The Energy is Blowin’ in the Wind

Wind energy is electricity that is generated by the wind. Wind movement causes the turbine rotors to rotate and they turn the generator. No fuel is burned to generate the electricity. So the key to determining if a wind generation site can be used to generate electricity is the amount of Wind Resource that is available.

Every wind generation site is unique. The local topography and vegetation determine the low level wind shear factors. At higher altitudes wind may be less affected by the ground, but meteorological conditions can cause effects, such as the “Low Level Jet”.
Wind Resource Measurement

To determine the amount of electricity that can be generated, a long term wind study must be completed. This can take between 12 and 18 months.

At a height of 20 meters, wind measurement towers are available from most state Renewable Energy Program offices.

At a height of 150 – 250 meters, standard wind measurement towers are not tall enough.
The Force of the Wind

When air is moving, each of the tiny molecules of gas push a very small amount of force on everything they run into.

Billions and billions of molecules all hitting the same surface can produce a large force. If the wind speed is too low, the force is very small. If the wind speed is too high, like in a tornado or hurricane, then the wind force is so high that it can destroy things.

But, it is not this force that is useful in generating wind energy.
The Airfoil

Ancient Chinese attempted to sail through the air by attaching themselves to kites. The kite evolved into the airfoil shape over several centuries. Leonardo da Vinci, discovered and analyzed several of the basic principles of aerodynamics and physics.

Since the Wright Brothers Wright brothers made their first powered flight in 1903, the airfoil has been transformed into various configurations using advanced materials.

The airfoil is shaped so that the air traveling over one surface must go farther than the air traveling over the surface on the opposite side. The air that travels the longer surface is "stretched" so that the gas molecules are slightly farther apart. This generates a vacuum which "pulls" the airfoil toward that surface.

The rotor blades on a wind generation system are shaped like airfoils. The rotor blades are tilted at an angle, so the wind does not push on them. Instead, the air flows past the blade and a force is generated by the pull of the wind on one side of the airfoil.

This force causes the rotor blade to move and causes the rotor to rotate. The rotor is attached either directly or through a gearbox to the generator. So, as the wind moves, the force created by the wind motion, is applied to cause the generator to rotate and produce electricity.

The amount of force that is generated depends on the velocity of the wind. This is why the wind speed is the most important factor that determines whether the wind site can profitably produce electricity, or not.