By Benjamin Kahane.
For hundreds of years, humans have used wind to pump water and grind grain, mostly with small windmills. Large, modern wind turbines are used to generate electricity for individual use and to feed into the electric grid. Wind turbines generally have three blades and, because higher altitudes yield higher wind velocities and lower turbulences, the turbines are mounted on tall towers to capture as much energy as possible. As the blades turn, the central shaft spins a generator to make electricity.