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Water from a reservoir is conducted through large pipes the most reliable and dependable of several energy sources.
called penstocks to a powerhouse, where it is directed against Petroleum, coal, and hydropower are also used as energy sources
turbine blades that turn a shaft on an electric generator. A for electric power production. The electric utility companies are
rough approximation of the power that can be extracted from concerned that petroleum and natural gas are becoming increas-
the falling water can be made by multiplying the depth of the ingly expensive, and there are questions about long-term supplies.
water (in feet) by the amount of water flowing (in cubic feet per Hydropower has limited potential for growth, and solar energy is
second), then dividing by 10. The result is roughly equal to the prohibitively expensive today. Utility companies see two major en-
horsepower. ergy sources that are available for growth: coal and nuclear. There
are problems and advantages to each, but the utility companies feel
they must use coal and nuclear power until the new technologies,
NUCLEAR
such as solar power, are economically feasible.
Nuclear power plants use nuclear energy to produce electricity.
Energy is released as the nuclei of uranium and plutonium at-
oms split, or undergo a nuclear reaction called fission and form CONSERVING ENERGY
Conservation is not a way of generating energy, but it is a way
of reducing the need for additional energy consumption and
saves money for the consumer. Some conservation technologies
CONCEPTS Applied are sophisticated, while others are quite simple. For example, if
a small, inexpensive wood-burning stove were developed and
City Power used to replace open fires in the less-developed world, energy
Compare amounts of energy sources needed to produce consumption in these regions could be reduced by 50 percent.
electric power. Generally, 1 MW (1,000,000 W) will supply Many observers have pointed out that demanding more
the electrical needs of 1,000 people. energy while failing to conserve is like demanding more water
1. Use the population of your city to find how many to fill a bathtub while leaving the drain open. To be sure, con-
megawatts of electricity are required for your city. servation and efficiency strategies by themselves will not elimi-
2. Use the following equivalencies to find out how much nate demands for energy, but they can make the demands much
coal, oil, gas, or uranium would be consumed in one easier to meet, regardless of what options are chosen to provide
day to supply the electrical needs. the primary energy. Energy efficiency improvements have sig-
1 lb of coal nificantly reduced the need for additional energy sources. Con-
1 kWh = 0.08 gal of oil sider these facts, which are based primarily on data published
of electricity 9 cubic ft of gas by the U.S. Energy Information Administration:
0.00013 g of uranium
• Total primary energy use per capita in the United States in
Example 2003 was almost identical to that in 1973. Over the same
Assume your city has 36,000 people. Then 36 MW of 30 year period, economic output (gross domestic product,
electricity will be needed. How much oil is needed to produce or GDP) per capita increased 74 percent.
this electricity? • National energy intensity (energy use per unit of GDP) fell
43 percent between 1973 and 2002. About 60 percent of this
0.08 gal
1,000 kW
_ _ _ 69,120 or about
24 h

×
36 MW × × = decline is attributable to energy efficiency improvements.
MW day kWh 70,000 gal∙day

• If the United States had not dramatically reduced its
Since there are 42 gallons in a barrel,
energy intensity over the past 30 years, consumers and
gal
__ _ _ _ 1,666, or about businesses would have spent at least $430 billion more on
7,000
70,000 gal∙day
barrel
×

=

× =

42 gal∙barrel 42 day gal 2,000 barrel∙day energy purchases in 2003.

Even though the United States is much more energy-efficient to-
day than it was 25 years ago, the potential is still enormous for
additional cost-effective energy savings. Some newer energy
new elements (for the details, see chapter 13). The fissioning efficiency measures have barely begun to be adopted. Other
takes place in a large steel vessel called a reactor. Water is efficiency measures could be developed and commercialized in
pumped through the reactor to produce steam, which is used to coming years.
produce electrical energy, just as in the fossil fuel power plants. Much of the energy we consume is wasted. This statement
The nuclear processes are described in detail in chapter 13, and is not meant as a reminder to simply turn off lights and lower
the process of producing electrical energy is described in detail furnace thermostats; it is a technological challenge. Our use of
in chapter 6. Nuclear power plants use nuclear energy to pro- energy is so inefficient that most potential energy in fuel is lost
duce electricity, but some people oppose the use of this process. as waste heat, becoming a form of environmental pollution.
The electric utility companies view nuclear energy as one energy The amount of energy wasted through poorly insulated
source used to produce electricity. They state that they have no windows and doors alone is about as much energy as the
allegiance to any one energy source but are seeking to utilize United States receives from the Alaskan pipeline each year. It is
3-17 CHAPTER 3 Energy 77