Best Alternative Energy Source: Wind Turbines

I believe wind turbines are the best energy source. Wind is free so we can use as much as we need. The energy that is produced does not emit harmful gases and is renewable. All though wind turbines are very good for the environment, there are also downfalls. When the turbines are being built, the factory releases gases. Also, the wind speeds aren't always constant. A solution to that would be to move to a place where there is a lot of wind.
Even though wind turbines have a few downfalls, I still believe they are good because they don't emit harmful gases.