Wind energy (Encyclopedia of Environmental Issues, Revised Edition)
Human harnessing of wind energy goes back thousands of years. Historically, people used sails to harness wind energy to propel ships long before the invention of the steam engine. Wind energy has also long been used to drive windmills to grind grain, pump water for irrigation, and keep lands from being flooded with seawater. At the dawn of the twentieth century, however, as fossil fuels became cheap and widely accessible and as the usage and applications of electricity became widespread, windmills began to be neglected except by a few interested researchers and users.
Rapid increases in the prices of fossil fuels during the 1970’s brought a resurgence of interest in wind energy as an alternative source of power. This led to the progressive evolution of windmills into wind turbines—wind-driven machines connected to electrical generators to produce electricity. By the beginning of the twenty-first century, the combination of practical experience, advances in technology, and scientific research had led to the sophisticated wind turbines that dot the landscapes of many countries, including Germany, Denmark, the Netherlands, South Africa, and the United States.
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How Wind Turbines Work (Encyclopedia of Environmental Issues, Revised Edition)
A turbine is a machine that converts the energy that is stored in a moving fluid (such as air, water, or steam) into another form of energy (such as electricity or mechanical work). Wind turbines catch energy from the wind by using blades that are shaped like propellers. The blades are attached to a shaft and are tilted in such a way that the force of the wind on them attempts to lift each blade. The lift is only partially complete, because the shaft begins to turn before the blade rises very high above its original station. This lift effect holds true for each blade, and it is repeated over and over again. The net result is that the shaft rotates continuously as long as the speed of the wind remains above a certain threshold. The assembly consisting of the blades and the shaft to which they are attached is part of what is called the rotor.
During the early days, windmills had six or more blades. It is now known that, by carefully shaping the blades, one can use fewer of them and capture much more energy than windmills did. Thus, in modern times, turbines are equipped with only two or three blades. The wind turbine assembly is mounted onto a tall tower. As a general rule, the taller the tower, the better. This is because the higher above the ground the turbine is located, the less the wind that reaches it is disturbed or reduced by what is on the ground and by surrounding objects such as trees and buildings....
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Applications and Systems (Encyclopedia of Environmental Issues, Revised Edition)
Wind energy applications can be divided into three types: stand-alone wind turbines, distributed energy systems, and turbines that are connected to utility power grids. Stand-alone systems are generally used by home owners and by small business owners—such as ranchers, farmers, and owners of small retail stores—seeking to reduce the size of their electric bills. Others use them for communications and for pumping water. Distributed energy systems are various small power generation technologies that can be grouped and combined for the purpose of improving or expanding the operation and delivery of electrical energy.
For wind turbines to be connected to a local power grid, large numbers of them, generating many megawatts of power, are needed to make the required costs of construction, operation, and maintenance worthwhile. Such arrangements are called wind farms or wind plants. Several providers of electrical power, in the United States and other nations, use wind farms to supply power to their customers.
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Benefits (Encyclopedia of Environmental Issues, Revised Edition)
Research by the American Wind Energy Association indicates that two main categories of benefits are associated with the adoption of wind energy: First, the production of electricity using wind energy reduces environmental risks while enhancing health benefits; and second, the installation of wind farms spurs economic development in the areas, usually rural, where they are located.
The generation of electricity using wind energy produces little air pollution. It is estimated that extensive use of this technology could reduce total U.S. emissions of carbon dioxide, a greenhouse gas associated with global warming, by one-third. This corresponds to a reduction of 4 percent at the world level. Survey data show that forty-six of fifty states in the United States have wind resources that could be developed; thus the potential for growth in this area is very great. For example, if ten of the windiest states in the United States were to develop 10 percent of their wind energy potential, the result would offset the carbon dioxide emissions from all U.S. power plants that burn coal.
The American Wind Energy Association estimated in 2010 that every megawatt of electrical power produced from wind energy generated $1 million in economic development. The association found that when wind energy is adopted by rural communities, local farmers and other landowners receive steady income through the lease of their land and the payment of...
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Further Reading (Encyclopedia of Environmental Issues, Revised Edition)
Burton, Tony, et al. Wind Energy Handbook. New York: John Wiley & Sons, 2001.
