windmills

[boobesque]

i have seen 2 types of windmill. the fan blade type with a fin to turn into the direction of the wind, and a vertical type with 2 plane wing designed sides which catch the wind on one side while the other allows the wind to pass over it (due to the design of each wing). can anyone tell me which is a more efficient design for a small home made windmill (maybe 15-20ft high by 10-15ft wide)

[BillyBB]

The vertical wing style sometimes need to be powered up to start them. Some designs were self governing in high winds and very efficient. To see which design is the most practical, just look at a wind farm.

[Hippy]

The vertical sort are called Savonius rotors, try a google search on this for more info.

I think for a backyard installation they are more convenient and less likely to provoke the neighbours into hatred. They are just as efficient as the fan sort, and have the advantage that they are always correctly aligned with the wind.

[BillyBB]

Savonius Rotors are the half oil drum jobs. Two aerofoils mounted vertically are known as H-Rotor or Musgrove Rotor. Commonly three are used to prevent stalling at start up. Another similar design to look for is Darrieus Rotors.