Wind has been used as a source of energy for thousands of years. For much of the 20th century, however, it was replaced by coal, gas and oil. Today, though, wind is making a comeback as a source of electricity and power.
In modern times, wind energy is produced with wind turbines. A wind turbine is a tall, tubular tower with blades rotating at the top. When the wind turns the blades, the blades turn a generator and create electricity.
Horizontal-axis wind turbines (HAWTs) are the most familiar type of wind turbine. Most have three large blades. These spin parallel to their towers, where the main rotor and generator are located.
Most HAWTs stand about 61 to 91 meters (200 to 300 feet) tall. Their blades rotate at 10 to 20 rotations a minute.
The enormous, stiff blades on a HAWT usually face the wind. A wind vane or wind sensor first determines which way the wind is blowing. It then turns the turbine to face the oncoming wind.
Vertical-axis wind turbines (VAWTs) have blades that rotate in complete circles around their tower. The main rotor and generator are located near the ground. VAWTs do not have to face the wind to create electricity. They can be much smaller than HAWTs. Often, they are installed on the roofs of buildings.
Turbines cannot operate at every wind speed. If winds are too strong, they can be damaged. Therefore, the turbine has a controller that turns the turbine on when winds are blowing between 13 and 88 kilometers per hour (8 and 55 miles an hour). If the winds become stronger than that, the controller turns the turbine off.
To generate a large amount of electricity, wind turbines are often constructed in large groups called wind farms. Wind farms are made up of hundreds of turbines. These are likely to be spaced out over hundreds of acres.
Wind farms are often located on farmland. In the United States, they are found especially on farmland in Iowa, Nebraska and Kansas.
Wind farms can also be located offshore. These turbines use the stronger winds that develop above the ocean.
Technology is also being developed to create wind farms at very high altitudes. Jet streams are fast-moving winds that blow 9753 meters (32,000 feet) above the Earth's surface. Scientists are designing wind turbines that will be able to turn jet streams' energy into electricity. These turbines will be tied to the ground like a kite, but float thousands of meters in the air.
Wind can be difficult to predict. Both its speed and direction change often. Today, this unpredictability prevents wind power from becoming the main source of energy. However, it can be an excellent addition to traditional power sources.
Windmills And The Evolution Of Wind Energy
Windmills work similarly to wind turbines. In fact, the only difference between windmills and wind turbines is what they are used for. Wind turbines generate electricity. Windmills were originally designed to grind grain and pump water.
In both ancient and modern windmills, a drive shaft connects the blades to two large wheels, or millstones, on the floor of the windmill. The wind rotates the blades. The blades then rotate the drive shaft, and the drive shaft rotates the millstones. Grain is poured into the hollow, rotating millstone and crushed into flour as the wheels grind together. Wind pumps, or water-pumping windmills, operate similarly.
Wind pumps have as many as a dozen rotating blades. Rotation of these blades causes a long rod to move up and down, and the motion of the rod raises and lowers a cylinder. During the down stroke the cylinder fills with water, and during the up stroke, the water is raised to a pipe or well. Wind pumps are still being used all around the world.
In the late 1800s, wind turbines were developed to generate electricity. They were used for that purpose in both Europe and North America.
However, wind energy fell out of favor in the 20th century. Fuels such as coal, oil and natural gas were seen as more reliable sources of electricity and energy. Such fuels create a great deal of pollution, however. By the 1970s, many people had become interested in finding less-polluting sources of energy. The world's first wind farm was established during this time in New Hampshire.
Today, there are wind farms in many parts of the world. The largest one in the United States is the Alta Wind Energy Center in Kern County, California. It has more than 300 turbines.
There are many advantages to using the wind's energy to create electricity.
- Wind cannot be used up.
- Wind is a clean source of energy. Turbines do not pollute the air.
- Wind energy is cheap! In the United States, it costs between 4 cents and 6 cents per kilowatt-hour.
- Wind is found all over the planet. Turbines can be installed almost everywhere.
There are also many challenges in using wind energy:
- Wind energy is cheap to produce once a wind farm has been built. However, the cost to build a wind farm is quite high.
