Wind energy is the leading source of renewable electricity.

Wind power is the conversion of wind energy into a useful form, such as electricity, using wind turbines.  Wind energy is actually a converted form of solar energy.

The sun's radiation heats different parts of the earth at different rates-most notably during the day and night, but also when different surfaces (for example, water and land) absorb or reflect sunlight at different rates. This in turn causes portions of the atmosphere to warm differently. Hot air rises, reducing the atmospheric pressure at the earth's surface, and cooler air is drawn in to replace it. The result is wind.  Air has mass, and when it is in motion, it contains the energy of that motion ("kinetic energy").

Wind energy systems transform the kinetic energy of moving air (wind) into mechanical or electrical energy that can be harnessed for practical use.

Humans have used wind power for at least 5,500 years to propel sailing ships, and architects have used wind-driven natural ventilation techniques in buildings since similarly ancient times.  In recent centuries, humans have converted wind into mechanical energy for pumping water or grinding grain (the "farm windmill" is still seen in many rural areas of the U.S. and Europe), but the principal application of wind power today is the generation of electricity.

The first modern wind turbines were built in the early 1980s, and today there are over 100,000 wind turbines installed in 70 countries.  Wind power currently supplies the electricity needs of more than 25 million households.

How Does Wind Power Work?

Wind turbines catch the wind's energy with their propeller-like blades.

Usually, two or three blades are mounted on a shaft to form a rotor. A blade acts much like an airplane wing. When the wind blows, a pocket of low-pressure air forms on the downwind side of the blade. The low-pressure air pocket then pulls the blade toward it, causing the rotor to turn. This is called lift. The force of the lift is actually much stronger than the wind's force against the front side of the blade, which is called drag. The combination of lift and drag causes the rotor to spin like a propeller, and the turning shaft spins a generator to make electricity.

Wind turbine towers are mostly made of steel, while the blades are made of fiberglass-reinforced polyester or wood-epoxy.  Turbines come in various sizes, and turbine technology is developing rapidly.

There are two basic designs of wind turbines used to produce electricity: vertical-axis, or "egg-beater" style, and horizontal-axis (propeller-style) machines. Horizontal-axis wind turbines are most common today, accounting for nearly all of the "utility-scale" (100kW capacity and larger) turbines operating globally.

(Graphic: http://www.awea.org/faq/wwt_basics.html)

Wind turbines generate electricity for homes, schools and businesses, and excess electricity not consumed at the source is often sold to utilities for cash or credit toward future electricity consumption.

Large-scale wind farms are typically connected to the local electric power transmission network. Smaller turbines are also used to provide electricity to isolated “off-grid” locations such as remote homes, water pumps and communications equipment.  

Offshore Wind Farms

While most wind turbines are found on land, several countries have experimented with placing turbines offshore due to strong wind resources and limitations on suitable locations on land due to dense populations and existing developments.  Europe leads the world in development of offshore wind power, due to strong wind resources and shallow water in the North Sea and the Baltic Sea.  Denmark installed the first offshore wind farms, and for years was the world leader in offshore wind power until the United Kingdom gained the lead in October 2008.  The U.S. and other countries are now deploying offshore wind turbines to meet the energy demands of coastal communities.

Wind Energy Potential

Although wind power provides only about 1% of electricity used worldwide, it is growing rapidly, increasing more than fivefold globally between 2000 and 2007.  Generation costs have fallen by 50 % over the last 15 years, moving wind energy closer to the cost of conventional energy sources. Modern wind turbines have improved dramatically in their power rating, efficiency and reliability.

Like solar power, the potential wind power available in the atmosphere is much greater than current world energy consumption. The most comprehensive study to date found the potential of wind power on land and near-shore to be 72 TW, more than five times the world's current energy use in all forms.

Development, Deployment and Economics

Over the past ten years, global wind power capacity has continued to grow at an average cumulative rate of over 32 %.  In terms of economic value, the global wind market is estimated to be worth about US$36 billion annually in new generating equipment.

The top five countries in terms of installed wind power capacity are Germany (22.3 GW), the U.S. (16.8 GW), Spain (15.1 GW), India (8 GW) and China (6.1 GW).   The U.S. continues to lead as the biggest annual market, with 5.2 GW of new installations in 2007, followed by Spain and China, which added 3.5 GW and 3.4 GW to their total capacity, respectively.

By the end of 2007, the capacity of wind turbines installed globally had reached a level of more than 94,112 MW.  Over 70 countries contribute now to the global total, and the number of people employed by the industry worldwide is estimated to be up to 200,000.  In several countries, wind energy has achieved relatively high levels of penetration, accounting for approximately 19% of electricity production in Denmark, 9% in Spain and Portugal, and 6% in Germany and the Republic of Ireland as of 2007.

Although Europe still accounts for 65 % of global wind power capacity and most of the major wind turbine manufacturers, other regions are beginning to emerge as substantial markets for the wind industry, including the United States, Canada, China and India.

The future prospects of the global wind industry are very promising.  Even in a conventional scenario, the total wind power installed worldwide could quadruple from 40 GW in 2003 to 160 GW by 2012.

ADDITIONAL RESOURCES

American Wind Energy Association
http://www.awea.org/

European Wind Energy Association
http://www.ewea.org/

Global Wind Energy Council
http://www.gwec.net/