Energy
Chapter 13
Section 13-1
WHAT IS NET ENERGY AND
WHY IS IT IMPORTANT?
Basic science: Net energy is the
only energy that really counts
• The usable amount of high-quality energy
available from a given quantity of an energy
resource is its net energy yield: the total
amount of useful energy available from an
energy resource minus the energy needed to
make it available to consumers.
• We can express net energy as the ratio of
energy produced to the energy used to
produce it. As the ratio increases, the net energy
also rises. When the ratio is less than 1, there
is a net energy loss.
Net energy ratios for various energy systems
over their estimated lifetimes differ widely
Fig. 13-2a, p. 301
Fig. 13-2b, p. 301
Fig. 13-2c, p. 301
Fig. 13-2d, p. 301
Energy resources with low or negative net
energy need help to compete in the marketplace
• Any energy resource with a low or negative net
energy ratio cannot compete in the open
marketplace with other energy alternatives with
higher net energy ratios unless it receives
financial support from the government
(taxpayers) or other outside sources of funding.
– For example, the low net energy yield for the nuclear
power fuel cycle is one reason why many
governments throughout the world must heavily
support nuclear power financially to make it available
to consumers at an affordable price.
Section 13-2
WHAT ARE THE ADVANTAGES
AND DISADVANTAGES OF
FOSSIL FUELS?
Fossil fuels supply most of our
commercial energy
• The direct input of solar energy produces
several other forms of renewable energy
resources: wind, flowing water, and biomass.
• Most commercial energy comes from extracting
and burning nonrenewable energy resources
obtained from the earth’s crust.
– 87% from carbon-containing fossil fuels (oil, natural
gas, and coal).
– 6% from nuclear power.
– 8% from renewable energy resources—biomass,
hydropower, geothermal, wind, and solar energy.
Energy use by source throughout
the world and US in 2009
When crude oil is refined, many of its
components are removed at various levels
How long might supplies of
conventional crude oil last?
• Crude oil is now the single largest source of
commercial energy in the world.
• Proven oil reserves are identified deposits from
which conventional crude oil can be extracted
profitably at current prices with current
technology.
• Geologists project that known and projected
global reserves of conventional crude oil will
be 80% depleted sometime between 2050 and
2100. The remaining 20% will likely be too
costly to remove.
How long might supplies of
conventional crude oil last?
• Options include:
– look for more oil.
– use less oil.
– waste less oil.
– use other energy resources.
OPEC controls most of the
world’s crude oil supplies
• 13 countries make up the Organization of
Petroleum Exporting Countries (OPEC).
– In 2010, OPEC holds about 77% of the world’s
proven crude oil reserves.
– OPEC’s members are Algeria, Angola, Ecuador,
Indonesia, Iran, Iraq, Kuwait, Libya, Nigeria, Qatar,
Saudi Arabia, the United Arab Emirates, and
Venezuela.
• The U.S. has only about 2% of the world’s
proven oil reserves. China has only 1.1%, India
has 0.4%, and Japan has no oil reserves.
OPEC controls most of the
world’s crude oil supplies
• Currently, the world’s largest producers of oil
are, in order, Russia, Saudi Arabia, and the
U.S. Energy experts project that by about 2020,
Iraq will become the world’s third largest oil
producer.
• Since 1984, production of conventional crude oil
from proven reserves has exceeded new oil
discoveries. Since 2005, global crude oil
production has generally leveled off. Of the
world’s 64 major oil fields, 54 are now in
decline.
Crude oil use has advantages
and disadvantages
Using crude oil has advantages
and disadvantages
• Oil spills cause catastrophic damage.
– In 2010, the BP Company’s Deepwater Horizon oildrilling rig exploded, spilling an estimated 679
million liters (180million gallons) of crude oil into U.S.
Gulf Coast waters.
– In 1989, the oil tanker Exxon Valdez ran aground
and spilled 42 million liters (11 million gallons) of oil
into Alaskan waters.
– More than 2.5 times the estimated amount of crude oil
spilled in the 2010 Gulf Coast disaster has been
spilled from off the coast of Nigeria with little media
attention.
Will heavy oil be a useful
resource?
• Oil shale is rock that contains a solid combustible
mixture of hydrocarbons called kerogen which can be
processed to produce shale oil.
• Producing shale oil requires large amounts of water and
has a low net energy and a very high environmental
impact.
