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Wind Farming

Author: Dr Hermann Oelsner ~ MD, Oelsner Group

( Article Type: Explanation )

Energy from the sun sent to earth every year is equal to more than 15 000 times the commercial energy consumption of the world’s population. Almost half of this energy is naturally converted into wind. The theory and practice of using wind energy to do work for mankind is well known and tested. It has been used for centuries, for the purpose of milling, water pumping and many other applications. However, it is only in the last half of the 20th century that people started to explore the use of wind energy to generate electricity. Historically the international interest in electricity generation from wind power was sparked by the world oil crises in 1973 and 1979 when, in addition to the problem of the security of fossil fuel supplies, the focus of developed countries became more environmental. Because of the political focus on environmental issues and, of late, the hot topic of global warming and greenhouse gases, the wind energy market has experienced an enormous growth period over the past 20 years. Commercial wind farms are now being operated on a more competitive basis then ever before. A wind farm typically consists of a group of large wind turbines, which supply the generated electricity directly into the national grid. The movement of air propels three blades mounted on a hub and horizontal axle, transferring the energy to a gearbox and generator where the electricity is generated. The gearbox and generator are housed in the ‘nacelle’, which is mounted on top of a tubular steel tower. Wind turbines come in all shapes and sizes and range from 200 Watts to 3.5 Mega Watts.

South Africa has an abundance of wind resources, especially in the coastal regions. There is, however, not yet one large wind turbine installed. The government has declared the 13MW Darling Wind Farm, north of Cape Town, as a National Demonstration Project which went on line in September 2002. On this wind farm, there will be 10 wind turbines with a generating capacity of 1 300kW. Each wind turbine has a hub height of 50 metres (the same height as a 17 story building). The length of one blade is 32 metres (longer than a tennis court). Less than one percent of the land on which the farm is situated is used for the foundations and roads, with farming operations continuing as usual.

The National Demonstration Wind Farm is envisaged to:

  • Demonstrate to the public and other interested parties not currently informed or educated about wind energy;
  • Present an opportunity for technology transfer, training and practical experience for the industry and potential wind energy supporting industries and organisations.

During its 25 years of operational life, the anticipated benefits will be:

  • Savings of national resources
    • Coal: 450 000 tons
    • Water: 1 130 000 litres
  • Avoided release into the atmosphere
    • Carbon dioxide: 850 000 tons
    • Sulphur Dioxide: 10 400 tons
    • Others: 55 500 tons