15.3 Energy Resources

Reading StrategyIdentifying Main Ideas Copy the tablebelow. As you read, write the main idea foreach heading.

Key ConceptsWhat are the majornonrenewable andrenewable sourcesof energy?

How can energy resourcesbe conserved?

Vocabulary� nonrenewable

energy resources� fossil fuels� renewable energy

resources � hydroelectric

energy � solar energy � geothermal energy� biomass energy � energy conservation

Nonrenewable energyresources

Renewable energyresources

Conserving energy resources

Heading Main Idea

a. ?

b. ?

c. ?

From the alarm clock that wakes you up each morning to the light

that you turn off before you sleep, you depend on energy resources to

operate many different devices to get you through each day. Energy

resources can be classified as either renewable or nonrenewable.

Nonrenewable Energy ResourcesNonrenewable energy resources exist in limited quantities

and, once used, cannot be replaced except over the course of

millions of years. Nonrenewable energy resourcesinclude oil, natural gas, coal, and uranium. Such resources

are currently being used much faster than they can be

replaced, creating concern about how long they will last.

Oil, natural gas, and coal are known as fossil fuelsbecause they were formed underground from the remains

of once-living organisms. Currently, fossil fuels account for

the great majority of the world’s energy use. These fuels are

not distributed evenly throughout the world. For example,

about 60 percent of known oil supplies are located in a small

area in the Middle East. The United States has just 2 percent

of the world’s oil supplies but about 25 percent of the world’s

coal supplies. Fossil fuels are relatively inexpensive and are

usually readily available, but their use creates pollution.

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Figure 16 Crude oil is pumpedout of the ground or ocean floor.It is then refined and turned intogasoline, fuel oil, and otheroil products.

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FOCUS

Objectives15.3.1 Classify energy resources as

renewable or nonrenewable.15.3.2 Evaluate benefits and

drawbacks of different energysources.

15.3.3 Describe ways to conserveenergy resources.

Build VocabularyWord-Part Analysis Ask studentswhat words they know that contain the key word parts geo- and bio-.(Answers may include geology,geometry; biology, biography.) Askthem to give a definition of each wordpart. (geo- means “Earth” and bio-means “life.”)

Reading Strategya. Nonrenewable energy resourcesinclude oil, natural gas, and coal. They exist in limited quantities.b. Renewable energy resources includehydroelectric, solar, geothermal, wind,biomass, and nuclear fusion. c. Energy resources can be conserved by reducing energy needs and byincreasing energy efficiency.

INSTRUCT

Nonrenewable Energy ResourcesUse VisualsFigure 16 Have students examineFigure 16. Ask, What energy resourceis being extracted in the figure?(Crude oil) Does it require energy topump crude oil from undergroundand to process crude oil into moreuseful forms of fuel, such as gasoline?(Yes) If it requires energy to pump and process oil, then how can oil be a useful source of energy? (The amountof energy that the oil provides is greaterthan the energy required to extract it.)Of the forms of energy that youlearned in Section 1, what form of energy does the oil contain?(Chemical energy)Visual, Logical

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Reading Focus

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Section 15.3

Print• Reading and Study Workbook With

Math Support, Section 15.3• Math Skills and Problem Solving

Workbook, Section 15.3• Transparencies, Section 15.3

Technology• Interactive Textbook, Section 15.3• Presentation Pro CD-ROM, Section 15.3• Go Online, Science News, Energy and

energy resources

Section Resources

Energy 463

Renewable Energy ResourcesRenewable energy resources are resources that can be replaced in a rela-

tively short period of time. Most renewable energy resources originate

either directly or indirectly from the sun. The sun and Earth are con-

stantly releasing large amounts of energy. This energy can be used for

generating electric power, heating buildings or other purposes.

Renewable energy resources include hydroelectric, solar, geo-thermal, wind, biomass, and, possibly in the future, nuclear fusion. The

challenge for engineers and scientists is to find efficient ways to make

these energy resources inexpensive and convenient.

