Wind and air movement is generated as a result of unequal heating of the landmass and water bodies by solar radiation. The kinetic energy associated with the movement of large masses of air is the wind energy. This kinetic energy was harnessed by wind mills in the past to do mechanical work.
Kinetic energy can be used to do work. This work is used to power windmills, sail boats and gliders.

Principle of working windmill: The blades of a windmill are designed in such a way that when wind blows over them, a pressure difference is created over different regions. This pressure difference rotates the blades. To produce electricity, the rotatory motion of blades is utilized to rotate the turbine of the electric generator.
In a water lifting machine, the rotatory motion of the blades is made to do mechanical work.

Advantages of using wind energy:
(i) It does not cause pollution in the environment.
(ii) The cost of using fuel (i.e., air) is nil.