system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do wind electricity generators have three propeller blades?

If they had - say - six blades, wouldn't that mean that there would be twice as much torque and thus generating twice the power, while saving on other expenses (two times less stands, two times less land occupied etc)?
gpt
Six blades would mean more disturbance of the air so you'd lose efficiency. Ideally, the fewer blades the better really, but as with everything there are always compromises. One blade would put out-of-balance loading on the turbine gear so it would wear quickly, so you'd need two to make things balanced. But fewer blades means less power being extracted, so how to extract more power with fewer blades? Make them longer of course. But then that means the tower has to be taller so the blades clear the ground, and to ensure that the whole swept area of the blades is out in the higher winds higher up. 

But that introduces a third problem. Long blades mean that at the tips the blades will be going very fast indeed. Large wind turbines nowadays will have tip speeds approaching 200mph, so if you make them longer still that speed will increase, and as the speed increases the drag increases too so there's another loss of energy. 

TL;DR: Three blades are a good agreed compromise between efficiency and power output, taking all the factors into consideration.