• Estimated potential global supplies of unconventional shale
oil are about 240 times larger than estimated global
supplies of conventional crude oil.
• Shale has a low net energy yield so would require
subsidies to compete on the open market, and shale
extraction would have a high environmental impact, causing
severe land disruption, high water use, and high CO2
Shale oil can be extracted from
oil shale rock
Using heavy oil from oil shale and tar sands as
energy source has advantages and disadvantages
Natural gas is a useful and
clean-burning fossil fuel
• Natural gas is a mixture of gases of which
50–90% is methane (CH4).
– Has high net energy.
– Versatile fuel that can be burned to heat indoor
space and water, propel vehicles and produce
electricity.
– Lies above most reservoirs of crude oil.
– When a natural gas field is tapped, propane and
butane gases are liquefied and removed as liquefied
petroleum gas (LPG).
– Cleanest-burning among the fossil fuels, releasing
much less CO2 per unit of energy than coal, crude oil,
and synthetic crude oil from tar sands and oil shale.
Using conventional natural gas has
advantages and disadvantages
Use of fracking to extract
natural gas is controversial
• Hydraulic fracturing, or fracking, pumps
water mixed with sand and some toxic
chemicals underground to fracture deep rock
and free up natural gas stored there.
– The gas flows out, along with a toxic slurry of
water, salts, toxic heavy metals, and naturally
occurring radioactive materials that is stored in
tanks and holding ponds.
– Drillers maintain that fracking is necessary for
exploiting this reserve at a reasonably low cost,
and they argue that no groundwater contamination
directly due to fracking has ever been recorded.
Coal is a plentiful but dirty fuel
• Coal is a solid fossil fuel formed from the
remains of land plants that were buried 300–
400 million years ago and exposed to intense
heat and pressure over those millions of years.
• Coal is burned in power plants to generate about
42% of the world’s electricity, and burned in
industrial plants to make steel, cement, and
other products.
• The three largest coal-burning countries are
China, the U.S., and India.
• Coal is plentiful and cheap.
Different types of coal have
formed over millions of years
Increasing heat and carbon content
Increasing moisture content
Peat
Lignite
(not a coal)
(brown coal)
Heat
Heat
Heat
Pressure
Pressure
Pressure
Partially decayed plant
matter in swamps and
bogs; low heat content
Bituminous
(soft coal)
Low heat content; low
sulfur content; limited
supplies in most areas
Extensively used as a
fuel because of its high
heat content and large
supplies; normally has
a high sulfur content
Anthracite
(hard coal)
Highly desirable fuel
because of its high heat
content and low sulfur
content; supplies are
limited in most areas
Fig. 13-12, p. 310
Coal is a plentiful but dirty fuel
• Mining and burning coal have severe impacts
on the earth’s air, water, land, climate, and
human health.
– Coal-burning power and industrial plants are among
the largest emitters of the greenhouse gas, CO2.
– Coal burning emits trace amounts of toxic and
radioactive materials.
– Burning coal produces a highly toxic ash that must
be safely stored, essentially forever.
– China uses three times as much coal as the U.S.
and it has become the world’s leading emitter of CO2
and of sulfur dioxide.
This power plant burns pulverized coal to boil
water and produce steam that spins a turbine to
produce electricity.
Waste heat
Coal bunker
Cooling
tower
transfers
waste heat to
atmosphere
Turbine
Generator
Cooling
loop
Stack
Pulverizing
mill Boiler
Condenser
Filter
Toxic ash disposal
Fig. 13-13, p. 310
CO2 emissions vary with
different energy resources
Coal-fired
electricity
286%
Synthetic oil and
gas produced
from coal
150%
Coal
100%
Tar sand
92%
Oil
86%
Natural gas
Nuclear power
fuel cycle
Geothermal
58%
17%
10%
Stepped Art
Fig. 13-15, p. 311
Coal has advantages and
disadvantages
Section 13-3
WHAT ARE THE ADVANTAGES
AND DISADVANTAGES OF
NUCLEAR ENERGY?
How does a nuclear fission
reactor work?
• Nuclear power plant is a highly complex and costly
system designed to perform a relatively simple
task: to boil water to produce steam that spins
a turbine and generates electricity.
• A controlled nuclear fission reaction is used to
provide the heat.
– The fission reaction takes place in a reactor.
– Light-water reactors (LWRs) produce 85% of the world’s
nuclear-generated electricity (100% in the U.S.).