Hydroelectric Energy Energy obtained from flowing water is

known as hydroelectric energy. Hydroelectric energy is an indirect form

of solar energy. Energy from the sun causes evaporation of water, which

later falls back to Earth as precipitation. The water from this precipitation

often collects to form rivers. As river water flows downhill, its gravita-

tional potential energy is converted into kinetic energy. This kinetic

energy can be used to turn turbines that are connected to electric gener-

ators in a power plant, such as the one shown in Figure 17. The major

advantages of hydroelectric energy include its low cost to produce and

lack of pollution. Dams, however, cause a variety of environmental

problems. For example, dams hamper the run of fish upriver for

spawning. Also, in the United States, many of the most suitable sites for

hydroelectric plants are already in use.

World Energy Use

Which energy resources are most commonly usedaround the world? How is energy use changingover time? The table shows total world energy usein 2000 and 2007. Energy use can be measured inBritish thermal units, or Btu (1 Btu � 1055 J). Notethat petroleum includes oil and related fuels.

1. Using Tables What was the world’s largestsource of energy in 2000? In 2007?

2. Analyzing Data In general, how did usagechange from 2000 to 2007?

3. Graphing Make a circle graph of worldenergy use by source for the year 2007.

4. Analyzing Data What percentage of worldenergy use in 2007 was accounted for by fossil fuels?

5. Predicting How might total world energy usebe different in 2020? Explain.

Petroleum

Coal

Natural gas

Hydroelectric power

Nuclear fission

Other

2000

155.52

92.37

90.95

26.73

25.65

2.99

2007

173.87

132.47

111.21

29.64

27.06

5.32

World Energy Use (�1015 Btu)

Source

Figure 17 Hoover Dam was builtacross the Colorado River on theArizona-Nevada border. This 221-meter-tall structure can generateover 2 million kilowatts of power.Applying Concepts What type ofenergy conversion is involved in ahydroelectric plant?

Renewable EnergyResourcesIntegrate Earth ScienceWhile hydroelectric power itself is a cleanand renewable resource, hydroelectricdams block the regular flow of rivers,flooding areas upstream to create largereservoirs. Dam construction oftenreceives public support not only becauseit provides power, but also because itcreates lakes that provide recreationalopportunities. The reservoir creates anew aquatic ecosystem, but it alsodestroys the ecosystem that was therefor a long time before the dam was built.Have students use a library or theInternet to research the effects of damson landscapes and ecosystems. Havethem write a report arguing for oragainst the construction of large dams.Verbal, Portfolio

World Energy Use1. Petroleum in both years2. Each type of energy use increasedbetween 2000 and 2007.3. Students’ circle graphs should reflectthe following approximate percentagesof world energy use by source:petroleum (36%), coal (28%), naturalgas (23%), hydroelectric power (6%),nuclear fission (6%), other (1%).4. Approximately 87%5. Based on the trend between 2000and 2007, students will likely predictthat total world energy use will besignificantly higher in 2020 than it wasin 2007. They may also predict that thepercentage of energy resources in the“other” category (which includes mostrenewable energy resources) willincrease by 2020.Logical

For Extra HelpTell students to scan the data verticallyto answer Question 1 and horizontallyto answer Question 2. For Questions 3and 4, review the calculation of percent-ages. Tell students that they must firstfind the total world energy use for theyear 2007 by adding all the numbers in the right-hand column. Logical

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Energy 463

Customize for English Language Learners

Incorporating Personal NarrativesTell students a story about a time in your life when you were lacking in a commonlyavailable energy resource or a conveniencethat depends on energy resources (forexample, during a power outage or when your car broke down). Ask students specificquestions about how you could have changedyour behavior to deal with the situation,

for example, “What could I use for lights at night?” or “How could I get to work?”Encourage students to tell their own storiesabout similar situations. To close thediscussion, you may point out that some of the ways people deal with unusual oremergency conditions are also ways thatpeople could reduce energy use in everyday life.

