Wind Power

In reality, wind energy is 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 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"). Some portion of that energy can converted into other forms mechanical force or electricity that we can use to perform work.  

A wind energy system transforms the kinetic energy of the wind into mechanical or electrical energy that can be harnessed for practical use. Mechanical energy is most commonly used for pumping water in rural or remote locations- the "farm windmill" still seen in many rural areas of the U.S. is a mechanical wind pumper - but it can also be used for many other purposes (grinding grain, sawing, pushing a sailboat, etc.). Wind electric turbines generate electricity for homes and businesses and for sale to utilities.

There are two basic designs of wind electric turbines: vertical-axis, or "egg-beater" style, and horizontal-axis (propeller-style) machines. Horizontal-axis wind turbines are most common today, constituting nearly all of the "utility-scale" (100 kilowatts, kW, capacity and larger) turbines in the global market.

Electricity generated by a utility-scale wind turbine is normally collected and fed into utility power lines, where it is mixed with electricity from other power plants and delivered to utility customers. Today turbines with capacities as large as 5,000 kW (5 MW) are being tested.

• New wind projects added in 2007 account for about 30% of the entire new power-producing capacity added nationally in the year.
• By reducing the use of natural gas and other fuels used for electricity generation, and lowering the pressure on their price, wind can save consumers money, even in regions with low or no wind
  resources.
• To generate the same amount of electricity using the average U.S. power plant fuel mix would cause over 28 million tons of carbon dioxide (CO2) to be emitted annually.
• Shattering all its previous records, the U.S. wind energy industry installed 5,244 megawatts (MW) in 2007, expanding the nation’s total wind power generating capacity by 45% in a single calendar year and injecting an investment of over $9 billion intothe economy.
• The U.S. wind power fleet now numbers 16,818 MW and spans 34 states.
• American wind farms will generate an estimated 48 billion kilowatt-hours (kWh) of wind energy in 2008, just over 1% of U.S. electricity supply, powering the equivalent of over 4.5 million homes.
• Texas consolidated its lead in terms of installed wind power capacity. The states with the most cumulative wind power capacity installed are: Texas, with 4,356 MW; California, with 2,439 MW; Minnesota, with 1,299 MW; Iowa, with 1,273 MW; and Washington with 1,163 MW.
• At least fourteen new manufacturing facilities opened or were announced in2007. 
• GE Energy continued to lead in wind turbine sales, with 45% of the market in terms of new capacity installed.
• FPL Energy remained atop the list of wind project developers, with 956 MW of new development in 2007 alone.

Source: The American Wind Energy Association, 2008