Eggleston, David M., and Forrest S. Stoddard. Wind Turbine Engineering Design. New York: Van Nostrand Reinhold, 1987.
Gipe, Paul. Wind Power: Renewable Energy for Home, Farm, and Business. 2d ed. White River Junction, Vt.: Charles Green, 2004.
Hansen, Martin O. L. Aerodynamics of Wind Turbines. 2d ed. Sterling, Va.: Earthscan, 2008.
McKinney, Michael L., Robert M. Schoch, and Logan Yonavjak. “Renewable and Alternative Energy Sources.” In Environmental Science: Systems and Solutions. 4th ed. Sudbury, Mass.: Jones and Bartlett, 2007.
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Background (Encyclopedia of Global Resources)
The energy of the wind was captured by humans as early as the fourth century b.c.e., when the Egyptians used wind to propel sailboats on the Nile River. Soon, there were sailing vessels in the Mediterranean Sea. Windmills, machines that convert wind into mechanical power, were used to pump water and mill grain in ancient times. In a windmill, wind blows on sails or blades radiating from a windshaft (cylindrical part on which the sails turn), which produces mechanical energy when it rotates. The first documented wind device was a Persian windmill shown in drawings from about 500 c.e. This windmill was the horizontal axis type, with a horizontal wheel holding the sails, a vertical windshaft, and vertical sails made of bundles of reeds or wood. These windmills spread throughout the Middle East and into China.
During the twelfth century, the first European windmills appeared in England and France. These wooden machines were called post mills, because they had a central vertical post. They had a horizontal windshaft, had a revolving platform atop the post, and were rotated by hand. In the fourteenth century, a larger and sturdier windmill called the tower mill was developed. The tower mill had a stationary body that supported a rotatable wooden cap, to which the rotor was attached. The blades faced the wind, and there was storage space for the grain at the base. This windmill was popular in Holland, where windmills were used for land...
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Wind Energy Technology (Encyclopedia of Global Resources)
When the Sun warms areas of the Earth at different rates and the various surfaces absorb or reflect the radiation differently, there are differences in air pressure. As hot air rises, cooler air comes in to replace it. Wind, or air in motion, is the result. Air has mass, and moving air contains kinetic energy, the energy of that motion.
Windmills convert wind energy into mechanical power or electricity. The modern electricity windmills are called wind turbines or wind generators. In the wind turbine, wind turns two or three propeller-like rotor blades, which are the sails of the system. When the blades move, energy is transferred to the rotor. The wind shaft is connected to the rotor’s center, so both the rotor and shaft spin. The rotational energy is thus transferred to the shaft, which spins an electrical generator at the other end.
The ability to generate electricity is measured in units of power called watts. A kilowatt represents 1,000 watts, a megawatt is 1 million watts, and a gigawatt represents 1 billion watts. Electricity consumption and production are described in kilowatt-hours. Multiplying the number of kilowatts by the number of hours equals the kilowatt-hours. One kilowatt-hour equals the energy of one kilowatt produced or used for a period of one hour.
The turbine’s size and the speed of the wind through the rotor determine the output of the turbine. As of 2009, the world’s largest...
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Wind Farms (Encyclopedia of Global Resources)
A wind farm or wind power plant is a group of large wind turbines (660 kilowatts and up) installed in the same location to jointly capture wind and produce electricity. There can be up to about one hundred individual modules or turbines sited far apart and covering an extended area of hundreds of square kilometers. Turbines can be added as the need arises. Individual modules connect with a medium-voltage (usually 34.5-kilovolt) power collection system. Then a substation transformer increases the medium voltage of electrical current for connection with a high-voltage transmission system. Wind farms are best located in areas with consistent, strong, and unobstructed winds, such as high plains, mountain passes, and coastlines. In rural, agricultural areas, the land between the turbines can still be used for farming.
As of 2009, the world’s second largest onshore wind farm was Florida Power and Light’s Horse Hollow Wind Energy Center in Taylor and Nolan counties, Texas. Completed in 2006, Horse Hollow has 421 turbines and delivers 735 megawatts of electricity at its peak. The world’s largest wind farm, as of October, 2009, was Roscoe Wind Farm in Texas, designed to deliver 781.5 megawatts from 627 turbines.
