Environmental Engineering Reference
In-Depth Information
North Pole
Polar cell
Polar easterlies
60º
Ferrel cell
30º
Westerlies
Hadley cell
Trade winds
Equator
South Pole
Figure 1: Idealized atmospheric circulations.
North Pole and fl ows along the earth's surface toward the equator. Near north lati-
tude 60°, the Coriolis effect becomes signifi cant to force the airfl ow to southwest.
2.3 Local geography
The roughness on the earth's surface is a result of both natural geography and
manmade structures. Frictional drag and obstructions near the earth's surface gen-
erally retard with wind speed and induce a phenomenon known as wind shear. The
rate at which wind speed increases with height varies on the basis of local condi-
tions of the topography, terrain, and climate, with the greatest rates of increases
observed over the roughest terrain. A reliable approximation is that wind speed
increases about 10% with each doubling of height [4].
In addition, some special geographic structures can strongly enhance the wind
intensity. For instance, wind that blows through mountain passes can form moun-
tain jets with high speeds.
3 History of wind energy applications
The use of wind energy can be traced back thousands of years to many ancient
civilizations. The ancient human histories have revealed that wind energy was
discovered and used independently at several sites of the earth.
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