Wind power has been used by humans in one form or another for over 2000 years. In its infancy, the Persians and the Romans used windmills to grind grain. Windmills were used in 14th-century Holland to pump water. Today, wind turbines are used to generate electricity. Even after 2 millennia, the basic concepts to harness the wind have not changed, but have only been refined.
Types of Windmills
There are 2 main categories of windmills: horizontal axis and vertical axis. Horizontal axis windmills consist of straight vertical blades connected to a central horizontal shaft. Vertical axis windmills consist of vertical blades that are attached at both ends to a vertical shaft.
Horizontal Axis Windmills
The earliest windmills were built in Persia around 250 BC in the horizontal configuration. The horizontal windmill design, consisting of four or more large rectangular blades covered in fabric, reached its peak in 19th century, with over 2500 windmills in Denmark alone. These windmills had a gear system that transfered the rotation from the horizontal shaft to a vertical shaft centered in the windmill housing. The vertical shaft was connected to a millstone system for grinding grain, or additional gear and shaft systems to transfer the power to where it was needed.
With the development of aeronautical principles and advanced materials, the design of the blades changed radically to the airfoil designs used today. The turbine blades of today's windmills can be adjusted via motors to optimum angles based on wind speed, and are created from materials that can withstand the high stresses that are encountered.
Vertical Axis Windmills
The first people to successfully use vertical axis windmills were in what is now Afghanistan in the 7th century AD. These windmills contained a number of rectangular blades covered in cloth. At the time, these windmills were used for grinding corn and pumping water. Advances in aerodynamics and the development of the airfoil also provided improvements to the vertical axis design. Modern vertical axis windmills have been nicknamed "eggbeaters" due to their resemblance to the kitchen tool. Vertical axis windmills can be located closer to the ground than their horizontal counterparts, but have a reduced efficiency caused by drag on the blades.
Wind Turbines to Generate Power
The first wind turbine built to generate electricity was erected in Scotland in 1887. In the early 20th century, windmills were used extensively in rural areas to provide electricity to farms. The first mega-watt wind turbine was built in Vermont in 1941 under a Department of Energy program. Over time, wind turbine designs were refined and in fact customized to specific locations, such as offshore, mountain, forest, or plains, in order to extract the most power from the available wind. The largest wind turbine currently in production is the Enercon 126. This 6MW machine has an overall height of 198 m (650 ft) and a diameter of 126 m (413 ft). The largest producer of wind power in the world is currently Germany, who produced over 22,000MW of power in 2007.
Wind power is a sustainable energy source that can be collected by small residential turbines, or in large industrial wind farms. Wind power is quiet and clean, and is a favorable alternative to power generated by fossil fuels. Despite their modern advances, wind turbines would still be recognizable to the first who harnessed the wind over two thousand years ago.
Sources
History of Wind Power, Wind Turbine
Susan Kristoff - Susan Kristoff is mechanical engineer by trade, but has a diverse set of professional and personal interests. The glue that binds all of ...
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