Wind Energy

Wind energy is a form of alternate energy that can be produced by harnessing the power of wind. The wind turbine, the modern-day equivalent of the windmill, is used to capture the wind's power and to generate energy from that power. As a form of energy, wind energy is both renewable (i.e., inexhaustible) and sustainable (i.e., able to be maintained without depleting natural resources). Wind energy's potentially infinite supply is capable of providing power to large populations in areas where wind is plentiful and readily available.

Brief History

Wind energy has been readily available and used as a source of power throughout recorded human history. Ancient peoples, such as the Egyptians, used wind power to move boats from one place to another by capturing the wind in boat sails. Later, windmills were erected and used in China, Persia and the Middle East -- as early as 400 BCE -- to provide irrigation and power for grain mills. These windmills used "sails" made of reed or cloth, which spun horizontally, to produce energy from the wind. Later, windmills used sails that spun vertically to capture wind energy, such as the windmills erected by the Dutch and later throughout Europe and the Far East. This technology was brought to North America by the earliest settlers, as they began to spread across the continent.

Wikipedia's entry "History of Wind Power" has a complete history of the world-wide development of wind power and windmills.

Modern Wind Turbines

Modern wind turbines have replaced windmills in the cultivation of wind to create energy. The modern wind turbine operates on the same principles as early windmills, but is significantly more efficient in harnessing wind power to produce energy. The modern wind turbine consists of a two- or three-bladed propeller-like rotor, which sits atop a very tall tower. The tower stands one hundred or more feet high, to take advantage of the faster winds and lower turbulence present at greater heights.

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Generally speaking, wind turbines convert kinetic energy (the flow of wind) into mechanical energy that can be used to perform specific tasks, or into electricity via a generator that can be used as a source of power. The wind turns the blades of the rotor, which is connected by a shaft to a generator. The shaft spins the generator to create electricity. The U.S. Department of Energy's website provides a animated image of the inside of a wind turbine as well as a working animation to show exactly how wind turbines convert the movement of wind into electricity.

Types of Wind Turbines

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In the United States, most modern wind turbines are found on farms, and take the form of a multi-bladed rotor atop a tall tower shaft attached to a generator. These turbines are similar in form to the older windmill: they operate on a horizontal axis, in which the blades sit on a horizontal axis or axel. Horizontal-axis wind turbines (HAWTs) operate most efficiently in high wind-flow areas and at significant heights, where the wind is most plentiful and steady. HAWTs must face the direction of wind flow: older and smaller versions use a weather-vane design to turn the blades to face the wind, while newer and larger HAWTs use motors to adjust the direction of the blades to face the wind.

HAWTs may be very tall (with some of the tallest reaching 228 feet), especially on large wind farms, but may also be smaller, to be more useful in smaller locations such as small farms and suburban areas. The typical minimum height for a functioning HAWT is 100 feet.

By contrast, vertical-axis wind turbines (VAWTs) are designed so that the blades sit on a vertical axis or axel (such as the Darrieus Wind Turbine and the Savonius wind turbine). VAWTs can operate at lower wind-flow speeds, and therefore at lower heights. Although historically VAWTs were disfavored because of their inefficiency, new designs are ensuring that VAWTs continue to gain popularity: they can be mounted on the roofs of homes, or used in urban areas more efficiently than HAWTs, which makes them perfect for supplying alternative energy in primarily urban and suburban areas.

Advantages and Challenges of Wind Energy

Although wind power is not a new form of alternate energy, it's advantages and challenges lie in renewed interest in this clean, sustainable form of energy.

Among the advantages of using wind energy over other forms of energy:

1. Wind energy is a "clean," non-polluting source of fuel.
2. Wind energy is a good domestic fuel source for countries like the U.S. where wind is abundant.
3. Wind is renewable and inexhaustible, since it is primarily created from the heating of the atmosphere by the sun.
4. Wind energy is one one of the lowest-priced renewable energy technologies available today.
5. Wind energy used on farms can provide benefit tot he economy of rural areas.

There are some challenges inherent in the use of wind energy as a renewable fuel source:

1. Although the cost of wind energy technology has decreased significantly over the last decade, wind energy may have a higher initial cost to implement than fossil-related energy sources.
2. Good wind sites are often located far from cities, where the energy source is needed; transmission lines must be built to carry electricity from wind farms to urban locations. (The National
3. Wind resource development must compete for land space with other highly-valued land uses.
4. Although wind technology has improved, some concerns still exist with regard to blade and rotor noise, aesthetic impact, and damage to wildlife (particularly birds).

Future Benefits

Despite the challenges to wind energy as an alternative energy resource, however, significant benefits still exist. The U.S. Department of Energy predicts that by 2030, if wind energy composes at least 20% of the energy used in the United States:

• More than 15,000 tons of carbon dioxide (greenhouse emissions) will have been avoided by 2050;
• Water consumption in the production of electricity will be reduced by 8% or 4 trillion gallons; and
• Natural gas demand and prices would be reduced, saving consumers approximately $130 billion.

In addition, the manufacture of parts for wind turbines domestically could increase the number of manufacturing jobs available in the United States, while wind farms would beneficially affect the economy of rural areas.

Wind Energy as a Global Resource

Wind energy has significant potential for providing electricity to world nations. An analysis published by the Proceedings of the National Academy of Sciences (PNAS) in July 2009, of the world-wide potential for wind-generated electricity, concludes that "a network of land-based 2.5-megawatt (MW) turbines restricted to nonforested, ice-free, nonurban areas operating at as little as 20%of their rated capacity could supply >40 times current worldwide consumption of electricity, >5 times total global use of energy in all forms."

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In fact, the Global World Energy Council has tracked significant growth in wind energy production world-wide, estimating that 26,240 new wind turbines were installed globally during 2011. This brings the total number of wind turbines installed by the end of 2011 to nearly 200,000, of which nearly 46,000 were located in China alone. China and India stand as the global wind energy powerhouses, as record installations for those two countries account for almost 50% of the installations world-wide in 2011. Although growth was steady in Europe, markets in Central and South America are just beginning to grow their wind energy harvest.

Because of its potential as a cheap source of energy, wind power has the potential for significant growth, especially in third world countries, over the next several years. GWEC and Greenpeace, in their bi-annual report "Global Wind Energy Outlook 2012", estimate that the global wind power market could triple by 2020, provided that governments move quickly to implement favorable policies with regard to wind energy production.

For more information, including a regional analysis of wind energy installation and capacity, see GWEC's website at gwec.net.