create the same result. Frictional braking
systems and systems that use a combination of
means may also be used.
Wind and the environment
One obvious concern about increased wind
generating capacity would be the amount of
land that large wind farms would occupy. One
recent study suggested that wind farms would
need to occupy about 16,000 square miles to
produce 20% of the electrical demand for the
United States. Only a small percentage of this
land would be physically occupied, however.
About 95% of the land could serve dual use for
farming or ranching, in addition to wind
generation. Large wind turbines are also
known to produce some noise pollution, which
could be a detriment if located close to popu-
lated areas.
Hydrogen
To some, hydrogen is considered the ulti-
mate energy source. This is because hydrogen
is found in water, which covers about two-
thirds of the earth’s surface. It is also one of the
most common elements in the galaxy.
Therefore, hydrogen is considered inex-
haustible. A problem is that hydrogen rarely
Hydrogen: The first
and simplest
element on the
periodic table. It is
one of the most
common elements
in the galaxy.
114
Figure 5-18. The major parts of a horizontal wind turbine.
Blade
Nacelle
Wind
Nacelle
Generator Yaw drive
Yaw
brake
Blade
Pitch
actuator
Disc
brake
Anemometer/
wind vane
Gearbox
Chapter 5
Figure 5-17. Today’s wind generators are
usually designed with two or three blades for
maximum efficiency. This small three-blade
generator serves the needs of a single home,
supplementing other energy sources.