Wind Energy

History:
Wind energy is not a new technology.  As early as 200 BC simple windmills were used to pump water in China and vertical axis windmills were used in Persia and the Middle East to grind grain.  The Dutch reinvented the windmill after the 11 th century to drain water from marshes and lakes.  The 19 th century brought the technology to America where it was used largely for pumping water and creating electricity on farms and ranches.  Though the industrial revolution led to a reduction in the use of this technology, the first large scale wind turbines were produced in the late 1800’s in Europe and the 1940’s in the US. 

Increasing oil prices in the 1970’s revived an interest in wind energy.  Old technologies were updated to turn wind power into useable electricity feeding the utility grid of the United States and Europe.1

Wind:
Ultimately, all renewable energy, except geothermal and tidal power, comes from the sun, a total of 174,423,000,000,000 kilowatt hours of energy per hour.2 About 1 to 2 percent of this energy is converted into wind energy.  Temperature differences between the equator and the poles create air circulation: warm air at the equator rises and moves towards the poles where the air cools and sinks.  Because the earth rotates, the wind tends to rotate counterclockwise around low pressure areas in the Northern Hemisphere and clockwise around low pressure areas in the Southern Hemisphere.  This phenomenon is known as the Coriolis force. These wind patterns are called geostrophic winds, or global winds, which are affected by temperature and pressure differences and are found 1000 meters above the earth’s surface.  Local winds are affected by the earth’s surface, mountains, and bodies of water, and may differ slightly from global winds.  Overall wind direction, then, is determined by a combination of global and local wind patterns.3

Energy:
Wind power is converted into energy when the force of the wind becomes torque, or turning force, acting on the rotor blades.  The amount of energy generated depends on the density of the air, the rotor area, and the wind speed.

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1. US Department of Energy, “History of Wind Energy,” http://www1.eere.energy.gov/windandhydro/wind_history.html.
2. Danish Wind Energy Association, “Where Does Wind Energy Come From?” http://www.windpower.org/en/tour/wres/index.htm.
3. Ibid.
Photo by Whitney Parks

 

 

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