– The fuel for a reactor is made from uranium ore mined
from the earth’s crust, then enriched and processed into
pellets of uranium dioxide.
A water-cooled nuclear power
plant
Fig. 13-17a, p. 314
Bioenergy power plants
Wind farms
Small solar-cell
power plants
Fuel
cells
Solar-cell
rooftop
systems
Rooftop solarcell arrays
Smart electrical
distribution
system
Commercial
Small
Residential wind
turbine
Industrial
Microturbines
Fig. 13-47, p. 342
Small amounts of
radioactive gases
Uranium fuel
input (reactor
core)
Control rods
Containment shell
Waste heat
Heat exchanger
Steam Turbine
Generator
Hot
coolant
Hot
water
output
Coolant
Cool
water
input
Moderator
Shielding
Pressure Coolant
vessel
passage
Periodic removal and
storage of
radioactive wastes
and spent
fuel assemblies
Periodic
removal and
storage
of radioactive
liquid wastes
Water
Useful
electrical
energy
about 25%
Waste heat
Condenser
Water source
(river, lake, ocean)
Fig. 13-17a, p. 314
What is the nuclear fuel cycle?
– In addition to a nuclear power plant, the
nuclear fuel cycle includes:
•
•
•
•
mining uranium.
processing and enriching the uranium to make fuel.
using it in the reactor.
safely storing the resulting highly radioactive
wastes for thousands of years until their
radioactivity falls to safe levels.
• retiring the highly radioactive plant by taking it
apart.
• storing its high- and moderate-level radioactive
material safely for thousands of years.
Nuclear power cycle to produce energy
has advantages and disadvantages
Can nuclear power lessen dependence on imported
oil and help reduce projected global warming?
• Nuclear power advocates contend it will:
– Reduce oil dependency.
– Reduce or eliminate CO2 emissions and reduce the
threat of projected climate change.
• Dissenters claim that
– While nuclear power plants do not produce
greenhouse gasses, the nuclear fuel cycle does.
– Increased use of nuclear power in the U.S. will make
the country dependent on imports of uranium.
– While nuclear emissions are much lower than those
from coal-burning power plants, they still contribute to
projected atmospheric warming and climate change.
Nuclear Power Is Not
Expanding Very Rapidly
• 1950s prediction was that by the year 2000
at least 1,800 nuclear power plants would
supply most of the world’s electricity.
• Some 441 commercial nuclear reactors
in 31 countries produce only 6% of the
world’s commercial energy and 14% of
its electricity.
• Nuclear power is now the world’s
slowest-growing form of commercial
energy.
Experts Disagree about the
Future of Nuclear Power
• Opposition to Nuclear Power.
– Nuclear power industry could not exist
without support from governments and
taxpayers.
– In the U.S., the government provides huge
subsidies, tax breaks, and loan guarantees
to the nuclear industry, and accident
insurance guarantees, because insurance
companies have refused to fully insure any
nuclear reactor.
– Public concerns about the safety of nuclear
reactors.
Some critics of nuclear power say any new
generation of nuclear power plants should
beat all of these criteria; so far, none do
Support for Nuclear Power
• Develop nuclear fusion
– A nuclear change at the atomic level in which the
nuclei of two isotopes of a light element such as
hydrogen are forced together at extremely high
temperatures until they fuse to form a heavier
nucleus, releasing energy in the process
– No risk of a meltdown or of a release of large
amounts of radioactive materials, and little risk of
the additional spread of nuclear weapons. In addition
to generating electricity, fusion power could be used to
destroy hazardous wastes, and it could have many
other uses.
Section 13-4
WHY IS ENERGY EFFICIENCY
AN IMPORTANT ENERGY
RESOURCE?
We waste huge amounts of
energy
• Energy efficiency is the measure of how much
work we can get from each unit of energy we use.
• Roughly 84% of all commercial energy used in
the U.S. is wasted.
– About 41% of this energy is unavoidably lost
because of the degradation of energy quality imposed
by the second law of thermodynamics.
– The other 43% is wasted unnecessarily, mostly due
to the inefficiency of incandescent light bulbs,
industrial motors, most motor vehicles, coal and nuclear
power plants, and numerous other energy-consuming
devices.
– Poor insulation and building design also contribute.
Benefits of reducing energy
waste
A comparison of the changes in
fuel economy standards
More energy efficient vehicles
are on the way
• Energy-efficient, gasoline-electric hybrid car.
