Balancing Wind Turbine Blades

Learn how to balance the blades on your DIY wind turbine

It is essential that the blades on a wind turbine generator are correctly balanced whether you have a cheap pair of home made PVC wind turbine blades (1) or you've gone to the trouble of carving your own wooden wind turbine blades (2).

In practice it is unlikely that the alternator / generator (3) will be perfectly balanced, so the process of balancing the blades will actually balance the whole unit. It wind turbine blades are not correctly balanced then terrific vibrations will quickly destroy your wind turbine generator.

How to Balance Wind Turbine Blades

Wind turbine blade balancing is actually a very simple process, but you must do it on a totally still day (i.e. no wind) or do it indoors. Pieces of lead flashing (used by roofers) work best as they are soft (easy to screw in place) and very dense. It can be obtained in flat sheets from a builder's merchant or you can use fishing weights can be hammered flat. Fix the blades onto the alternator in what you intend to be their final positions numbering each blade and the alternator accordingly so that you can take everything apart and put it back together again correctly in future.

Now gently spin the turbine and leave it too come to a complete stop. Whichever side is the heavier will finish at the bottom (6 o'clock position). Raise the heavy side up to the 3 o'clock position and add a weight on or near the hub at the 9 o'clock position (and more weights if necessary) until it balances - i.e. the weight(s) remain at the 9 o'clock position with the previous heavy side at the 3 o'clock. Gently spin the turbine a few more times. If it stops at the same point each time, then that is the new 'heavy side' and you need to repeat the steps listed above. Very quickly you will have a balanced wind turbine and you will not need to re-balance it again unless you replace a damaged turbine blade in the future.

Balancing wind turbine blades with lead flashing

An alternative way to balance wind turbine blades (pictured above) is with a weight and a tape measure. Spin the turbine around to get one of the blades in the horizontal position. Stop the turbine. Sit a weight on the blade as close to the hub as possible. Slowly move the weight outwards until it causes the turbine to rotate - measure this point. Repeat this with each of the blades of the wind turbine generator. If the three measurements are the same then the blades are all balanced. If however the measurement for one of the blades was greater, that blade is lighter and so a lead weight should be screwed to the alternator where the light blade connects to it.

A further way to balance wind turbine blades is to hang the blades and hub from its centre using very strong string. Add weights where necessary near to the hub until the blades all sit level.

Web Link References

(1) http://www.reuk.co.uk/PVC-Wind-Turbine-Blades.htm
(2) http://www.reuk.co.uk/Make-Your-Own-Wooden-Wind-Turbine-Blades.htm
(3) http://www.reuk.co.uk/Permanent-Magnet-Generator.htm

Article from REUK.co.uk:
http://www.reuk.co.uk/Balancing-Wind-Turbine-Blades.htm
Published: 31st January 2007
© REUK 2009