Figure 2: Basic Wind Turbine
What is Wind Energy?
Wind Energy is energy that has been converted from the Earth’s natural
wind (kinetic energy) to usable form of electricity (mechanical energy) through
the use of a windmill, wind turbine, or wind machine.
What is a windmill?
A windmill is a kinetic device intended to capture the earth’s natural
wind and put it to work. A windmill is made of three primary parts, the rotor,
nacelle, and tower. The rotor is the most important part of the windmill; it
consists of the hub and the blades the turbine and attaches to the drive train.
The size of the rotor ultimately decides the overall potential performance and
cost of the windmill. The nacelle contains the drive train, the rotating parts
of the windmill, and sits atop the tower. The tower elevates the turbine off
the ground in order to allow the blades to catch the greatest amount of wind.
The longer the blades a turbine has the more energy it can potentially convert
because more torque can be generated by longer blades. Windmills can be indentified
in two ways, both relating to their potential energy output, by rotor diameter
and wattage.
Small Wind Turbine Nacelle and Rotor
Figure 2: Basic Wind Turbine
How is the energy converted?
The wind hits the blades inflicting a thrust/force on the turbine turning the
rotor, converting a finite amount of energy into rotational energy in the spinning
rotor. The spinning rotor is attached to a generator through wires/power lines;
the energy is converted once again to rotational energy in the shaft of the
motor of the generator. The motor spins a fan and work is accomplished, which
what we want.
How is the wind energy measured?
Energy is classified by power (watts), which is equal to voltage times current.
This represents the instantaneous rate of work when voltage moves through a
current. Windmills are often classified by their highest potential current that
could be produced at any given time, or the potential flow of electricity that
could be achieved by the turbine. A windmills energy classification is typically
measured in megawatts (MW).
What sizes do wind turbines come in?
Windmills can come in any size required, depending on the potential performance
the consumer is looking for. Small (household) windmills have a capacity of
about 10 kW with a rotor diameter ranging from 4 meters to 8.8 meters. Medium
windmills have a capacity of about 500 kW with a rotor diameter ranging from
10 to 15 meters. Large have a capacity of about 3 MW with a rotor diameter around
100 meters!
Figure 3: Representative size, height, and diameter of wind turbines
Images provided by Wind Energy Explained:
Theory Design and Application by J.F. Manwell, J.G. McGowan, and
A.L. Rogers