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Wind Power

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Humans have been harnessing the wind's energy for hundreds of years with windmills which have been used for pumping water or grinding grain. A wind turbine - the modern equivalent of the windmill - uses the wind's energy to generate electricity.

Wind turbines are mounted on a tower at about 30 metres above ground where they can take advantage of the faster and less turbulent wind to capture the most energy.  They usually have two or three propeller-like blades, mounted on a shaft to form a rotor, which catch the wind’s energy.

When the wind blows, a pocket of low-pressure air forms on the downwind side of the blade. The low-pressure air pocket then pulls the blade toward it, causing the rotor to turn. This is known as lift. The force of the lift is much stronger than the wind's force against the front side of the blade, which is called drag. The combination of lift and drag causes the rotor to spin like a propeller, and the turning shaft spins a generator to make electricity.

Wind turbines can be used as stand-alone applications, or they can be connected to a utility power grid or even combined with a photovoltaic (solar cell) system. To provide a greater source of wind energy, large numbers of wind turbines are usually built close together to form a wind farm.

South Africa has an abundance of wind resources, and there are two key wind power projects in South Africa: at Klipheuwel and Darling, both in the Western Cape. The Western Cape's winds are considered perfect for wind energy - prevailing winds are from two directions, and usually blow during peak electricity consumption periods.






Last modified 2006-04-20 11:42 AM