• Wind is moving air. Although you can’t see the wind itself, you can see how its force affects things in its path: leaves, grass, flags, laundry on a clothesline — even your hair on a windy day.

    Photo Credit: iStock | istockphoto.com

  • How does wind happen? The sun heats the earth. Then the warm earth heats air next to the ground. The heat makes molecules in the air move more quickly and spread out, which makes hot air rise. When the air cools the molecules slow down and become more dense, so the air sinks to replace the hot, rising air – a movement we know as wind. This heating and cooling process is called convection.

    Photo Credit: airplane: iStock | istockphoto.com

  • Wind Turbine

    The atmosphere has four layers: troposphere, stratosphere, mesosphere, and thermosphere. All the earth’s weather happens in the first layer, the troposphere, which is also the thinnest layer. The space shuttle flies above these layers, and satellites fly higher still.

  • Wind Turbine

    If the earth were an apple, the troposphere would be as thin as the peel. The troposphere (the area closest to the earth, where our weather takes place) is thickest at the equator – about 12 miles above the earth – and thinnest at the poles, where it’s only 4 miles thick.

    Photo Credit: earth: Visible Earth: NASA | visibleearth.nasa.gov/view.php?id=57730
    Photo Credit: apple: iStock | istockphoto.com

  • Wind Turbine

    If the earth were holding still, the hot air above the equator would all rise and get pushed to the poles. There it would cool (because the sun is farther away) and fall as it moved back to the equator to replace the rising hot air. We would have winds that always moved towards the poles at high levels, and towards the equator closer to the ground.

    Photo Credit: earth: Visible Earth: NASA | visibleearth.nasa.gov/view.php?id=57730

  • Wind Turbine

    Because the earth rotates, hot and cold air circulates up and down within three “cells” on each half of the earth. In each cell, the winds often blow from the west or the east. Where the cells meet, there is a river of fast-moving air called the jet stream. There are also smaller cells of air closer to the ground. And it can all move, so the movement of air can be complicated. Near the equator, the earth’s rotation produces very little wind, so it is not a good place for a wind farm.

    Photo Credit: earth: Visible Earth: NASA | visibleearth.nasa.gov/view.php?id=57730

  • Wind Turbine

    This shows the polar jet stream. The red waves show how the jet stream moves and changes over time. Sometimes clouds will follow the path of the jet stream, and make it visible. When the jet stream changes, it affects our weather. It may pull down cold air from the poles, or pull up hot air from the equator areas.

    Photo Credit: NASA Visualization Explorer | svs.gsfc.nasa.gov/vis/a010000/a010900/a010902/
    Photo Credit: Scott Sabol: NASA | www.youtube.com/watch?v=C_HiBj0teRY

  • Wind Turbine

    All our weather happens in the troposphere. Only the troposphere has clouds. Here you can see the top of the troposphere as seen from the space station.

    Photo Credit: NASA Astronaut Photography | eol.jsc.nasa.gov/scripts/sseop/photo.pl?mission=ISS013&roll=E&frame=54329

  • Wind Turbine

    This wind map was created by NASA to show wind patterns in the summer of 1993. The map shows winds at three altitudes. The black arrows show the lowest winds at about 4,900 feet (5,400 meters) high. The white arrows show winds at about 18,000 feet (5,400 meters). The blue arrows show the highest winds at about 30,000 feet (9,200 meters). Look closely. Notice how the winds can blow in different directions at different altitudes. See this map as a movie at NASA or in Cool Links.

    Photo Credit: NASA Visualization Explorer | svs.gsfc.nasa.gov/vis/a010000/a010800/a010856/index.html

  • Wind Turbine

    These are still frames from a fascinating Live Wind Map you can view online at http://hint.fm/wind/. The winds are fastest where the lines are closest together. Just from these four examples, you can see how much wind patterns can change.

