Space/Science — HabitableZone

Space/Science » in reply to Why don't they put more blades and then add a variable transmission so that the blades spin slower, while producing more electricity?

More blades doesn't necessarily mean more energy...
Larry J — (archived)

gets extracted from the wind. What counts is the disk area (the area swept by the blades as they rotate). Think of the energy in a small stream verses a river - even at the same water velocity, the river represents much more energy.

Consider the old multiblade windmills dating back to the 1800s. They were designed to be easy to build and to generate torque to drive a pump. It turns out they aren't efficient at generating electricity. A 2 or 3 blade design that sweeps out a large area is much more efficient. Some of them do use variable blade pitch (like an airplane propellor) to more efficiently extract energy from the wind.

While the problem is reversed, a windmill is similar to an airplane propellor. Interestingly enough, adding more propellor blades doesn't increase propellor efficiency. In fact, the most efficient propellors ever made actually have only one blade. They're hard to balance, but it has been done as seen here (check the "Silent Club fuel-injected self-launch video). Multiblade propellors can allow you to harness more engine torque for a given diameter (related to prop clearance and noise production), but they really aren't more efficient.

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