How is the energy wind power generated?

Wind blows on usually a 3 blade design that is angled with a small angle perpendicular to the wind direction.

The blades change the direction of the wind and in doing so they extract energy from the wind energy. If the wind comes in at 15 m/s it might leave the blades at 10 m/s. That 5 m/s of wind energy is converted into rotational motion of the blades which are connected to a generator shaft.

The area of the circle that the blades travels in is the theoretical power the blades can extract from the wind. For instance, if the blades are 30 meters in diameter the area swept by the blades is area = pi * r^2, so area = 3.14 * 15 squared = 707 square meters of area

So if you take all the wind power of moving air traveling thru an area ,that is 707 square meters in this case, and the blades job is to grab as much of this energy in the 707 sq m as possible and convert it to rotational motion which can then turn a generator. A spinning generator makes AC electric current

In theory , a windmill can only convert a little less than 60% of the wind energy into electricity, because once the wind goes thru the blades it has to have enough energy to get out of the way to let new wind energy come into the blades