    Photo Credit: Live Wind Map | hint.fm/wind/

Wind is moving air. Although you can’t see the wind itself, you can see how its force affects things in its path: leaves, grass, flags, laundry on a clothesline — even your hair on a windy day.
How does wind happen? The sun heats the earth. Then the warm earth heats air next to the ground. The heat makes molecules in the air move more quickly and spread out, which makes hot air rise. When the air cools the molecules slow down and become more dense, so the air sinks to replace the hot, rising air – a movement we know as wind. This heating and cooling process is called convection.
The atmosphere has four layers: troposphere, stratosphere, mesosphere, and thermosphere. All the earth’s weather happens in the first layer, the troposphere, which is also the thinnest layer. The space shuttle flies above these layers, and satellites fly higher still.
If the earth were an apple, the troposphere would be as thin as the peel. The troposphere (the area closest to the earth, where our weather takes place) is thickest at the equator – about 12 miles above the earth – and thinnest at the poles, where it’s only 4 miles thick.
If the earth were holding still, the hot air above the equator would all rise and get pushed to the poles. There it would cool (because the sun is farther away) and fall as it moved back to the equator to replace the rising hot air. We would have winds that always moved towards the poles at high levels, and towards the equator closer to the ground.
Because the earth rotates, hot and cold air circulates up and down within three “cells” on each half of the earth. In each cell, the winds often blow from the west or the east. Where the cells meet, there is a river of fast-moving air called the jet stream. There are also smaller cells of air closer to the ground. And it can all move, so the movement of air can be complicated. Near the equator, the earth’s rotation produces very little wind, so it is not a good place for a wind farm.
This shows the polar jet stream. The red waves show how the jet stream moves and changes over time. Sometimes clouds will follow the path of the jet stream, and make it visible. When the jet stream changes, it affects our weather. It may pull down cold air from the poles, or pull up hot air from the equator areas.
All our weather happens in the troposphere. Only the troposphere has clouds. Here you can see the top of the troposphere as seen from the space station.
This wind map was created by NASA to show wind patterns in the summer of 1993. The map shows winds at three altitudes. The black arrows show the lowest winds at about 4,900 feet (5,400 meters) high. The white arrows show winds at about 18,000 feet (5,400 meters). The blue arrows show the highest winds at about 30,000 feet (9,200 meters). Look closely. Notice how the winds can blow in different directions at different altitudes. See this map as a movie at NASA or in Cool Links.
These are still frames from a fascinating Live Wind Map you can view online at http://hint.fm/wind/. The winds are fastest where the lines are closest together. Just from these four examples, you can see how much wind patterns can change.
Civilizations all over the world have been using wind to power sailboats and sailing ships for more than 5,000 years.
Twenty-two hundred years ago the Chinese used simple windmills to pump water. The Dutch adapted the windmill and used it to drain lakes and marshes. Here in the USA, windmills were used to pump water on farms.
All over the world, in places like Europe, Persia, China, and the Middle East, people used windmills to grind grain. The Romans used windmills, too, to grind grain. And the Pilgrims used windmills to grind corn in the New World.
In the late 1800s, inventors began to experiment with wind and electricity. James Blyth built cloth sails on a windmill to generate electricity for his vacation cottage in Scotland. In Cleveland, Ohio, Charles Brush built a large turbine on a 60 foot (18 meters) tower. The turbine had 144 blades. It could generate 12 kilowatts of electricity to charge batteries, or power up to 100 light bulbs.
This is a wind farm. Its turbines turn with the wind as it blows. They are connected by underground wires. If one stops working, the others will still turn, producing electricity day and night, as long as the wind is blowing. A wind farm like this one could have more than 100 wind turbines, and create power for thousands of homes.
Wind farms are not always built on farmland. They could be built in the mountains, where they can catch the winds up high.
Wind farms can also be built in the desert. Here the land is usually flat and open, with lots of wind.
These windmills off the shore of Denmark near Copenhagen tower over that sailboat on the right. Except for the area near the equator, winds move well over the ocean and there is plenty of wide open space for wind farms.
As you can see by these single turbines, individual farms, homes or businesses can also use wind power.
Future wind farms may look very different from the turbines we see in farm fields. These designs show a few of the exciting new ways that engineers are working to capture the wind.
Where to put a wind farm? Where there’s wind!
Some parts of the United States are more windy than others. Wide open, flat areas with few trees are often good sites for wind farms. In some places, there are also windy places on the water along the coast.
Why do some areas have many wind farms, while areas have none? Because of their geography, some states are well-suited to generate electricity from wind.
This flattened globe shows the variation of wind speed over all the continents and oceans. Generally the winds over the ocean are more than twice as fast as they are over land.
This wind farm far from the city takes advantage of strong winds and open space.
When a new wind farm is being considered, engineers study the location first to see if it will be a good place to put a wind farm.
Before spending money to build an entire wind farm, engineers often put up temporary equipment to test the speed and direction of the wind at that location. Here you can see a tall “met” tower (meteorological tower) being put up. It has instruments and gauges high up in the air to test the wind.
Neighbors who live near the proposed wind farm are invited to community meetings to learn about the project and give their opinion.
Many places that have a lot of wind do not have transmission lines. That’s a problem because if there is no way to feed wind power into the energy grid, it cannot be used.
Utilities try to locate wind farms away from areas where great numbers of birds or bats migrate to help prevent collisions and injuries.