LIVING IN THE ENVIRONMENT, 18e
G. TYLER MILLER • SCOTT E. SPOOLMAN
16
Energy Efficiency and
Renewable Energy
©©Cengage
CengageLearning
Learning2015
2015
Core Case Study: The Astounding
Potential for Wind Power in the U.S.
• Wind energy – wind farms convert to
electrical energy
• Wind power is inexhaustible
• Could meet electricity needs of the lower
48 states
– Texas and California are top producers
© Cengage Learning 2015
Gearbox
Electrical
generator
Power cable
Wind turbine
Fig. 16-1a, p. 402
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Fig. 16-1b, p. 402
16-1 Why Is Energy Efficiency an
Important Energy Resource?
• Improvements in energy efficiency could
save at least a third of the energy used in
the world and up to 43% of the energy
used in the United States
• We have a variety of technologies for
sharply increasing the energy efficiency of
industrial operations, motor vehicles,
appliances, and buildings
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We Use Energy Inefficiently
• Energy efficiency
– How much useful work we get from each unit
energy
• Advantages of reducing energy waste
– Usually the cheapest way to provide more
energy
– Reduces pollution and degradation
– Slows global warming
– Increases economic and national security
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We Use Energy Inefficiently (cont’d.)
• Four widely used devices that waste
energy
– Incandescent light bulb
– Motor vehicle with internal combustion engine
– Nuclear power plant
– Coal-fired power plant
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Energy Inputs
System
Outputs
9%
7%
41%
85%
U. S.
economy
43%
8%
3%
Nonrenewable fossil fuels
Nonrenewable nuclear
Renewable (hydropower,
geothermal, wind, solar,
biomass)
Useful energy
Petrochemicals
Unavoidable energy
loss
Energy waste
Fig. 16-2, p. 403
Solutions
Improving Energy Efficiency
Prolongs fossil fuel supplies
Reduces oil imports and
improves energy security
Very high net energy yield
Low cost
Reduces pollution and
environmental degradation
Buys time to phase in
renewable energy
Creates local jobs
Fig. 16-4, p. 404
We Can Improve Energy Efficiency in
Industry and Utilities
• Cogeneration
– Combined heat and power (CHP)
– Two forms of energy from same fuel source
• Replace energy-wasting electric motors
• Recycle materials
• Switch from low-efficiency incandescent
lighting to higher-efficiency fluorescent and
LED lighting
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Case Study: Saving Energy and Money
with a Smarter Electrical Grid
• Current electrical grid system – outdated
and wasteful
• Smart grid
– Ultra-high-voltage
– Super-efficient transmission lines
– Digitally controlled
– Responds to local changes in demand and
supply
– Easier to buy renewable energy
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We Can Improve Energy Efficiency and
Save Money in Transportation
• Hidden prices in gasoline
– Should be $12/gallon
– Car manufacturers and oil companies lobby to
prevent laws to raise fuel taxes
• Build or expand mass transit and high
speed rail
• Encourage biking
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More Energy-Efficient Vehicles Are on the
Way
•
•
•
•
•
Superefficient and ultralight cars
Gasoline-electric hybrid car
Plug-in hybrid electric vehicle
Energy-efficient diesel car
Electric vehicle with a fuel cell
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Conventional hybrid
Fuel tank
Plug-in hybrid
Fuel tank
Battery
Battery
Internal
combustion
engine
Transmission Electric motor
Internal
combustion
engine
Transmission Electric motor
Stepped Art
Fig 16-6, p. 406
We Can Design Buildings That Save
Energy and Money
• Green architecture
• Living or green roofs
– With specially designed soil and vegetation
• Superinsulation
– No need for heating system
• U.S. Green Building Council’s Leadership
in Energy and Environmental Design
(LEED)
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© Cengage Learning 2015
Fig. 16-7, p. 408
We Can Save Money and Energy in
Existing Buildings
• Conduct an energy audit:
– Insulate and plug leaks
– Use energy-efficient windows
– Stop other heating and cooling losses
– Heat houses more efficiently
– Use energy-efficient appliances
– Use energy-efficient lighting
– Use motion sensors to turn lights on and off
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Fig. 16-9, p. 410
Attic
• Hang reflective foil near
roof to reflect heat.
