ENERGY SOURCES
reflect
Imagine a car that could travel more than 200 miles
using only one gallon of gas. Does this seem like a car of
the future? Automakers are in the process of producing
such an automobile. (In fact, a prototype model has
been around since 2002.) This lightweight car would use
much less gasoline than any cars currently on the road.
Why is it important to consume fewer resources such
as gasoline?
Gasoline is a source of energy
There are two main sources of energy.
for cars.
We get energy from many sources on Earth. Energy is
the ability to do work. We use it to heat our homes, light
our lamps, and power our cars and computers. We call these sources energy resources.
The supply of some energy resources is limited. Nature cannot
make them as quickly as we use them. These are nonrenewable
resources. Once a nonrenewable energy resource is used up, it is
no longer available to us. The gasoline we use to power most cars
is a nonrenewable resource.
Blowing air moves
these windmills,
or turbines. As the
turbines move, they
generate electricity.
Nature makes other energy resources more quickly than we
use them. Their supply is practically unlimited! These renewable
resources include sunlight, wind, and water. Even on cloudy days,
the Sun sends thousands of times more energy to Earth than
humans use. As the Sun rises in the sky each day, the supply of
solar power is renewed. Similarly, winds are continually blowing
and water is continually flowing around the planet. We can use the
energy from moving air and water to produce electricity to power
our electric devices.
Fossil fuels are nonrenewable.
Humans get much of their energy by burning coal, oil, and
natural gas. We call these energy resources fossil fuels because
they are formed from plants and animals that died millions of
years ago. Because fossil fuels take millions of years to form, they are nonrenewable
energy resources. Eventually, we will use them all up.
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ENERGY SOURCES
Fossil fuels have many advantages. They are
relatively inexpensive to obtain and use. They produce
large amounts of energy when burned. They are
nonrenewable, yet they are still plentiful. Scientists
estimate there are still hundreds of billions of tons of
coal and hundreds of billions of barrels of oil remaining
on Earth.
Fossil fuels also have many disadvantages. Because
they are nonrenewable, we cannot rely on them
indefinitely. Some scientists estimate that within the
We burn fossil fuels at power
next 50–100 years, our supplies will run out. Burning
plants. The energy released
fossil fuels also releases pollutants into the air. One
by the fuels as they burn is
of these pollutants is carbon dioxide, a gas that traps
converted into electricity and sent
heat at Earth’s surface. Scientists agree that adding
to homes and other buildings.
carbon dioxide to Earth’s atmosphere is a cause of
global warming. It is also very difficult to remove
some fossil fuels from Earth without damaging the environment
global warming: the
from the mining and drilling that takes place. For example, as
increase in Earth’s
we move oil through pipes and on ships, it sometimes spills.
average temperature
Oil can also leak from our vehicles. These accidental spills can
over time
cause lots of damage to wildlife and the environment. So can
improperly disposing of oil—never dump oil down a drain!
Nuclear power is a nonrenewable energy source.
All matter is made up of tiny particles held together by forces called bonds. Humans can
break these bonds to release large amounts of energy called nuclear power.
One of the most important advantages of nuclear
power is that it does not produce much air pollution
or contribute to global warming. (Most of the gas
released from a nuclear power plant is water vapor.)
The fuel needed to produce nuclear power is relatively
inexpensive, and it releases much more energy than
fossil fuels. However, nuclear plants are expensive to
build and maintain. Although they do not pollute the
air, they produce large amounts of dangerous waste
that is not easy to store or get rid of. Nuclear power is
also nonrenewable—we use up the fuel more quickly
than nature can make it.
Between 15 and 20% of the
world’s electricity is produced at
nuclear power plants.
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ENERGY SOURCES
look out!
Nuclear power plants are dangerous
because they contain radioactive
materials. When a substance is
radioactive, its particles are breaking
apart. These particles can damage
nearby organisms.
When some people think of nuclear energy,
they remember terrible accidents that have
happened at nuclear power plants. In 1986,
a large nuclear power plant in Chernobyl,
Ukraine, released dangerous materials into
the surrounding environment. Many plants
and animals—including people—died or were
seriously injured. In 2011, an earthquake caused
the release of dangerous materials at a nuclear
plant in Fukushima, Japan. Nuclear power plants
in the United States and other countries are
regulated and inspected routinely. Still, the risk of
terrible accidents causes some people to oppose
nuclear energy.
Renewable energy resources can replace
nonrenewable ones.
In the United States, we use many more
nonrenewable energy resources than renewable
ones. In the past few years, energy use from several renewable energy resources has
greatly increased. Let’s take a look at some of the most commonly used renewable energy
resources.
This solar panel
collects and stores
sunlight. The
energy is then
used to power this
streetlight.
• Solar Power: Sunlight is probably the most important energy
resource on Earth. It warms the planet and provides plants
with the energy they need to make food. Humans can also use
sunlight to heat buildings and power machines. Today, many
scientists are working to find more and better uses for solar
power. Unlike most energy sources, solar power does not
produce air or water pollution. Although the Sun shines only part
of the time, batteries allow us to store solar energy to use later.
However, solar panels are expensive. The process of making
them can produce harmful waste, and old solar panels can be
difficult to safely dispose of.
