History

• Wind power has been around for thousands of years. Up until the 19th century, sailing ships were responsible for almost all water-borne transportation and shipping, as well as military ships. Wind has also been used on land to do work for a long time. Between the 6th and 10th century, people in Persia began to use windmills to grind grain and to pump water from wells. Windmills have also been used in China for a long time, perhaps 2000 years or more, although no one knows for sure when the Chinese developed the technology. Beginning in 1390, the Dutch began to take the windmill to a whole new level, improving the design of the blades and attaching them to multi-level towers that were specially designed to process grain and provide homes for families of the millers. Beginning in the 19th century, small multi-blade windmills were pioneered in America for irrigation and other purposes.
  
  

Significance

• Wind power has been one of the most important driving forces in the evolution of human civilization. For thousands of years it powered ships, allowing sailors to explore, trade, and conquer. As technology advanced, wind was harnessed to power irrigation systems, grain mills, and even some industrial machines. Until recently, wind has been supplanted by fossil fuels and nuclear power, but as environmental pressures increase, wind can provide a crucial source of clean, cheap energy.
  
  

Types

• There are three main types of wind power: sail power, mechanical power, and electric power. All three use an airfoil to generate power. A sail can be thought of as a simple airfoil. When the wind blows against the inside curve of the sail, it creates a low pressure area on the outside of the airfoil, pulling the boat forward. A windmill combines several airfoils in a fan shape, using the lift from the wind to drive them around in a circle, rotating a shaft. Mechanical windmills use the power of this rotation to perform some mechanical task. For example, a grain mill turns a huge stone to grind grain into flour. Electrical windmills turn a generator. The rotation is used to move a coil in and out of a magnetic field, generating current.
  
  

Size

• Global wind power output has grown by 10 percent or more in every year since 1980 but two, and the growth shows no sign of slowing. In 2007, enough wind power was produced to provide power to about 70 million homes. In Denmark, more than 19% of total electric power comes from wind generators. Nonetheless, wind is still just a drop in the bucket for most of the world. In the United States, for example, it provides less than 1% of the total electric power.
  
  

Considerations

• Wind is a clean technology. It takes some energy to build, transport, set up and maintain wind turbines,but very little compared to the amount that is produced. Wind farms do require quite a bit of space, which is a problem in densely populated areas. Some countries such as Denmark and the UK have built offshore wind farms to take advantage of the powerful winds over the ocean.
  One problem with wind power is the unpredictable nature of the wind. A quiet spell can quickly cut energy production to almost nothing. For this reason, wind needs to be supplemented by other resources. The wind farm can be used to complement a conventional generators. Technicians can increase or reduce energy production in the traditional plant according to the energy wind energy available at a given point.