How Much Power Can We Extract?
We cannot extract all the power in the wind. If we extract all the energy from the wind then the air would stop moving behind the wind turbine, and thus air coming in downstream would be blocked. Since wind is the result of movement of air. If the air stops moving, there will be no wind.
In 1919, a German physicist Albert Betz, based on conservation of momentum and energy, he proved that the maximum possible energy that can be derived from a wind turbine cannot be more than 59.3 percent, or 16/27 of the potential energy in the wind.
In practice, no wind turbine has ever achieved the Betz limit.
How does a wind turbine works?
A wind turbine is a device that converts the potential energy in the wind to electrical energy. It gets its power from slowing down the wind by the blades. The blades cause the shaft of the alternator to rotate. The alternator generates electricity when the magnet wires cut through magnetic flux induced from the Permanent Magnet. The magnitude of the voltage output from the alternator is proportional to the speed of rotation of the shaft.
The output of the wind turbines can be stored in battery banks or connected to electricity grid. Since the output of the alternator varies all the time because the natural wind is never constant. Therefore, regulating devices must be installed in order to use the generated electrical power properly.