Energy sources
WIND
What is it?
On a windy day, you might go outside and fly a kite. The kite flies high and swirls around in the air, dipping and rising, thanks to the force of the wind. It's all great fun but did you know that wind can also be used as a source of energy?
Wind is caused when the sun heats the air and the earth's surface unevenly causing a difference in the atmosphere. Wind has been used as an energy source for thousands of years. Up to 4000 years ago, the Babylonians and the Chinese used wind power to pump water for crops, and sailing boats were around long before that. Wind power was used in Europe in the middle ages to mill (meaning grind) grain. This is where the term windmill comes from.
How does it work?
Today, windmills, or wind turbo-generators, are used to generate electricity. The blades or sails or the turbine drive the generator. To increase the amount of electricity produced, a number of turbines can be placed together in the same area, forming a wind farm.
The best places for wind farms are coastal areas, gaps in mountains, the tops of rounded hills and open plains. To be economical, the average wind speed at a wind farm should be about 25km/h.
Wind turbines have four main features.
- Blades
- Shaft
- Generator
- Tower
The blades look like propellers on an aeroplane, except that instead of creating wind, they catch the wind. The shaft is connected to the blades, and it rotates as the blades turn with the wind. The shaft runs to the generator. The generator transforms the rotations of the shaft (mechanical energy) into electrical energy.
Advantages
Wind is free and renewable - there will always be wind and everybody has access to it. It produces no greenhouse gases and the land used for wind farms can usually be used for other things as well (like farming). Wind farms can be popular tourist attractions thanks to the sheer number of them in one area. They are also an excellent choice for remote areas that are not connected to the main electricity grid.
Disadvantages
The wind speed changes often, and some days have no wind. This can make it an unreliable source of energy. Very windy areas are hard to find, and are often near the coast where land is more valuable. Some people think they spoil the landscape - as they can be very large and can affect the view. The generation of wind power can also be noisy, and can kill birds (migrating birds and windmills both like strong wind).
Use in Australia and around the world
Wind power generates less than 1% of the electricity in Australia, but more wind farms are being built every year. Ergon Energy purchases electricity from a wind farm built by Stanwell Corporation at Windy Hill on the Atherton Tablelands. The wind farm consists of 20 wind turbines generating up to 12 MW of electrical output.
Ergon Energy also operates a number of other wind turbines; including two on Thursday Island off the Northern tip of Queensland. The largest wind farm in Australia opened in 1998 at Crookwell in New South Wales. The $10 million wind farm can supply electricity to 3500 homes.
In the USA and Europe, some wind farms have hundreds of turbines. There are enough wind turbines in the USA to power 300,000 homes.
