Environmental Engineering Reference
In-Depth Information
DID YOU KNOW?
Whenever wind energy is being considered as a possible source of renewable
energy it is important to consider the amount of land area required, accessibil-
ity to generators, and aesthetics.
WIND POWER
The terms
wind energy
and
wind power
describe the process by which the wind is
used to generate mechanical power or electricity. Wind turbines convert the kinetic
energy in the wind into mechanical power. This mechanical power can be used for
specific tasks (such as grinding grain or pumping water), or a generator can convert
this mechanical power into electricity (EERE, 2006a). We have been harnessing
the energy of the wind for hundreds of years. From old Holland to farms in the
United States, windmills have been used for pumping water or grinding grain; today,
the modern equivalent of a windmill—a wind turbine—can use the energy of the
wind to generate electricity. The blades of a wind turbine spin like aircraft propeller
blades. Wind turns the blades, which in turn spin a shaft connected to a generator to
produce electricity (Wind Energy EIS, 2009).
W
ind
t
urbine
t
ypes
Whether referred to as
wind-driven generators
,
wind generators
,
wind turbines
,
wind-
turbine generators
, or
wind energy conversion systems
, modern wind turbines fall
into two basic groups: the horizontal-axis wind turbine (HAWT), like the traditional
farm windmills used for water pumping, and the vertical-axis wind turbine (VAWT),
like the eggbeater-style, Darrieus rotor model, named after its French inventor, the
only vertical-axis machine with any commercial success. Wind hitting the vertical
blades, called
aerofoils
, generates lift to create rotation. No yaw (rotation about verti-
cal axis) control is needed to keep them facing into the wind. The heavy machinery in
the nacelle (cowling) is located on the ground. Blades are closer to the ground where
wind speeds are lower. Most large modern wind turbines are horizontal-axis turbines;
therefore, this type is highlighted and described in detail in this text.
H
orizontAl
-A
xis
W
ind
t
urbines
Wind turbines are available in a variety of sizes and power ratings. Utility-scale
turbines range in size from 100 kW to as large as several megawatts. Horizontal-axis
wind turbines typically have two or three blades. Downwind horizontal-axis wind
DID YOU KNOW?
Groups of wind turbines are located in what is called a
wind farm
or a
wind
park
(see
Figure 2.1
)
.
