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wind energy





wind farm
Energy that comes from converting kinetic energy that is present in the wind into more useful forms of energy such as mechanical energy or electricity. Wind energy is a pollution-free, infinitely sustainable form of energy. It doesn't use fuel; it doesn't produce greenhouse gases, and it doesn't produce toxic or radioactive waste.

Windmills that were used to grind grain are an example of early uses of wind energy. Modern uses of wind energy include generation of electricity and pumping water. Current wind energy machines are called wind turbine generators, wind pumps, or more generally, wind turbines.


The history of wind energy

early US windmill
Early in the twentieth century, windmills were commonly used across the Great Plains to pump water and to generate electricity.
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.

Early in the 20th century, windmills were commonly used across the Great Plains to pump water and to generate electricity. 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.

Industrialization, first in Europe and later in America, led to a gradual decline in the use of windmills. The steam engine replaced European water-pumping windmills. In the 1930s, the Rural Electrification Administration's programs brought inexpensive electric power to most rural areas in the United States.

However, industrialization also sparked the development of larger windmills to generate electricity. Commonly called wind turbines, these machines appeared in Denmark as early as 1890. In the 1940s the largest wind turbine of the time began operating on a Vermont hilltop known as Grandpa's Knob. This turbine, rated at 1.25 megawatts in winds of about 30 mph, fed electric power to the local utility network for several months during World War II.

The popularity of using the energy in the wind has always fluctuated with the price of fossil fuels. When fuel prices fell after World War II, interest in wind turbines waned. But when the price of oil skyrocketed in the 1970s, so did worldwide interest in wind turbine generators.

The wind turbine technology R&D that followed the oil embargoes of the 1970s refined old ideas and introduced new ways of converting wind energy into useful power. Many of these approaches have been demonstrated in wind farms or wind power plants – groups of turbines that feed electricity into the utility grid – in the United States and Europe.

Today, the lessons learned from more than a decade of operating wind power plants, along with continuing R&D, have made wind-generated electricity very close in cost to the power from conventional utility generation in some locations. Wind energy is the world's fastest-growing energy source and will power industry, businesses and homes with clean, renewable electricity for many years to come.



The nature of wind energy

Wind energy is the kinetic energy that is present in moving air; this kinetic energy in turn derives from the heating of the atmosphere, earth, and oceans by the sun. The amount of energy in the wind depends mainly on wind speed, but is also affected slightly by the density of the air, which is determined by the air temperature, barometric pressure, and altitude.

For any wind turbine, the power and energy output increases dramatically as the wind speed increases (see wind power profile. Therefore, the most cost-effective wind turbines are located in the windiest areas. Wind speed is affected by the local terrain and increases with height above the ground, so wind turbines are usually mounted on tall towers.


The costs of wind energy

The cost of wind energy is determined by:
• the initial cost of the wind turbine installation
• the interest rate on the money invested
• the amount of energy produced
Any wind turbine that is installed in a very windy area generates less expensive electricity than the same unit installed in a less windy area. So it's important to assess the wind at the potential site.

Modern wind turbine generators cost about $1500 per kilowatt for wind farms that use multiple-unit arrays of large machines. Smaller individual units cost up to $3000 per kilowatt. In good wind areas, the costs of generating electricity range between five and ten cents per kilowatt hour. That cost is somewhat higher than the costs associated with an electrical facility, but wind energy costs are decreasing every year, whereas most conventional generation costs continue to increase.

In remote areas, generating electricity with diesel generators can exceed $0.25 per kilowatt hour. So in good wind areas, electricity that is generated by the wind is clearly cost effective. When compared to the money that is charged by electrical companies, wind energy costs are nearly competitive. And that is without accounting for the environmental and health benefits of using a non-polluting source of energy.


Using wind energy around the world

Worldwide development of wind energy expanded rapidly starting in the early 1990s. In 1999, over $3.5B was invested in farms that use wind energy. Most of the investment was spent in Europe where conventional electricity costs are higher and where political motivation to reduce greenhouse gas pollution is greater. At the end of April 1999, 10,000 megawatts of wind-generated electricity produced some 22.5 TWh of electricity. That is sufficient electricity for all the industrial, commercial and domestic electrical requirements of about two cities the size of Madrid, Spain – a total of about 8 million people.

The average annual growth rate from 1994 to 2001 of the world installed capacity of wind power was 31%, making the wind industry one of the fastest growing. Unlike the last surge in wind power development during 1970s and early 1980s, which was due mainly to the oil embargo of the OPEC countries, the current wave of wind energy development is driven by many forces that make it favorable. These include its tremendous environmental, social, and economic benefits, its technological maturity, the deregulation of electricity markets throughout the world, public support and government incentives. The global wind turbine industry comprises about a dozen major firms located in Europe with annual revenues of about of $100M per year. The Danish wind turbine industry is larger than their fishing and agricultural industries combined.


Benefits of wind energy

Wind energy is an ideal renewable energy because:
• it is a pollution-free, infinitely sustainable form of energy
• it doesn't require fuel
• it doesn't create greenhouse gases
• it doesn't produce toxic or radioactive waste
Wind energy is quiet and doesn't present any significant hazard to birds or other wildlife. When large arrays of wind turbines are installed on farmland, only about 2% of the land area is required for the wind turbines. The rest is available for farming, livestock, and other uses.

Landowners often receive payment for the use of their land, which enhances their income and increases the value of the land. Ownership of wind turbine generators by individuals and the community allows people to participate directly in the preservation of our environment.

Each megawatt-hour of electricity that is generated by wind energy helps to reduce the 0.8 to 0.9 tonnes of greenhouse gas emissions that are produced by coal or diesel fuel generation each year.


Disadvantages

Wind power must compete with conventional generation sources on a cost basis. Depending on how energetic a wind site is, the wind farm may or may not be cost competitive. Even though the cost of wind power has decreased dramatically in the past 10 years, the technology requires a higher initial investment than fossil-fueled generators.

The major challenge to using wind as a source of power is that the wind is intermittent and it does not always blow when electricity is needed. Wind energy cannot be stored (unless batteries are used); and not all winds can be harnessed to meet the timing of electricity demands.

Good wind sites are often located in remote locations, far from cities where the electricity is needed.

Wind resource development may compete with other uses for the land and those alternative uses may be more highly valued than electricity generation.

Although wind power plants have relatively little impact on the environment compared to other conventional power plants, there is some concern over the noise produced by the rotor blades, aesthetic (visual) impacts, and sometimes birds have been killed by flying into the rotors. Most of these problems have been resolved or greatly reduced through technological development or by properly siting wind plants. For more, see wind energy, environmental impact.


Related category

   • WIND POWER