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Wind Power

Wind is a form of solar energy.

This wind turbine is part of Green Mountain Power's 6 megawatt wind power facility near Searsburg, Vermont. Photo credit: Bob Thresher and DOE/NREL

Winds are caused by the uneven heating of the atmosphere by the sun, the irregularities of the earth's surface, and rotation of the earth. Wind flow patterns are modified by the earth's terrain, bodies of water, and vegetation. Humans use this wind flow, or motion energy, for many purposes: sailing, flying a kite, and even generating electricity.

The terms "wind energy" or "wind power" describe the process by which the wind is used to generate mechanical power or electricity. Wind turbines convert the kinetic energy in the wind into mechanical power. This mechanical power can be used for specific tasks (such as grinding grain or pumping water) or a generator can convert this mechanical power into electricity.

To generate electricity, a wind turbine works the opposite of a motorized 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. The diagram below depicts the components of a typical wind turbine system.



Today, modern wind turbines efficiently convert the force of moving air into electricity using modern design principles and high-tech materials. Wind turbines come in many different sizes from small-scale home systems of 5 kilowatts to 15 kilowatts, to utility scale systems ranging in size from 300 kilowatts to 1,000 kilowatts. To take advantage of higher wind speeds and to allow the blades to rotate without interference, wind turbines are mounted on the top of a tower typically 160 feet high. Although there has been some experimentation with vertical-axis wind turbines, most wind turbines have airfoil-type blades that rotate around a horizontal-axis. The blades are designed like the wing of an airplane creating lift when exposed to the force of the wind, which propels the blades around in a circular motion. The wind turbine rotor typically consists of two or three blades attached to a hub. A rotating shaft from the rotor feeds into a gearbox assembly and then into the generator, which converts the mechanical motion of the shaft into electricity. As the wind changes direction, the yaw system allows the wind turbine to pivot so that the rotor spins in a plane perpendicular to the wind.

Economics and Future Prospects

Wind power is currently very competitive when compared to traditional, fossil-fuel-based energy production technologies. In fact, wind power is the fastest growing energy source around the world. The United States now has a total of 2,600 megawatts of installed wind capacity. This is equivalent to about three or four large coal-fired power plants.

Utility-scale wind farms produce electricity at about 4.5 ¢/kWh which makes wind power competitive with fossil-fuel-generated electricity. It should be noted that these economics are made possible by a federal production tax credit of 1 ¢/kWh. Even though wind is an intermittent resource, meaning wind speeds vary from day to day and month to month, wind power can be easily integrated into the existing supply mix, making a significant contribution to our nation's energy supply. Most analysts agree that technological improvements and economies of scale in wind turbine production will contribute to even further cost reductions in the price of wind-generated electricity.

For Further Information

Visit the following web sites:

• The Energy Efficiency and Renewable Energy Network of the US Department of Energy (www.eren.doe.gov)
• The American Wind Energy Association (www.awea.org)
• The National Renewable Energy Laboratory (www.nrel.gov)