind energy could provide approximately 20% to 30% of the energy for America’s homes. Today’s turbines typically begin generating power at wind speeds of 9 miles per hour (mph).However, utility scale wind farms need average wind speeds of at least 14 mph to economically convert wind energy into electricity. As the wind blows, the blades on the wind turbine turn. The blades are connected to a drive shaft that turns an electric generator to produce electricity. On a modern wind farm, this electricity is fed into the local utility grid and distributed to customers just as it is with conventional power plants.
A typical 1 Megawatt turbine will likely have the following characteristics.Note that improvements in technology are changing the design of these towers each year to make them more and more efficient:
Tower Height: 226 feet
Number of Blades:3
Blade Length: 88 feet
Rotor Diameter: 184 feet
Turbine Weight: 208-250 tons
Blades: Glass fiber reinforced epoxy
Tower: Tubular structure
Depending on site conditions, a one megawatt turbine will power approximately 350 average homes.A two megawatt turbine can stand as tall as a 30-story building and cost roughly $3.5-to $4.0 million to install.This size turbine can produce approximately 6 million kilowatts of electricity each year, or enough energy to run 600 average American households.This electricity is sent through transmission and distribution lines to homes, businesses, schools, and consumers who have worked with local energy cooperatives to specifically request Green Energy. The following illustration describes the components of wind turbine in greater detail:
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 55 mph. Turbines do not operate at wind speeds above about 55 mph because they might be damaged by the high winds.
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. 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 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.
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. Rotor: The blades and the hub together are called the rotor. Tower: The towers are made from tubular stee, concrete, or stee lattice. Because wind speed increases with heigh, 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: Measures 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.
To learn more about wind turbines, visit our Links page. Listed you'll find a few of the many major manufacturers.
