To produce the most electricity, wind turbines need to be located in areas where the wind blows at a constant speed, which it does not do in all parts of the world. For example, Class 7 winds are extremely strong, while Class 2 winds are mild breezes. Generally, Class 4 winds and above are considered adequate for a wind turbine to produce electricity. Large groups of wind turbines, called wind farms or wind plants, are connected to electric utility power lines and provide electricity to many people. New turbine designs now take advantage of less windy areas by using better blades, more electronic controls, and other improvements.
Some new turbines can also operate efficiently over a wide range of wind speeds.
In theory, wind systems can produce electricity 24 hours every day, unlike PV systems that can't make power at night. However, even in the windiest places, the wind does not blow all the time. So, while wind farms don't need batteries for backup storage of electricity, small wind systems do need backup batteries. And, we're still learning about local wind patterns and how they affect wind turbines and blades. We can also get energy directly from the heat in the earth.