All energy, even wind, originates ultimately from the sun. The earth receives 1013 kWh of energy every hour and 1 – 2- % of this is converted into wind energy. This occurs because the air at the equator is heated more than the rest of the earth. Hot air, being lighter than cold, rises to about 10km altitude and then spreads towards the north and south poles. The Coriolis force then causes the air movement to bend. The earth’s rotation diverts all the air in the Northern Hemisphere to the right and to the left in the southern hemisphere. Thus winds in the Northern Hemisphere tend to rotate in an anti-clockwise direction and those in the south rotate clockwise around low-pressure areas.
Winds are affected by the earth’s surface. Obstacles and roughness in particular slow it. It is these surface winds that are exploited during wind power generation.