• Use house fan.
• Be sure attic insulation is
at least 30 centimeters
(12 inches).
Bathroom
• Install water-saving toilets,
faucets, and shower heads.
• Repair water leaks promptly.
Kitchen
• Use microwave rather than
stove or oven as much as
possible.
• Run only full loads in
dishwasher and use low- or
no-heat drying.
• Clean refrigerator coils
regularly.
Basement or utility room
• Use front-loading clothes washer. If possible run only full loads with warm or
cold water.
• Hang clothes on racks for drying.
• Run only full loads in clothes dryer and use lower heat setting.
• Set water heater at 140° if dishwasher is used and 120° or lower if no
dishwasher is used.
• Use water heater thermal blanket.
• Insulate exposed hot water pipes.
• Regularly clean or replace furnace filters.
Outside
Plant deciduous trees to block
summer sun and let in winter
sunlight.
Other rooms
• Use compact fluorescent
lightbulbs or LEDs and avoid
using incandescent bulbs
wherever possible.
• Turn off lights, computers, TV,
and other electronic devices
when they are not in use.
• Use high efficiency windows;
use insulating window covers
and close them at night and
on sunny, hot days.
• Set thermostat as low as you
can in winter and as high as
you can in summer.
• Weather-strip and caulk doors,
windows, light fixtures, and
wall sockets.
• Keep heating and cooling
vents free of obstructions.
• Keep fireplace damper closed
when not in use.
• Use fans instead of, or along
with, air conditioning.
Stepped Art
Fig. 16-10, p. 411
Why Are We Still Wasting So Much Energy
and Money?
• Energy remains artificially cheap
– Government subsidies
– Tax breaks
– Prices don’t include true cost
• Few large and long-lasting incentives
– Government rebates
– Low-interest loans
• Lack of education
© Cengage Learning 2015
We Can Use Renewable Energy to
Provide Heat and Electricity
• Renewable energy
– Solar energy
– Geothermal energy
• Renewable energy will be cheaper if we
eliminate:
– Inequitable subsidies
– Inaccurate prices
– Artificially low pricing of nonrenewable energy
© Cengage Learning 2015
Available Energy Flow (exajoules per year)
World energy
use (2010)
527
Direct
solar
>1,000
Wind
600
500
Geothermal
Biomass
Hydropower
Ocean
<250
50
<1
Fig. 16-11, p. 412
16-3 What Are the Advantages and
Disadvantages of Solar Energy?
• Passive and active solar heating systems
can heat water and buildings effectively
• The costs of using direct sunlight to
produce high-temperature heat and
electricity are coming down
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We Can Heat Buildings and Water with
Solar Energy
• Passive solar heating system
– Absorbs and stores heat from the sun directly
within a well-insulated structure
• Active solar heating system
– Captures energy from the sun in a heatabsorbing fluid
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Trade-Offs
Passive or Active Solar Heating
Advantages
Disadvantages
Net energy is
moderate (active)
to high (passive)
Need access to sun
60% of time during
daylight
Very low
emissions of CO2
and other air
pollutants
Sun can be blocked
by trees and other
structures
Very low land
disturbance
High installation and
maintenance costs
for active systems
Moderate cost
(passive)
Need backup system
for cloudy days
Fig. 16-14, p. 415
We Can Cool Buildings Naturally
• Technologies available
– Open windows when cooler outside
– Use fans
– Superinsulation and high-efficiency windows
– Overhangs or awnings on windows
– Light-colored roof
– Geothermal pumps
© Cengage Learning 2015
We Can Concentrate Sunlight to Produce
High-Temperature Heat and Electricity
• Solar thermal systems
– Collect sunlight to boil water, generate
electricity
– 1% of world deserts could supply all the
world’s electricity
– Require large amounts of water
• Wet cooling
• Dry cooling
• Low net energy yields
© Cengage Learning 2015
Fig. 16-15, p. 416
Trade-Offs
Solar Thermal Systems
Advantages
Disadvantages
High potential
for growth
Low net energy
and high costs
No direct
emissions of CO2
and other air
pollutants
Lower costs with
natural gas
turbine backup
Source of new
jobs
Needs backup or
storage system
on cloudy days
Can disrupt desert
ecosystems
Fig. 16-16, p. 416
We Can Use Solar Cells to Produce
Electricity
• Photovoltaic (PV) cells
– Convert solar energy to electric energy
• Design of solar cells
– Sunlight hits cells and releases electrons into
wires
• What are the benefits of using solar cells?
