The blades of a wind turbine. Photo courtesy of Michael Ashcroft
The method itself is very simple. The wind pushes on the blades which makes them spin. This spinning motion then (via some mechanical processes) turns a generator.
Generators work exactly like motors but in reverse. With a motor, you put electricity in and get motion out. With generators (dynamos) you put motion in and get electricity out.
If the blades spin faster, more electricity is produced. So, the amount of electricity generated is dependent on the speed of rotation of the blades.
Why have I emphasised that apparently obvious statement? Well, that feature determines many of the physical properties of wind turbines that we know and love/hate (delete as appropriate).
Wind turbine features
Photo courtesy of Mr. T in DC
Height
You may have wondered why the turbines are on tall towers. It is because, on the whole, wind speed increases with altitude, so the higher you go, the high the power output.
Bigger really is better in this case. The height of the pole also keeps the blades out of the way.
It is more than that though: there is an equation which shows the relationship between the power output of a turbine and the speed of the wind making it turn.
You can sum it up by saying that the amount of power is proportional to the wind speed cubed.
Not only does power increase with height, but it increases significantly. You get 125 times more power when the wind speed is 10 metres per second (22.4 mph) than when it is 2 metres per second (4.5 mph)!
Height significantly affects how wind turbines work in terms of their power output.
Blade diameter
Increasing the blade diameter increases the amount of torque the wind is able to exert on the blades. More torque means that you get more energy from the wind.
It is like using a long crowbar to open a door as opposed to using a short screwdriver.
Types of wind turbine
A vertical axis wind turbine. Photo courtesy of thingermejig
Though everyone is used to the image of the modern, wind farm turbine, towering high above the land and visible from miles away, there are other kinds.
They exist in much smaller sizes, which are particularly suitable as residential wind power.
The common power outputs of the large turbines are of the order of 1MW, 2MW and so forth (enough to power, assuming each household uses a pessimistic 2kw, 500-1000 homes).
Smaller, residential wind turbines are normally around the 1kW mark (and are correspondingly much, much smaller).
There are also some new and novel designs, which are wildly different from the norm.
Vertical axis turbines, for example the one in the photo to the right, are stunningly beautiful (says I), and take up much less space.
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