How Windmills Work

Background

Windmills have always been used to harness wind power, but over time the application of that power has shifted. The earliest known windmills, constructed in Persia during the 7th century AD had a vertical axis and were often used to transport water. Europeans first introduced the horizontal-axis windmill most recognize today. These were very popular for grinding corn and other grains for the production of flour. Today, windmills are almost exclusively used to generate electricity.

Traditional Windmills

Windmills use blades that resemble the wings of airplanes to gather wind that flows over them. Like a wind, the shape of the blade produces a difference in pressure on the opposite faces, which for an airplane produces lift and in a windmill turns a central drive shaft. In traditional windmills, the shaft is connected through a series of gears to a stone or some other grinder. Others were equipped to power saws or pump water. For the production of electricity, the drive shaft is linked to a generator, which, as the blades turn, creates electricity.

Electricity from Wind

Modern windmills are called wind turbines and are positioned in large groups called wind farms to take advantage of natural wind corridors, some of which are actually off shore. Turbines produce about forty percent of all electricity on earth, but are usually driven by steam heated by the burning of fossil fuels or the application of nuclear fission. Wind powered turbines are an attractive alternative because they produce zero emissions and use a fuel source that is entirely renewable. But no matter how they're powered, turbines are connected to generators which induce the movement of electrical potentials existing within transmission wires. Turbine-driven generators, which use motion to produce electricity, are essentially the opposite of motors, which use electrical energy to produce motion.

Individual wind turbines can generate about 100 kilowatts of energy -- turbine farms can create several megawatts. The world's largest wind farm, in Texas, has 421 can power 220,000 homes per year. The major drawbacks to wind energy have been the cost of producing and maintain wind farms, and the limitations created by a reliance on wind. Over time, however, technology has improved the efficiency of wind turbines, making it a cost effective enterprise for producers and consumers alike. Though it's unlikely wind power could ever meet all of humanity's electricity need, it has become a viable part of a diversified energy generation profile.

Resources

• Windmill
• Wind Turbines
• Wind Energy Basics