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For
centuries, the winds moved ships and people and cargo from place to place. Christopher
Columbus could never have discovered the New World. Without wind, exploration of the high
seas would have had to wait for the invention of the steam engine in the eighteenth
century.
But the wind served more than sailors and explorers. It has been used to grind grain since
the 7th century. In fact, we still call almost any machine that is powered by the wind -
no matter what job it does - a wind "mill".
In 15th century Holland, windmills ran factories that sawed timber, processed wool and ground spices. Farmers in the United States and Australia have used wind to pump water to cattle and crops since the mid 1800’s. By the early 1900’s, there were more than 6 million water pumping windmills in the US, and there are still thousands operating today.
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In 18th century colonial Williamsburg, Virginia, the local mill was built as a post mill, Robertson's Windmill. The wind shaft and millstones were housed in a house-like structure atop a huge post. The stairs the mill lifted up so that when the wind changed direction, the mill could be rotated on the post to face into it. |
Today, wind power is starting to become popular again. In California, "wind farmers" have set up hundreds of wind turbines in breezy mountain passes and sell the electricity generated to major utility companies. There are now more than 15,000 wind turbines in California producing enough power to meet the needs of about one million people. California produces 80% of all of the world’s wind-generated electricity. Denmark produces much of the rest with Australia, Germany, Spain, the Netherlands, the British Isles and India also generating large amounts of electricity from the wind.
What makes the wind blow?
There are variations in temperature over the face of the Earth Where the sun heats the Earth, the land gets warmed and so does the air above it. As the air heats up, the molecules of air begin to move faster and faster and move farther and farther apart. This makes the air less dense and lighter in weight. Warm air rises.Meanwhile, air over the ocean and colder climates remains cooler. In cold air, the molecules move more slowly and remain closer together making the air more dense....heavier. Since it is heavier, it pushes down more. In other words, its pressure is higher.
Wherever there is enough difference in air temperature, there is a difference in pressure. If the difference is great enough, the air moves from the area of high pressure to the area of low pressure trying to keep things equal. The bigger the difference, the faster the wind blows.
Copyright ©1996-97 Wintec Energy, Ltd.
Last modified: December 28, 1998