Siting small scale wind turbines

As you may have read here before, wind energy can be captured very efficiently by large, offshore wind turbines. In fact, the larger the better.

Despite this, there is still a place for smaller wind turbines – just so long as it’s the right place. So what is the right place to site a small scale wind turbine? Here a few simple guidelines:

1. Somewhere windy

Stating the obvious here. To be more precise, if you want a small wind turbine but your site doesn’t receive an average annual wind speed of 5 or 6 m/s then it would be wise to think again. You may think you live somewhere windy, but it is advisable to find out what your average wind speed is using an anemometer. Better Generation make the Power Predictor which you can put up on a pole to measure your wind speed. Far better shell out a few pounds now that to find that the wind turbine you bought is just an expensive weather vane. What’s more, you can pass it along to someone else once you know what winds you can expect.

2. The higher you can site the turbine, the better

Wind speed is higher, the higher you go. This means that if you have a taller mast to site your turbine, you will get a better energy return. Much better. As the speed of the wind doubles, the amount of ‘potential’ power contained in the wind does not double – it cubes. If the wind speed doubles, the power increases eight-fold (this also means if the wind speed halves, the power decreases by a factor of eight – bad news for slow wind speeds!).

If you can site your turbine high up at the top of a hill you can also exploit the aerodynamic effect which makes wind speed up as it passes over an obstruction. This is the same effect that gives an aeroplane wing its “lift”.

3. Stay well clear of buildings and trees

Wind turbines hate turbulent wind conditions. Even if you have decent average wind speed, if that wind is gusty and turbulent your turbine will not be able to consistently generate power. Manufacturers of vertical axis turbines (the ones that look like whisks) will say that their turbines perform better in turbulent conditions than a horizontal axis turbine will. This may be true (many are sceptical) but it is unlikely to make an non-viable site viable.

Guidance is that the distance to the obstruction should be at least 10 times the height of the obstruction. A higher mast can also help and a rule of thumb is that the turbine hub should be twice as high as any nearby obstruction.

4. Push the boundaries of small!

Bigger is better with wind turbines. This is a simple way of stating that the power of a turbine increase with the square of the rotor diameter. The longer the turbine blades, the greater the diameter of the rotor and therefore the more wind can be “captured”.

These four simple guidelines should help you to decide if a small wind turbine is right for you, and if it is, where the best place is to site it. If you’re hungry for further information, keep your eyes peeled for Small Scale Wind Power Generation by myself and Gavin Harper, forthcoming from Crowood Press and soon to be found in all good bookshops.

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