Efficiency
Efficiency of a machine is determined by the work put out by the machine, over the work put in the machine. In a wind turbines case, the work put into the machine is the wind and the work put out is the electricity it made, or the amount of wind it captured. The Betz law states that it is not possible for a wind turbine to capture 100% of the energy, if it did, the wind would have no kinetic energy and would stop. On the other hand, if you had 0% efficiency, the wind would just be flowing right past, so you have to find a perfect balance that allows you to capture some of the energy and still allow the wind to flow through. This perfect balance is around 59% efficient but because of varying wind speeds and conditions, it’s hard to tell. In the end, it doesn’t really matter how efficient the wind turbines are because we are not going to run out of wind.