By: Dr Hermann Oelsner (for Enviropedia)
Energy from the sun sent to earth every year is equal to more than 15000 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 know 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 have 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 crisis 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 a tremendous growth period over the last 20 years. Commercial wind farms are now being operated on a more competitive basis than ever before. A wind farm typically consists of a group of large wind turbines, which supply the generated electricity directly into the national grid. Th movement of the air propels three blades mounted on a hub and horizontal axle, transferring the energy to a gearbox and a generator where 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 Megawatts.
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 1% of the land on which the farm is situated is used for the foundations and roads, with farming operations continuing as usual.
During its 25 years of operational life, the anticipated benefits will be:
Coal: 450 000 tons
Water: 1130000 litres
Carbon Dioxide: 850 000 tons
Sulphur Dioxide: 10 400 tons
Others: 55 500 tons