Answer to . . .

Figure 17 Gravitational potentialenergy to kinetic energy and kineticenergy to electric energy

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Solar Energy The amount of energy from the sun that

reaches Earth in one hour is more than the amount of

energy used by the world’s population in a year. Sunlight

that is converted into usable energy is called solar energy.Passive solar designs use sunlight to heat a building without

using machinery. Sunlight passing through the windows of

a house may be absorbed by walls that then radiate thermal

energy to warm the house.

In an active solar energy system, sunlight heats flat col-

lection plates through which water flows. The heated water

may be used directly, or it may be used to heat the house.

Sunlight can also be converted into electrical energy by solar

cells, also known as photovoltaic cells, like those shown in

Figure 18A. Concentrating solar power (CSP) plants use mir-

rors to focus sunlight to produce electricity.

The benefits of solar energy depend on the climate. Solar

energy is nonpolluting, but for areas where cloudy days are

frequent, solar energy is less practical.

Geothermal Energy Geothermal energy is thermal

energy beneath Earth’s surface. In some regions, especially

near volcanoes, geothermal energy is used to generate elec-

ticity. The geothermal power plant in Figure 18B pumps

water into the ground, where it turns into steam. The steam

is then used to drive electric generators. Geothermal energy

is nonpolluting, but is not widely available.

Other Renewable Resources Sunlight causes plants to grow,

converting electromagnetic energy into chemical energy. The chemi-

cal energy stored in living things is called biomass energy. Biomass

can be converted directly into thermal energy. For example, many

people around the world burn wood or peat to heat their homes or for

cooking. Also, agricultural wastes such as corn stalks can be converted

into a high-energy alcohol fuel that can be added to gasoline for cars.

Wind energy is another renewable energy source. Wind turbines

convert the kinetic energy of wind into electrical energy. Wind energy

is actually a form of solar energy. Energy from the sun causes uneven

heating of air, which, in turn, causes differences in air pressure. Winds

blow from areas of higher pressure to areas of lower pressure.

A form of hydrogen is also the most likely raw material for another

future source of energy, nuclear fusion. The process of fusion will prob-

ably produce little pollution or radioactive waste. Scientists have been

working on sustained fusion for years, but many challenges remain.

What is biomass energy?

For: Articles on energy andenergy resources

Visit: PHSchool.com

Web Code: cce-2153

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Figure 18 Solar and geothermalenergy plants use renewableresources to generate electricity.A A concentrating solar power(CSP) plant uses solar cells toconvert sunlight into electricity. B A geothermal plant inCalifornia uses Earth’s thermalenergy to generate electricity. Comparing and ContrastingWhat are some similarities anddifferences between solar energyand geothermal energy?

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Simple Solar CellPurpose Demonstrate energyconversions and renewable resources.

Materials small solar array, smallmotor with fan, direct sunlight or brightlight source

Procedure Attach the wires from themotor to the solar array. Place the solararray in direct sunlight or under a brightlight source.

Expected Outcome The motor will spin and the fan blades will rotate. Askstudents to describe the energy trans-formations, starting with the light andending with the motion of the blades.(Electromagnetic energy from light is con-verted to electrical energy in the solar cell.The motor converts this electrical energyinto kinetic energy, which turns the fan.)Kinesthetic, Logical

Use Community ResourcesHave students contact the local electriccompany and ask what kind of powerplant(s) it uses. Have students ask if thecompany uses any renewable energyresources, such as wind, solar, orgeothermal energy. Interpersonal, Portfolio

Build Reading LiteracyCompare and Contrast Refer to page 226D in Chapter 8, whichprovides the guidelines for comparingand contrasting.

