How a wind-turbine generator works
Regardless of design, all wind generators work essentially the same
way. They all have some type of blades that capture the force of the wind.
Unlike the windmills of previous eras, most modern wind generators are
of a two- or three-blade design. See Figure 5-17. This is due to research
that indicates multiple blades actually capture less wind than two- or
three-bladed designs. The reason is that, every time a blade cuts through
the air, it creates some turbulence or swirling air that opposes the penetra-
tion of the next blade. Wind turbines that have fewer blades actually allow
the turbulence to stabilize before the next blade approaches.
Once the wind energy is converted to mechanical power by the blades,
it is transferred to a gearbox for conditioning. The gearbox steps up the
revolutions per minute (rpm) of the mechanical power and then transfers
the power to spin the generator. The nacelle houses the gearbox, the
generator, and a variety of equipment necessary to keep the wind turbine
properly positioned into the wind and spinning at a safe speed. See
Figure 5-18.
When it comes to wind generation, increased wind speed is generally
a good thing, but only to a point. A wind generator spinning at excessive
speeds creates undue stress on the machine. Therefore, all wind genera-
tors must be created with a means of slowing themselves to prevent over-
spin. This can be done by feathering the pitch of the blades so they do not
catch as much wind or by banking the wind turbine out of the wind to
Wind turbine: A
propeller driven by
the wind and
connected to a
generator. The
wind makes it turn
the generator,
which produces
electricity.
Wind velocity
profile: Data char-
acterizing the
number of
expected hours of a
given wind speed
for a particular
location.
Renewable and Inexhaustible Energy Sources 113
Figure 5-16. Wind farms make use of many high-capacity wind turbines to
generate significant amounts of electrical energy. (Shell Wind Energy)
Nacelle: An enclo-
sure that houses
the gearbox, the
generator, and a
variety of equip-
ment necessary to
keep a wind
turbine properly
positioned into the
wind and spinning
at a safe speed.
G R E E N T E C H
Although energy is
used to build wind
turbines and install
them in wind farms,
the energy gained
by using the turbines
pays for the
construction and
installation in under
a year on average.