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We Can Use Solar Cells to Produce
Electricity (cont’d.)
• Key problems
– High cost of producing electricity
– Need to be located in sunny desert areas
– Fossil fuels used in production
– Solar cells contain toxic materials
• Cost could drop with:
– Mass production and new designs
– Government subsidies and tax breaks
© Cengage Learning 2015
Fig. 16-18, p. 418
Fig. 16-19, p. 418
Trade-Offs
Solar Cells
Advantages
Disadvantages
Medium net
energy yield
Need access to sun
Little or no direct
emissions of CO2
and other air
pollutants
Easy to install,
move around,
and expand as
needed
Competitive cost
for newer cells
Some designs have
low net energy yield
Need electricity
storage system or
backup
Costs high for older
systems but
dropping rapidly
Solar-cell power
plants could disrupt
desert ecosystems
Fig. 16-21, p. 419
16-4 What Are the Advantages and
Disadvantages of Using Hydropower
• We can use water flowing over dams, tidal
flows, and ocean waves to generate
electricity
– However, environmental concerns and limited
availability of suitable sites may limit the use
of these energy resources
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We Can Produce Electricity from Falling
and Flowing Water
• Hydropower
– Uses kinetic energy of moving water
– Indirect form of solar energy
– World’s leading renewable energy source
used to produce electricity
• What are the advantages and
disadvantages?
• Micro-hydropower generators: floating
turbines
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Trade-Offs
Large-Scale Hydropower
Advantages
Disadvantages
High net energy
yield
Large land
disturbance and
displacement of
people
Large untapped
potential
Low-cost
electricity
Low emissions of
CO2 and other air
pollutants in
temperate areas
High CH4 emissions
from rapid biomass
decay in shallow
tropical reservoirs
Disrupts downstream
aquatic ecosystems
Fig. 16-22, p. 420
We Can Use Tides and Waves to Produce
Electricity
• Produce electricity from flowing water
– Ocean tides and waves in coastal bays and
estuaries
• Power systems are limited
– Few suitable sites
– High costs
– Equipment damaged by storms and corrosion
© Cengage Learning 2015
16-5 What Are the Advantages and
Disadvantages of Using Wind Power?
• When we include the environmental costs
of using energy resources in their market
prices, wind power is the least expensive
and least polluting way to produce
electricity
© Cengage Learning 2015
Using Wind to Produce Electricity Is an
Important Step toward Sustainability
• Tall, long-blade turbines can extract more
energy from the wind
• Rapidly growing power source
– U.S., Europe, and China
– Future is offshore wind farms
• Wind power has potential to produce 40
times of the world’s current electricity used
© Cengage Learning 2015
Using Wind to Produce Electricity Is an
Important Step (cont’d.)
• Wind is abundant, widely distributed, and
inexhaustible
• High net energy yield
• Drawbacks:
– Largest potential areas are usually rural
– Winds can die down – need backup power
source
© Cengage Learning 2015
Trade-Offs
Wind Power
Advantages
Disadvantages
High net energy
yield
Needs backup or
storage system when
winds die down
Widely available
Low electricity
cost
Little or no direct
emissions of CO2
and other air
pollutants
Easy to build
and expand
Visual pollution for
some people
Low-level noise
bothers some people
Can kill birds if not
properly designed
and located
Fig. 16-25, p. 423
16-6 Advantages and Disadvantages of
Using Biomass as an Energy Source
• Solid biomass is a renewable resource for
much of the world’s population, but
burning it faster than it is replenished
produces a net gain in atmospheric
greenhouse gases
© Cengage Learning 2015
16-6 Advantages and Disadvantages of
Biomass as an Energy Source (cont’d.)
