Wind HeaderTable of Contents

  1. What is wind energy?
  2. How do wind mills work?
  3. What is the history of wind energy?
  4. Where is wind energy produced?
  5. What are the advantages of wind energy?
  6. What are the disadvantages of wind energy?
  7. Data
    • Generation
    • Capacity




1.  What is wind energy?


Wind is air in motion.  The disparate heating rates of different surfaces on the earth create wind.  For example, land heats faster than water.  This means that the air above land heats, expands, and rises faster than the air above water.  When this happens, cooler air rushes in to its place, creating wind.    This is called the daily wind cycle. The opposite occurs at night since air cools more rapidly over land as well, causing the winds to reverse.  On a global stage this same general phenomenon occurs when air is heated at the Earth’s equator, causing the atmospheric winds that circle the earth.

By using the wind to turn the blades of a wind mill, people can generate electricity.

Wind Cycle



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2.  How do wind mills work?

Wind Mill

Horizontal-axis turbines

Most wind machines used today are the horizontal-axis type. Horizontal-axis wind machines have blades like airplane propellers. A typical horizontal wind machine stands as tall as a 20-story building and has three blades that span 200 feet across. The largest wind machines in the world have blades longer than a football field.

Vertical-axis turbines

Vertical-axis wind machines have blades that go from top to bottom. The most common type — the Darrieus wind turbine, named after the French engineer Georges Darrieus who patented the design in 1931 — looks like a giant, two-bladed egg beater. This type of vertical wind machine typically stands 100 feet tall and 50 feet wide. Vertical-axis wind machines make up only a very small share of the wind machines used today.

Wind power plants produce electricity

Wind power plants, or wind farms, as they are sometimes called, are clusters of wind machines used to produce electricity. A wind farm usually has dozens of wind machines scattered over a large area. The world’s largest wind farm, the Horse Hollow Wind Energy Center in Texas, has 421 wind turbines that generate enough electricity to power 220,000 homes per year.

Many wind plants are not owned by public utility companies. Instead, they are owned and operated by business people who sell the electricity produced on the wind farm to electric utilities. These private companies are known as Independent Power Producers.


3.  What is the history of wind energy?


Since early recorded history, people have been harnessing the energy of the wind. Wind energy propelled boats along the Nile River as early as 5000 B.C. By 200 B.C., simple windmills in China were pumping water, while vertical-axis windmills with woven reed sails were grinding grain in Persia and the Middle East.

New ways of using the energy of the wind eventually spread around the world. By the 11th century, people in the Middle East were using windmills extensively for food production; returning merchants and crusaders carried this idea back to Europe. The Dutch refined the windmill and adapted it for draining lakes and marshes in the Rhine River Delta. When settlers took this technology to the New World in the late 19th century, they began using windmills to pump water for farms and ranches, and later, to generate electricity for homes and industry.

American colonists used windmills to grind wheat and corn, to pump water, and to cut wood at sawmills. As late as the 1920s, Americans used small windmills to generate electricity in rural areas without electric service. When power lines began to transport electricity to rural areas in the 1930s, local windmills were used less and less, though they can still be seen on some Western ranches.

The oil shortages of the 1970s changed the energy picture for the country and the world. It created an interest in alternative energy sources, paving the way for the re-entry of the windmill to generate electricity. In the early 1980s, wind energy really took off in California, partly because of state policies that encouraged renewable energy sources.

In the 1970s, oil shortages pushed the development of alternative energy sources. In the 1990s, the push came from a re-newed concern for the environment in response to scientific studies indicating potential changes to the global climate if the use of fossil fuels continues to increase. Wind energy is an economical power resource in many areas of the country.

Growing concern about emissions from fossil fuel generation, increased government support, and higher costs for fossil fuels (especially natural gas and coal) have helped wind power capacity in the United States grow substantially over the past 10 years.




4.  Where is wind energy produced?

Capacity Map

Note: See progress of installed wind capacity between 1999 and 2012

In 2012, wind turbines in the United States generated about 3% of total U.S. electricity generation. Although this is a small share of the country’s total electricity production, it was equal to the annual electricity use of about 12 million households.