Have students compare and contrastrenewable energy resources. Ask, Howare all renewable energy sourcessimilar? (They can be replaced in a shorttime; most originate from the sun; most arenonpolluting.) Ask, Which renewableenergy sources are derived from thekinetic energy of natural materials?(Hydroelectric, wind)Logical

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Section 15.3 (continued)

Extreme Solar Energy The British-Americanphysicist Freeman Dyson is famous for hisinventive ideas related to the Search forExtraterrestrial Intelligence (SETI). In 1959,Dyson proposed a theoretical device, nowcalled a Dyson sphere, that an advancedcivilization could use to capture nearly all ofthe energy radiated from a star.

Dyson believed that while a moderatelytechnological civilization like our own is limited

to the energy resources found on our homeplanet, a highly advanced technologicalcivilization (particularly one capable of inter-stellar travel) would have more extreme energyneeds. Therefore, they would eventually comeup with a device similar to the Dyson sphere.Dyson suggested that scientists searching forextraterrestrial life should look for evidence ofDyson spheres because they would be suresigns of an advanced civilization.

Facts and Figures

Science News provides studentswith current information on energyand energy resources.

Wind farmEnormous wind farms like thisone in California can generate asmuch power as a large powerplant (without any air pollution).

Blades The shape and angle of theblades are designed to extract as muchenergy as possible from the horizontalmovement of the wind.

Wind TurbineWind turbines convert the kinetic energy in the horizontalmovement of wind into rotational energy of the turbine’srotor shaft. Rotational energy is then converted intoelectrical energy using an electric generator. The output of awind turbine depends on the turbine’s size and the wind’sspeed. Interpreting Diagrams What is the purpose of the gearbox?

Gearbox The rotorshaft itself rotatesfairly slowly at about20–30 revolutions perminute. The gearboxconverts this to arotation some 50 timesfaster—about 1500revolutions per minute.

Generator The shaft fromthe gearbox enters thegenerator, which convertsthe kinetic energy of theshaft into electricalenergy.

Windvane

The anemometermeasures windspeed.

A yaw ringchanges thedirection of the turbine.

Yaw drivemechanism

Rotor shaft

Winddirection

Direction ofrotation

Control unit Thiscomputer-operatedunit controls the yawdrive mechanism,ensuring that theturbine always facesdirectly into the wind.

Electrical energypasses to thelocal grid.

Energy 465

Wind TurbineHumans have used wind as a source ofpower for many centuries. Perhaps theearliest example is the use of sails topower ships. Windmills were used in theMiddle East and China to pump water or grind grains as early as 500 A.D. Theearliest windmills turned on a verticalaxis, rather than a horizontal axis as mostdo today. Windmills played an importantrole in the development of the AmericanWest, as they provided power to pumpwater from underground sources tosupport livestock and crops. The use ofwind turbines to generate electricitydeveloped in tandem with the increasinguse of electricity in the late nineteenthand early twentieth centuries. Today,wind provides less than one % of theelectric power used in the United States.However, proponents of wind powerestimate that wind could provide up to ten times our current total use of electricity.

Wind power is essentially a type of solarpower because wind is driven by unevenheating of air near Earth’s surface by thesun. This also means that wind is a freeand renewable resource. Because thereare no chemical or nuclear reactionsinvolved in generating electricity fromwind, wind power produces no pollution.

Interpreting Diagrams The purposeof the gearbox is to increase therotational speed of the shaft.Logical

For EnrichmentThe most extensive wind resources on Earth are found over the oceans.Have students research large offshorewind farms currently in use or in devel-opment. They may write a report orprepare a presentation for the classabout their findings.Verbal, Portfolio

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Energy 465

Answer to . . .

Figure 18 Both solar energy andgeothermal energy are renewableenergy resources that are nonpollutingand can be used to produce electricity orheat. The source of solar energy is thesun, while that of geothermal energy is heat from Earth. The factors thatinfluence their availability differ as well.

The chemical energystored in living things

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Section 15.3 Assessment

Reviewing Concepts1. List the major nonrenewable and

renewable sources of energy.

