How many blades?

For a horizontal windmill the number of blades may vary between one and forty. Mills for power generation normally have two or three; mills for pumping water require more.

The graph at right gives the ‘power coefficient’ ( a measure of the power generation) vs the number of blades.

What does the graph mean? If you were putting a up a windmill to generate a lot of power, would you use few blades or many? Are there other factors which might need to be considered?


Comments

The graph indicates that the amount of power generated increases with the number of blades, but only slightly. So the benefits of that increased power must be balanced against the increased costs of the extra blades and a stronger supporting framework.