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ENERGY SOURCES
• Geothermal: The Sun is Earth’s main source
of energy. However, our planet also produces
its own energy deep beneath the surface.
We call this geothermal energy. (Geo- means
“Earth” and thermal means “heat.”) Geothermal
energy is a clean energy source that produces
little waste. Geothermal plants are relatively
inexpensive to run, and they can generate power
around the clock. However, the initial cost of
building a geothermal plant is high, and they
can exist only where lots of Earth’s heat rises to
the surface—like near hot springs or geysers.
Additionally, geothermal energy is not easy
to transport.
Some geothermal energy comes
from warm water and rock near
Earth’s surface. Other energy
comes farther down, from extremely
hot, molten rock (magma).
• Hydropower: Hydroelectric plants use the energy of flowing
water as it moves downstream. (Hydro- means “water.”) The
water spins turbines to produce electricity. Dams are often
built near hydroelectric plants. The dams control the flow
of water—the dams can be shut off if power is not needed.
Hydropower is a clean energy source that does not pollute
the environment. Yet, dams are expensive to build and
maintain. They can cause flooding and disrupt the surrounding
ecosystem by slowing or even stopping the flow of water in
a river. In addition, power plants sometimes release heated
water back into the ecosystem. Plants and animals living
downstream of the dam may not be able to adapt to these
changes.
This dam on Lake
Travis produces
hydroelectric power in
central Texas.
• Wind: Like flowing water, blowing air can spin turbines to
produce electricity. These energy resources convert the
motion, or kinetic energy, of natural processes into electrical
energy we can use. Also like hydropower, using wind energy
does not produce pollution. However, wind turbines can be
noisy and expensive to build. As they spin in the air, they can
harm birds flying nearby.
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ENERGY SOURCES
• Biomass: Biomass refers to living or recently living organisms we can use as energy
resources. For example, corn plants are converted into a fuel called ethanol that can
replace gasoline in cars. Biomass is a cheap resource that can be made from many
common waste products. Unlike fossil fuels, biomass is renewable—we can grow new
plants quickly. However, burning biomass releases several harmful pollutants into the
air. It also releases less energy than burning the same amount of fossil fuels.
How can we manage our energy resources?
We cannot rely on nonrenewable energy resources forever. It is important to find ways to
switch to renewable energy resources. Using more renewable resources is only part of a
smart energy plan. In fact, a smart energy plan has at least three parts.
Have you ever seen this symbol? It stands for Reduce, Reuse,
and Recycle. To reduce our dependence on energy resources,
we can use fewer of them—for example, a person could walk or
ride a bike instead of drive a car. When we reuse and recycle
resources instead of throwing them away, we produce less
waste. We also reduce our need for new energy resources.
what do you think?
How can you apply the ideas of Reduce, Reuse, and Recycle to your own life? Think of
3–5 ways you can change your behavior to use fewer energy resources. How can you
encourage others in your community to conserve, or use fewer energy resources?
Scientists in the Spotlight: Dr. Stephen Chu
The goal of the United States Department of Energy is to focus
on America’s energy challenges for the present and the future.
The current U.S. Secretary of Energy, Dr. Stephen Chu, helps
carry out this goal. One of his main jobs is to lead the push
to replace nonrenewable and polluting energy resources with
renewable and clean energy resources. His other jobs include
reducing America’s dependence on oil from other countries and
addressing the role of energy use on climate change.
Dr. Chu was chosen for this position because of his scientific
background. In 1997, Dr. Chu won the Nobel Prize in physics.
He has taught physics at the University of California and
Stanford University. He was also the director of alternative and
renewable energy at the Lawrence Berkeley National Lab.
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ENERGY SOURCES
What do you know?
Study the photographs of the energy resources below. Identify each energy resource
as renewable or nonrenewable. Then, list two advantages and two disadvantages for
each resource.
Energy Source
Solar
Renewable/
Nonrenewable
Advantages
Disadvantages
Biomass
Coal
Nuclear
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ENERGY SOURCES
connecting with your child
Developing an Energy Plan
To help your child learn more about energy
sources, investigate different conservation
practices available to manage your energy
resources. First, evaluate your current use
of energy resources: which renewable and
nonrenewable energy resources do you
use in different aspects of your life? Next,
work with your child to create a plan for your
home, school, or community to conserve
energy resources and balance your use of
renewable and nonrenewable resources.
When developing your energy plan, identify
how you can lower your dependence on
fossil fuels and set reasonable goals.
Encourage your child to develop a threestep plan consisting of a short-term goal, a
medium-term goal, and a long-term goal.
The short-term goal may include common
energy saving methods such as reduce,
reuse, and recycle. This may include turning
off lights and appliances when not in use.
Here are some questions to discuss with
your child:
• What are ways that you can manage
your energy usage?
• How can one person affect energy
conservation in a community and in the
world?
• What are ways that you can replace
nonrenewable energy resources with
renewable ones?
• Consider the different energy sources
that you use:
• What are the advantages of each
source?
• What are the disadvantages of each
source?
Your medium-term goals may be to create a
plan for saving energy around the home—
for example, by replacing old appliances
with energy-efficient ones. Long-term
goals may apply to your whole community.
For example, your child may begin by
investigating the ways that your community
uses energy. Then, your child may write a
letter to your local government to articulate
concerns and identify ways to conserve
energy resources in the community.
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