In 2008, T. Boone Pickens’s company, Mesa Power, placed a $2 billion order with General Electric (GE) for 667 wind turbines to be delivered in 2010 and 2011. Pickens, the legendary oil executive and energy investor,...
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Advantages and Disadvantages (Encyclopedia of Global Resources)
The first advantage of wind energy is that the fuel is free. The main costs of generating electricity from wind are those of installation, operation, and maintenance. The United States has an abundant supply of wind power that can help promote energy independence from expensive imported energy and thus reduce national economic and security risks. Since 1973, more than $7 trillion has been spent on foreign oil. The wind industry has also created jobs and helped stabilize electricity costs. Since 1980, the cost of wind energy has dropped more than 80 percent.
Wind energy has significant long-term benefits for the environment, human health, and global climate change. Wind is a clean, renewable energy resource that is inexhaustible and easily replenished by nature. Wind power plants do not pollute the air or need waste cleanups like fossil-fuel and nuclear-generation plants, and wind turbines do not emit greenhouse gases or cause acid rain. As of 2009, the wind-energy-generating capacity of the United States was 25,170 megawatts, enough electricity to power almost seven million households. To generate the equivalent of that much energy, 112 million barrels of oil or 31.2 million metric tons of coal (a line of 9-metric-ton trucks more than 22,000 kilometers long) would have to be burned each year.
A significant disadvantage is that wind is inconsistent and intermittent. It is variable power that does not always...
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The Future of Wind Energy (Encyclopedia of Global Resources)
Wind energy is already one of the fastest-growing energy sources, and the market is forecast to expand in the future. Wind power is affordable, readily available, and renewable. Wind energy technology has developed to the point that it can compete successfully with conventional power generation technologies, such as oil, nuclear, coal, and most natural gas-fired generation.
As of 2008, the world’s ten largest producers of wind power were the United States, Germany, Spain, China, India, Italy, France, the United Kingdom, Denmark, and Portugal. There is major wind-energy development globally, and in some countries, wind-power generation has been increasing exponentially. In 2008, in Australia, numerous wind farm projects were approved, and wind power is expected to provide more than 20 percent of the country’s energy by 2020. China has been rapidly increasing its installed wind-power capacity each year since 2005, and estimates predicted that China would achieve a capacity of 100 gigawatts by 2020.
Utility companies have increased investments in wind farms and wind technology. In 2005, General Electric’s turbine business doubled, and by 2009, it was the leading U.S. wind turbine supplier and a world leader, with more than ten thousand wind turbine installations worldwide, comprising more than 15,000 megawatts of capacity. GE operates wind power manufacturing and assembly facilities in Spain, Canada,...
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Further Reading (Encyclopedia of Global Resources)
Baker, T. Lindsay. American Windmills: An Album of Historic Photographs. Norman: University of Oklahoma Press, 2007.
Bartmann, Dan, and Dan Fink. Homebrew Wind Power: A Hands-on Guide to Harnessing the Wind. Masonville, Colo.: Buckville, 2008.
Chiras, Dan, Mick Sagrillo, and Ian Woofenden. Power from the Wind: Achieving Energy Independence. Gabriola Island, B.C.: New Society, 2009.
Craddock, David. Renewable Energy Made Easy: Free Energy from Solar, Wind, Hydropower, and Other Alternative Energy Sources. Ocala, Fla.: Atlantic, 2008.
Evans, Robert L. Fueling Our Future: An Introduction to Sustainable Energy. New York: Cambridge University Press, 2007.
Foster, Robert, ed. Wind Energy: Renewable Energy and the Environment. Boca Raton, Fla.: CRC Press, 2009.
Gillis, Christopher. Wind Power. Atglen, Pa.: Schiffer, 2008.
Gipe, Paul. Wind Energy Basics: A Guide to Home- and Community-Scale Wind-Energy Systems. White River Junction, Vt.: Chelsea Green, 2009.
_______. Wind Energy Comes of Age. New York: Wiley, 1995.
Nelson, Vaughn. Wind Energy: Renewable Energy and the Environment. Boca Raton, Fla.: CRC Press, 2009.
Pickens, T. Boone. The First Billion Is the Hardest: Reflections on a Life of Comebacks and America’s Energy Future. New York: Crown Business, 2008....
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