- Wind farms need acres of land. In hilly areas, trees might need to be cut. Many kinds of birds and animals depend on the presence of trees.
- Wind turbines can kill bats and birds.
- Offshore wind farms may damage the ocean ecosystem. To install a wind turbine, the seafloor must be drilled into.
- Some people who live near wind farms complain about the noise. Others say the turbines are ugly.
- Locations that produce great amounts of wind energy are often far away from cities. Transmission lines have to be built to transfer the electricity long distances.
Of course, the biggest problem with wind energy is the wind itself. When the wind is not blowing, electricity cannot be generated.
Anemometers are machines that measure wind speed and direction. They are used to show whether there is enough wind energy at a site to make it a good location for wind turbines.
In the past, most windmills were used to mill grain or pump water. Some also mixed paints and ground oil from things like peanuts or linseed.
land used for, or capable of, producing crops or raising livestock.
layers of gases surrounding a planet or other celestial body.
term for the rapidly developing economies of Brazil, Russia, India and China.
goods carried by a ship, plane, or other vehicle.
a barrier, usually a natural or artificial wall used to regulate water levels.
instrument or tool that transmits the movement of force (torque) to other pieces of connected machinery.
ability used by some animals to emit high-pitched sounds and determine an object's distance by the time it takes for those sounds to echo.
set of physical phenomena associated with the presence and flow of electric charge.
person who plans the building of things, such as structures (construction engineer) or substances (chemical engineer).
flat area alongside a stream or river that is subject to flooding.
coal, oil, or natural gas. Fossil fuels formed from the remains of ancient plants and animals.
machine that converts one type of energy to another, such as mechanical energy to electricity.
animal that feeds on grasses, trees, and shrubs.
gas in the atmosphere, such as carbon dioxide, methane, water vapor, and ozone, that absorbs solar heat reflected by the surface of the Earth, warming the atmosphere.
environment where an organism lives throughout the year or for shorter periods of time.
part of a body of water deep enough for ships to dock.
(horizontal-axis wind turbine) type of windmill where the rotor is arranged horizontally, the main components are in the tower, and the blades rotate when the device faces the wind.
amount of water vapor in the air.
change in economic and social activities, beginning in the 18th century, brought by the replacement of hand tools with machinery and mass production.
winds speeding through the upper atmosphere.
community of living and nonliving things in the ocean.
area of the United States consisting of the following states: Illinois, Indiana, Iowa, Kansas, Michigan, Minnesota, Missouri, Nebraska, North Dakota, Ohio, South Dakota, and Wisconsin.
one of a pair of large, flat, circular stones between which grain or other substances are ground.
energy released by reactions among the nuclei of atoms.
land reclaimed from a body of water by dikes and dams, and used for agriculture, housing, or industry.
network of cables or other devices through which electricity is delivered to consumers. Also called an electrical grid.
Canadian provinces of Alberta, Saskatchewan, and Manitoba. Also called the Prairies.
resource that can replenish itself at a similar rate to its use by people.
to turn around a center point or axis.
part of a machine that rotates around a fixed point (stator).
path in a body of water used for trade.
radiation from the sun.
knowledgeable or complex.
level of Earth's atmosphere, extending from 10 kilometers (6 miles) to 50 kilometers (31 miles) above the surface of the Earth.
to increase or add to.
the science of using tools and complex machines to make human life easier or more profitable.
to tie or fasten an object to something else by a long rope (tether).
powerful light waves that are too short for humans to see, but can penetrate Earth's atmosphere. Ultraviolet is often shortened to UV.
(vertical-axis wind turbine) type of windmill where the rotor is arranged vertically, the main components are at the base, and the blades are parallel to the tower, rotating around it.
movement or circulation of fresh air in a closed environment. Also called air circulation.
movement of air (from a high pressure zone to a low pressure zone) caused by the uneven heating of the Earth by the sun.
kinetic energy produced by the movement of air, able to be converted to mechanical power.
area with a large group of wind turbines, used to generate electric power.
instrument that generates power from the force of wind rotating large blades.
windmill used for pumping water from an aquifer or out of a flooded area.
machine that produces power using the motion of wind to turn blades.