The purpose of a wind turbine is to take kinetic energy (wind energy) and change it into electrical energy. To determine kinetic energy from the wind, we start with the basic formula:
KE = 1/2 * mass * velocity^2
In our equation, velocity is equal to wind speed. But what about mass? At first, I was puzzled, but mass in this case has to be related to the volume and density of the air hitting the rotors of the wind turbine, so:
KE(wind) = 1/2 * air volume * air density * velocity^2
The above equation would allow you to find the kinetic energy of the wind, which (theoretically, some is lost) is transferred into electrical energy. Generally when measuring wind energy, a more useful equation tells us the power of the wind. Power is essentially energy divided by time. Obviously, determining the wind energy over time helps us see where best to place wind turbines and whether they are being effective. The equation for wind power is:
P(wind) = (KE wind)/(change in time)
Wind turbines change wind energy into electrical energy, but really this is only one form of kinetic energy into another. There is much ongoing research about using wind turbines to change the kinetic energy of the wind into a stored potential energy. Particularly, there is interest in integrating energy storage with energy generation.
After wind turbines convert wind energy into electrical energy, this electrical energy needs to further be converted into an energy that can be stored. When it is time to harness this energy, it is then converted back into electrical energy. Each of these conversions causes a loss of energy and is also fairly expensive. Integrating energy storage inside a wind turbine could give access to a more constant flow of electrical energy when it is needed and eliminate some energy conversions.
For example, wind turbines (as windmills used to do) could pump water up a hill and then whenever people choose to release the water they could harness that energy and convert it to electrical energy. The author of my article suggests using gas compression as a means to store potential energy converted from wind energy inside the wind turbine.
I think it's neat that energy is all around us and that by being a little more inventive we can find all sorts of harmless ways to create usable energy.