• We can use liquid biofuels derived from
biomass to lessen our dependence on oilbased fuels, but creating biofuel
plantations can:
– Degrade soil and biodiversity
– Increase greenhouse gas emissions
– Lead to higher food prices
© Cengage Learning 2015
We Can Produce Energy by Burning Solid
Biomass
• Biomass
– Plant materials and animal waste we can burn
or turn into biofuels
• Production of solid mass fuel
– Plant fast-growing trees; biomass plantations
– Collect crop residues and animal manure
• What are the advantages and
disadvantages of biomass energy?
© Cengage Learning 2015
Trade-Offs
Solid Biomass
Advantages
Disadvantages
Widely available
in some areas
Contributes to
deforestation
Moderate costs
Medium net
energy yield
Clear-cutting can
cause soil erosion,
water pollution, and
loss of wildlife habitat
No net CO2
increase if
harvested,
burned, and
replanted
sustainably
Can open
ecosystems to
invasive species
Plantations can
help restore
degraded lands
Increases CO2
emissions if harvested
and burned
unsustainably
Fig. 16-26, p. 424
Case Study: Is Biodiesel the Answer?
• Biodiesel
– Produced from vegetable oil
– European Union countries produce 95% of
the world’s biodiesel
• Crops require large amounts of land
• Production requires fossil fuels
© Cengage Learning 2015
Case Study: Is Ethanol the Answer?
• Ethanol
– Can be made from sugarcane, corn,
switchgrass, and various wastes
– United States largest producer
• Made from corn; low net energy yield
– Brazil second
• Sugarcane has medium net energy yield
• Cellulosic ethanol
– Produced from cellulose
© Cengage Learning 2015
Case Study: Is Ethanol the Answer?
(cont’d.)
• Problems with cellulosic ethanol
– Chemical processes still being developed
– Growing enough switchgrass would require
too much land
• Evaluating use of algae and bacteria
© Cengage Learning 2015
Trade-Offs
Liquid Biofuels
Advantages
Disadvantages
Reduced CO2
emissions for
some crops
Fuel crops can
compete with food
crops for land and
raise food prices
Medium net
energy yield for
biodiesel from oil
palms
Fuel crops can be
invasive species
Medium net
energy yield for
ethanol from
sugarcane
Low net energy yield
for corn ethanol and
for biodiesel from
soybeans
Higher CO2
emissions from
corn ethanol
Fig. 16-28, p. 426
16-7 What Are the Advantages and
Disadvantages of Geothermal Energy?
• Geothermal energy has great potential for
supplying many areas with heat and
electricity, and has a generally low
environmental impact
– However, the sites where it can be produced
economically are limited
© Cengage Learning 2015
We Can Get Energy by Tapping the Earth’s
Internal Heat
• With geothermal energy, heat is stored in:
– Soil
– Underground rocks
– Fluids in the earth’s mantle
• Geothermal heat pump system
– Energy efficient and reliable
– Environmentally clean
– Cost effective to heat or cool a space
© Cengage Learning 2015
We Can Get Energy by Tapping the Earth’s
Internal Heat (cont’d.)
• Hydrothermal reservoirs
– Drill wells and extract various steams, water
– U.S. is the world’s largest producer
• Geothermal energy problems
– High cost of tapping hydrothermal reservoirs
– Dry- or wet-steam geothermal reservoirs
could be depleted
– Could create earthquakes
© Cengage Learning 2015
2. Heat from underground spins
a turbine to power a generator
and produce electricity
Generator
Steam turbine
Heat
exchanger
3. Steam from turbine condenses
to water and is pumped back
down to geothermal reservoir
Production well
Injection well
1. Hot water or steam is pumped
under pressure to the surface
from underground
Geothermal
reservoir
© Cengage Learning 2015
Fig. 16-30a, p. 428
© Cengage Learning 2015
Fig. 16-30b, p. 428
Trade-Offs
Geothermal Energy
Advantages
Disadvantages
Medium net energy
yield and high
efficiency at
accessible sites
High cost except at
concentrated and
accessible sites
Lower CO2
emissions than
fossil fuels
Scarcity of suitable
sites
Low cost at
favorable sites
Noise and some
CO2 emissions
Fig. 16-31, p. 430
16-8 The Advantages and Disadvantages
of Using Hydrogen as an Energy Source
• Hydrogen is a clean energy source as long
as it is not produced with the use of fossil
fuels
– However, it has a negative net energy yield
© Cengage Learning 2015
Will Hydrogen Save Us?