The amount of electricity generated from wind has grown significantly in recent years. Generation from wind in the United States increased from about 6 billion kilowatthours in 2000 to about 140 billion kilowatthours in 2012.

New technologies have decreased the cost of producing electricity from wind, and growth in wind power has been encouraged by tax breaks for renewable energy and green pricing programs. Many utilities around the country offer green pricing options that allow customers the choice to pay more for electricity that comes from renewable sources to support new technologies.

International Wind Power

In 2009, most of the wind power plants in the world were located in Europe and in the United States where government programs have helped support wind power development. The United States ranked first in the world in wind power generation, followed by Germany, Spain, China, and India. Denmark ranked ninth in the world in wind power generation, but generated about 19% of its electricity from wind, the largest share of any country.

Offshore Wind Power

Conditions are well suited along much of the coasts of the United States to use wind energy. However, there are people who oppose putting turbines just offshore, near the coastlines, because they think the wind turbines will spoil the view of the ocean. There is a plan to build an offshore wind plant off the coast of Cape Cod, Massachusetts (the project is called Cape Wind).

Wind is a renewable energy source that does not pollute, so some people see it as a good alternative to fossil fuels.

There are two types of wind machines (turbines) used today, based on the direction of the rotating shaft (axis): horizontal-axis wind machines and vertical-axis wind machines. The size of wind machines varies widely. Small turbines used to power a single home or business may have a capacity of less than 100 kilowatts. Some large commercial-sized turbines may have a capacity of 5 million watts, or 5 megawatts. Larger turbines are often grouped together into wind farms that provide power to the electrical grid.


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5.  What are the advantages of wind energy?

Wind farm

Wind is a clean source of energy, and overall, the use of wind for energy has fewer environmental impacts than using many other energy sources. Wind turbines (often called windmills) do not release emissions that pollute the air or water (with rare exceptions), and they do not require water for cooling. They may also reduce the amount of electricity generated from fossil fuels and therefore reduce the amount of air pollution, carbon dioxide emissions, and water use of fossil fuel power plants.

A wind turbine has a small physical footprint relative to the amount of electricity it can produce. Many wind projects, sometimes called wind farms, are located on farm, grazing, and forest land. The extra income from the turbines may allow farmers and ranchers to stay in business and keep their property from being developed for other uses. For example, wind power projects have been proposed as alternatives to mountain top removal coal mining projects in the Appalachian mountains of the United States. Offshore wind turbines on lakes or the ocean may have smaller environmental impacts than turbines on land.


6.  What are the disadvantages of wind energy?


Wind turbines do have negative impacts on the environment, but the negative impacts have to be balanced with our need for electricity and the overall lower environmental impact of using wind for energy relative to other sources of energy to make electricity.

Modern wind turbines are very large machines, and some people do not like their visual impact on the landscape. A few wind turbines have caught on fire, and some have leaked lubricating fluids, though this is relatively rare. Some people do not like the sound that wind turbine blades make. Some types of wind turbines and wind projects cause bird and bat deaths. These deaths may contribute to declines in species that are also being affected by other human-related impacts. Many birds are killed from collisions with vehicles and buildings, by house cats and hunters, and by pesticides. Their natural habitats may be altered or destroyed by human development and by the changes in the climate that most scientists believe are caused by greenhouse gases emissions from human activities (which wind energy use can help reduce). The wind energy industry and the U.S. government are researching ways to reduce the impact of wind turbines on birds and bats.

Most wind power projects on land also require service roads that add to their physical impact on the environment. Making the metals and other materials in wind turbines and the concrete for their foundations requires the use of energy, which may be from fossil fuels. Some studies have shown that wind turbines produce much more clean electricity over their operating life than the equivalent amount of energy used to make and install them.


7.  Data


  • Generation

Generation - World - Graph

Generation - Country - Graph

Generation - Table


  • Capacity

Capacity - World - Graph

Capacity - Country - Graph

Capacity - Table



**The information on this website was obtained from various pages of the U.S. Department of Energy website ( and the U.S. Environmental Protection Agency website (  The data on this website was obtained from various pages of the U.S. Energy Information Administration website (  Please consult those websites for further information.