The Way the Wind Blows
Q. The wind turbines that generate electricity seem to have just three blades, or sometimes two. Why so few?
A. As many as 90 percent of the turbines in use now have three blades. But experiments are still underway to determine what number of blades works best in terms of efficiency, durability and economy.
When the wind shifts, the three-blade design minimizes vibration or “chatter.” A two-blade system is subject to considerable chatter when the blades are in the horizontal position, with associated wear and tear on the turbine. The chatter is sometimes audible.
A design with only one blade would actually be the most aerodynamically efficient, but the single blade would move very fast, producing objectionable noise, and it wears out the assembly more quickly.
Adding a fourth blade increases energy production by only a small percentage, and the added expense is comparatively large.
Finally, many people consider the three-blade turbine to be the most aesthetically pleasing design.