• Hydrogen as a fuel
– Eliminates most of the air pollution problems
– Reduces threats of global warming
© Cengage Learning 2015
Will Hydrogen Save Us?
• Some challenges
– Chemically locked in water and organic
compounds – net negative energy yield
– Expensive fuel cells are the best way to use
hydrogen
– CO2 levels dependent on method of hydrogen
production
© Cengage Learning 2015
Electrons
Hydrogen
gas (H2) in
Anode
Polymer
electrolyte
membrane
Cathode
Water vapor
(H2O) out
Protons
Air (O2) in
Fig. 16-32, p. 430
Will Hydrogen Save Us? (cont’d.)
• Production and storage of H2
– Must be produced using other sources of
energy
• Hydrogen-powered vehicles – prototypes
available
• Can we produce hydrogen on demand?
• Larger fuel cells – fuel-cell stacks
© Cengage Learning 2015
Trade-Offs
Hydrogen
Advantages
Disadvantages
Can be produced
Fuel
from plentiful
cell
water at some sites
Negative net
energy yield
No CO2 emissions
if produced with
use of renewables
CO2 emissions
if produced from
carbon-containing
compounds
Good substitute
for oil
High costs create
need for subsidies
High efficiency in
fuel cells
Needs H2 storage
and distribution
system
Fig. 16-33, p. 432
16-9 How Can We Make the Transition to
a More Sustainable Energy Future?
• We can make the transition to a more
sustainable energy future by:
– Greatly improving energy efficiency
– Using a mix of renewable energy resources
– Including the environmental and health costs
of energy resources in their market prices
© Cengage Learning 2015
Choosing Energy Paths
• General conclusions:
– Gradual shift to smaller, decentralized
micropower systems
– Combination of increased energy efficiency
and regulated use of natural gas will be the
best way to transition to renewable energy
– Because fossil fuels are cheap we will
continue to use them
© Cengage Learning 2015
Bioenergy power plants
Wind farm
Small solar-cell
power plants
Fuel cells
Solar-cell
rooftop
systems
Rooftop solarcell arrays
Smart electrical
and distribution
system
Commercial
Residential
Small
wind
turbine
Industrial
© Cengage Learning 2015
Microturbines
Stepped Art
Fig. 16-34, p. 433
Economics, Politics, Education, and
Sustainable Energy Resources
• Government strategies:
– Keep the prices of selected energy resources
artificially low to encourage their use
– Keep energy prices artificially high for
selected resources to discourage their use
– Consumer education
© Cengage Learning 2015
© Cengage Learning 2015
Fig. 16-35, p. 434
Three Big Ideas
• We should evaluate energy resources on
the basis of:
– Their potential supplies
– Their net energy yields
– Environmental and health impacts of using
them
© Cengage Learning 2015
Three Big Ideas (cont’d.)
• By using a mix of renewable energy
sources we could drastically reduce
pollution, greenhouse gas emissions, and
biodiversity losses
– Solar, wind, flowing water, sustainable
biofuels, and geothermal energy
© Cengage Learning 2015
Three Big Ideas (cont’d.)
• Making the transition to a more
sustainable energy future will require:
– Sharply increasing energy efficiency
– Using a mix of environmentally friendly
renewable energy resources
– Including the harmful environmental and
health costs of energy resources in their
market prices
© Cengage Learning 2015
Tying It All Together: Wind Power and
Sustainability
• Relying on a diversity of direct and indirect
forms of solar energy:
– Would implement three principles of
sustainability
– Recycle and reuse materials to reduce
consumption of energy
– Mimic nature’s reliance on biodiversity by
diversifying energy sources
© Cengage Learning 2015