Environmental Engineering Reference
In-Depth Information
FIGURE 2.1
Wind turbines at the Tehachapi Pass Wind Farm in California. Wind develop-
ment in the Tehachapi Pass began in the early 1980s, and this is one of the first large-scale
wind farms installed in the United States.
turbines have a turbine with the blades behind (downwind from) the tower. No yaw
control is needed because they naturally orient themselves in line with the wind;
however, these downwind HAWTs experience a shadowing effect, in that when a
blade swings behind the tower the wind it encounters is briefly reduced and the blade
flexes. Upwind HAWTs usually have three blades in front (upwind) of the tower.
These upwind wind turbines require a somewhat complex yaw control to keep them
facing into the wind. They operate more smoothly and deliver more power and thus
are the most commonly used modern wind turbines. The largest machine has blades
that span more than the length of a football field, stands 20 building stories high, and
produces enough electricity to power 1400 homes.
Inside the HAWT
Basically, a horizontal-axis wind turbine consists of three main parts: a turbine, a
nacelle (the cover housing that houses all of the generating components in a wind tur-
bine, including the generator, gearbox, drive train, and brake assembly), and a tower.
Several other important parts are contained within the tower and nacelle, including
anemometer, blades, brake, controller, bear box, generator, high-speed shaft, low-
speed shaft, pitch, rotor, tower, wind direction, wind vane, yaw drive, and yaw motor
(see
Figure 2.2
)
.
