The Work of Wind and Deserts - The Changing Earth: Exploring Geology and Evolution - page 398

larger and more effi cient windmills ex-
clusively designed to generate electricity.
Denmark began using such windmills
as early as 1890, and other countries
soon followed suit. Interest in
electricity-generated windmills has
always mirrored the price of fossil
fuels. When the price of petroleum and
coal is low, it is cheaper to use these
fuels to generate electricity. When the
price of fossil fuels goes up, interest
in wind power also increases. Today,
wind power is an important source of
electricity, both in the United States
and elsewhere around the world, par-
ticularly in Europe. As wind turbine
technology has increased the effi ciency
of wind-generated electricity, the price
has decreased signifi cantly, so that wind
farms can now compete in many areas
with traditional fossil fuel-burning
power plants.
How do windmills produce elec-
tricity? Simply stated, wind turbines
(the term commonly used to describe
electricity-producing windmills) con-
vert the kinetic energy (the energy of
an object due to motion) of the wind
into mechanical power, in this case, the
generation of electricity. This electricity
is sent to the local power grid where it
is distributed throughout the area.
In order to be effective, numerous
wind turbines are clustered together
in wind farms that are located in areas
with relatively strong, steady winds.
The number of turbines on wind farms

can range from several to thousands,
as in California (Figure 2). In addition
to wind farms on land, wind farms
offshore are becoming more popu-
lar because they are out of sight and
people cannot hear the blades turning.
In fact, wind farms in the North Sea
already provide approximately 20% of
Denmark's energy needs. In the United
States, wind power production cur-
rently accounts for about 9% of the
total power produced by all means.
What are the advantages and dis-
advantages of wind power? First of all,
the wind is a free, renewable energy
source, so it cannot be used up. It
is also a clean source of energy that
doesn't pollute the water or atmo-
sphere, or contribute to greenhouse
gases. Thus, it reduces the consump-
tion of fossil fuels. The land on which
windmills are sited can still be used
for farming and ranching, thereby
increasing the productivity of the land
and providing an additional source of
income to the landowner who leases
the land to utilities. In addition, wind
farms can benefi t the local economy
of rural and remote areas by supplying
wind energy for local consumption.
There are some disadvantages to
wind-generated electricity. The major
disadvantage is that wind doesn't al-
ways blow with suffi cient strength to
be totally reliable, thereby necessitat-
ing backup generation. Furthermore,
good wind sites are frequently located

in remote areas, far from the areas
where large quantities of electricity
are needed, or in coastal areas, where
land is expensive and local residents
do not want large wind turbines as
neighbors. The initial start-up cost of
a wind farm is usually higher than the
cost of a conventional power plant.
However, as the cost of wind power
has decreased because of better tech-
nology, wind-generated electricity can
compete favorably with traditional
power plants in many areas. The “not-
in-my-backyard” opposition to wind
frames can make siting a wind farm
diffi cult. The major objection to wind
farms is the noise generated by the
turbines, although as the windmills
are built taller and the turbines are
more effi cient at noise reduction, that
is not the major concern it once was.
Of course, aesthetics still plays a role
in many people's objection to wind
farms, and the fact that some birds are
killed by the rotating blades is another
issue. Studies have indicated, however,
that the impact of wind turbines on
bird mortality and injury is less than
that of many other structures, such as
buildings, power lines, and communi-
cation towers.
As the price of fossil fuel continues
to rise, and our dependency on for-
eign sources of oil increases, the use of
a centuries-old staple, the windmill,
albeit modernized, will continue to
gain in popularity and use.

water table is usually far deeper than the channels of most
streams, so they cannot draw upon groundwater to replace
water lost to evaporation and absorption into the ground.
This type of drainage in which a stream's load is deposited
within the desert is called internal drainage and is common
in most arid regions.
Although most deserts have internal drainage, some
deserts have permanent through-flowing streams, such as
the Nile (see Chapter 12 Geo-Focus on page 307) and Niger
rivers in Africa, the Rio Grande and Colorado River in the
southwestern United States, and the Indus River in Asia.
These streams can flow through desert regions because

their headwaters are well outside the desert and water is
plentiful enough to offset losses resulting from evapora-
tion and infiltration. Demands for greater amounts of wa-
ter from the Colorado River for agriculture and domestic
use, however, are leading to increased salt concentrations
in its lower reaches and causing political problems be-
tween the United States and Mexico.

Wind
Although running water does most of the erosional work in
deserts, wind can also be an effective geologic agent capable