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Science and Society

Use Wind Energy?
illions of windmills were installed farms,” which are large clusters of intercon- Oregon, and Wyoming. Other states with
Min rural areas of the United States nected wind turbines connected to a utility a strong wind power potential include
between the late 1800s and the late 1940s. power grid. Kansas, Montana, Nebraska, Oklahoma,
These windmills used wind energy to pump Many areas of the United States have Iowa, Colorado, Michigan, and New York.
water, grind grain, or generate electricity. a high potential for wind power use. All of these states, in fact, have a greater
Some are still in use today, but most were North Dakota, South Dakota, and Texas wind energy potential than California.
no longer needed after inexpensive electric have enough wind resources to provide
power became gen erally available in rural electricity for the entire nation. Today, only
QUESTIONS TO DISCUSS
areas of the country. California has extensively developed wind
In the 1970s, wind energy began mak- farms, with more than 13,000 wind tur- Discuss with your group the following
ing a comeback as a clean, renewable energy bines on three wind farms in the Altamont questions concerning wind power:
alternative to fossil fuels. The windmills of Pass region (east of San Francisco),
1. Why have electric utilities not used
the past were replaced by wind turbines of Techachapi (southeast of Bakersfield), and
much wind power as an energy source?
today. A wind turbine is usually mounted San Gorgonio (near Palm Springs). With a
2. Should governments provide a tax
on a tower, with blades that are rotated total of 2,361 MW of installed capacity in
break to encourage people to use wind
by the wind. This rotary motion drives a California, wind energy generates enough
power? Why or why not?
generator that produces electricity. A loca- electricity to more than meet the needs of
tion should have yearly wind speeds of at a city the size of San Francisco. The wind 3. What are the advantages and disad-
least 19 km/h (12 mi/h) to provide enough farms in California have a rated capacity vantages of using wind power in place
wind energy for a turbine, and a greater that is comparable to two large coal-fired of fossil fuels?
yearly average means more energy is avail- power plants but without the pollution 4. What are the advantages and
able. Farms, homes, and businesses in these and limits of this non renewable energy disadvantages of the government
locations can use smaller turbines, which source. Wind energy makes economic as building huge wind farms in North
are generally 50 kW or less. Large tur- well as environmental sense, and new wind Dakota, South Dakota, and Texas to
bines of 500 kW or more are used in “wind farms are being developed in Minnesota, supply electricity for the entire nation?

A Sea Breeze
CONCEPTS Applied

Why the Beach Is Cooler
Low pressure
Adjacent areas of the surface can have different High pressure
temperatures because of different heating or cooling rates.
The difference is very pronounced between adjacent areas
of land and water. Under identical conditions of incoming
solar radiation, the temperature changes experienced by
the water will be much less than the changes experienced
by the adjacent land. There are three principal reasons for B Land Breeze
this difference: (1) The specific heat of water is about five
times the specific heat of soil. This means that it takes
more energy to increase the temperature of water than it
does for soil. Equal masses of soil and water exposed to High pressure
sunlight will result in the soil heating about 5°C while the
Low pressure
water heats 1°C from absorbing the same amount of solar
radiation. (2) Water is a transparent fluid that is easily
mixed, so the incoming solar radiation warms a body of
water throughout, spreading out the heating effect. But
incoming solar radiation on land warms a relatively thin
layer on the top, concentrating the heating effect. (3) The
FIGURE 22.10 The land warms and cools more rapidly than an
water is cooled by evaporation, which helps keep a body
adjacent large body of water. (A) During the day, the land is warmer,
of water at a lower temperature than an adjacent landmass
and air over the land expands and is buoyed up by cooler, denser air
under identical conditions of incoming solar radiation.
from over the water. (B) During the night, the land cools more rapidly
than the water, and the direction of the breeze is reversed.
22-11 CHAPTER 22 The Atmosphere of Earth 551