the number of blades makes it less efficient as it has more drag, each blade also creates turbulence behind it that affects the next blade, if you are going to have a whole bunch of blades like a turbine does then you need a set speed, for that you need to control the speed of the wind... good luck with that!
Yes, one blade is most efficient, but it is not stable, two blades is balance but it creates this weird gyroscope half the time when the blades are parallel, then when they are vertical that gyroscopic action disapeers almost 100% allowing it to twist, jump, shake and do whatever it wants in that moment... three blades make a stable wheel but they are also spaced out enough that they can act as air foils, like a wing, three of them are easy to adjust the pitch of, like you would with a wing for varied wind speed, all around three blades seem like a good idea, unless you want a drag device, like an old water pumping wind mill those blades act as drag devices, they are pushed by the moving air, they can never go faster then the air speed, a three blade prop can have the tips of the blades brake the speed of sound! it is an issue that has been delt with.
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