All renewable energy (except tidal and geothermal power), ultimately comes from the sun.
The earth receives 1.74 x 1017 watts of power (per hour) from the sun.
About one or 2 percent of this energy is converted to wind energy (which is about 50-100 times more than the energy converted to biomass by all plants on earth.
Differential heating of the earthâ€™s surface and atmosphere induces vertical and horizontal air currents that are affected by the earthâ€™s rotation and contours of the land ïƒ WIND. ~ e.g.: Land Sea Breeze Cycle
Winds are influenced by the ground surface at altitudes up to 100 meters.
Wind is slowed by the surface roughness and obstacles.
When dealing with wind energy, we are concerned with surface winds.
A wind turbine obtains its power input by converting the force of the wind into a torque (turning force) acting on the rotor blades.
The amount of energy which the wind transfers to the rotor depends on the density of the air, the rotor area, and the wind speed.
The kinetic energy of a moving body is proportional to its mass (or weight). The kinetic energy in the wind thus depends on the density of the air, i.e. its mass per unit of volume. In other words, the "heavier" the air, the more energy is received by the turbine.
at 15Â° Celsius air weighs about 1.225 kg per cubic meter, but the density decreases slightly with increasing humidity.