2. What could be done to make presentenergy resources last longer?

3. Why are coal, oil, and natural gas calledfossil fuels?

Critical Thinking4. Applying Concepts You are looking for the

best place to build a hydroelectric plant alonga river. Would you locate the plant along asteep or flat section of the river? Explain.

5. Comparing and Contrasting Howare passive and active solar energy systems different?

6. Applying Concepts Describe three waysthat you used energy resources today.

Conserving Energy ResourcesFossil fuel supplies may become increasingly scarce and expensive in

the future. An important way to make these energy resources last

longer is to use them more slowly. Energy resources can beconserved by reducing energy needs and by increasing the efficiencyof energy use. Finding ways to use less energy or to use energy more

efficiently is known as energy conservation.It’s easy to forget that the energy you use often comes at the

expense of resources that are being used up forever. People can reduce

the use of these resources by making energy-saving decisions, for

example turning off lights when they are not being used. Because con-

ventional cars consume an enormous amount of energy, the decisions

that people make about transportation are very important. Walking

or biking on short trips and carpooling can save considerable energy.

Using mass transportation, such as the streetcar shown in Figure 19,

can also reduce energy use.

Making appliances, cars, and even light bulbs more energy efficient

is a way of reducing energy use while still enjoying its benefits. Much

has already been done to make appliances more energy efficient. Light

bulbs have been developed that provide superior lighting at a lower

energy cost. The technology for further improvement, including more

fuel-efficient cars, is already known in many cases. However, the initial

cost of energy efficiency can be an obstacle for manufacturers and for

consumers. Energy-efficient purchases often cost more initially, but

can save money in fuel costs over time.

Figure 19 Mass transportationsystems include buses, trains, andstreetcars such as the one shownhere. Inferring How can the use of mass transportation save energy?

Writing to Persuade Suppose you are anenergy planner who is concerned about thepossibility of future shortages of electricity.Write a paragraph describing one or two pro-posals that you think would help to avoid thispotential problem.

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Conserving EnergyResources

Some students may think that energycomes from a specific source, such asfood or a power company. Point out thatobjects always have some gravitationalpotential energy (with respect to somereference point), and that any movingobject has kinetic energy. The forms ofenergy discussed in this section can beharnessed and distributed on a largescale, often by converting them toelectrical energy. Verbal

Build Science SkillsAnalyzing Data Have studentsexamine a monthly electricity bill to findthe energy usage. Show students thatkW-h � power � time � (work/time) �time � work. Explain that work has thesame units as energy. Ask students toconvert the usage from kilowatt-hoursto joules (1 kW-h � 1000 W-h �3600 s/h � 3.6 � 106 J).Logical, Portfolio

ASSESSEvaluate UnderstandingAsk students to state the fundamentaldifference between renewable andnonrenewable energy resources andthen list at least three examples of each.

ReteachHave each student review an energyresource. Have them work in pairs anddiscuss the pros and cons of the resourcethat they reviewed.

Encourage students to use a library or theInternet to research energy conservationand alternative energy resources.

If your class subscribesto the Interactive Textbook, use it toreview key concepts in Section 15.3.

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Section 15.3 (continued)

4. Steep, because the faster moving water hasmore kinetic energy and thus can generatemore power5. Passive solar systems convert sunlight tothermal energy without the use of machinery.Active solar systems use machinery to convertsunlight into thermal energy or electricity.6. Student answers may include turning on anelectric light, listening to the radio, taking ashower, using a computer, and so forth.

Section 15.3 Assessment

1. Nonrenewable: oil, natural gas, coal, anduranium; Renewable: solar, hydroelectric,wind, biomass, geothermal, and possiblynuclear fusion in the future2. Use nonrenewable energy resources moreslowly by reducing energy use and increasingenergy efficiency.3. They are each made from remains ofancient organisms.

Answer to . . .

Figure 19 By reducing the totalnumber of vehicles