– A small gasoline-powered motor and an electric
motor used to provide the energy needed for
acceleration and hill climbing.
– The most efficient models of these cars, such as the
2011 Toyota Prius, get a combined city/highway
mileage of up to 22 kpl (51 mpg) and emit about 65%
less CO2 per kilometer driven than a comparable
conventional car emits.
– A newer option is the plug-in hybrid electric
vehicle—a hybrid with a second and more powerful
battery that can be plugged into an electrical outlet
and recharged.
Hybrid vehicles
More energy efficient vehicles
are on the way
• The next superefficient car may be an electric
vehicle that uses a fuel cell—a device that
uses hydrogen gas (H2) as a fuel to produce
electricity. Fuel cells are at least twice as
efficient as internal combustion engines, have
no moving parts, and require little maintenance.
• Fuel efficiency for all types of cars could nearly
double if car bodies were made of ultralight and
ultrastrong composite materials.
More energy efficient vehicles
are on the way
• Other ways to save energy in transportation
include
– shifting from diesel-powered to electrified rail
systems
– building accessible mass transit systems within
cities
– constructing high-speed rail lines between cities
– encourage bicycle use by designating bike lanes on
highways and city streets
– using video conferencing as an alternative to flying
employees to meetings.
Thermogram showing heat
losses
We can save energy and money
in existing buildings
• Have an expert make an energy audit of a
house or other building to suggest ways to
improve energy efficiency.
– Insulate the building and plug leaks.
– Use energy-efficient windows.
– Heat houses more efficiently.
– Heat water more efficiently.
– Use energy-efficient appliances.
– Use energy-efficient lighting.
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. 13-29, p. 328
Section 13-5
WHAT ARE THE ADVANTAGES
AND DISADVANTAGES OF
USING RENEWABLE ENERGY
RESOURCES?
We can use renewable energy
for many purposes
• Renewable solar energy comes directly
from the sun or indirectly from wind,
moving water, and biomass.
• Renewable energy can come from
geothermal energy from the earth’s
interior.
• Renewable energy could provide 20%
of the world’s electricity by 2025 and
50% by 2050.
We can heat buildings and
water with solar energy
• Passive solar heating system absorbs
and stores heat from the sun directly.
• Active solar heating system uses energy
from the sun by pumping a heatabsorbing fluid through special
collectors usually mounted on a roof or
on special racks to face the sun.
Homes can be heated with
passive or active solar systems
Summer
sun
White or light-colored
roofs reduce overheating
Vent allows
hot air to
escape in
summer
Heavy
insulation
Winter
sun
Superwindow
Superwindow
Stone floor and wall for heat storage
PASSIVE
Fig. 13-30a, p. 329
Solar collector
White or light-colored
roofs reduce overheating
Heat to house
(radiators or
forced air duct)
Pump
Heavy
insulation
Hot
water
tank
Superwindow
Heat
exchanger
ACTIVE
Fig. 13-30b, p. 329
Heating a house with passive or active solar energy
systems has advantages and disadvantages
Solar thermal power
Using solar energy to generate high-temperature heat
and electricity has advantages and disadvantages
Using solar cells has
advantages and disadvantages
Large-scale hydropower has
advantages and disadvantages
Wind power has advantages
and disadvantages
Solid biomass has advantages
and disadvantages
Advantages and disadvantages
of liquid biofuels
We can get energy by tapping
the earth’s internal heat
• Geothermal energy is heat stored in soil,
underground rocks, and fluids in the earth’s
mantle.
• A geothermal heat pump system can heat and
cool a house by exploiting the temperature
differences between the earth’s surface and
underground almost anywhere in the world at a
depth of 3–6 meters (10–20 feet).
– Most energy-efficient, reliable, environmentally
clean, and cost-effective way to heat or cool a
space. It produces no air pollutants and emits no
CO2.
We can get energy by tapping
the earth’s internal heat
• Drill wells into hydrothermal reservoirs of
geothermal energy to extract steam or
hot water, which is used to heat homes
and buildings, provide hot water, grow
vegetables in greenhouses, raise fish in
aquaculture ponds, and spin turbines to
produce electricity.
– The U.S. is the world’s largest producer of
geothermal electricity from hydrothermal
reservoirs.
A geothermal heat pump system can
heat or cool a house almost anywhere
Using geothermal energy has
advantages and disadvantages
Section 13-6
HOW CAN WE MAKE THE
TRANSITION TO A MORE
SUSTAINABLE ENERGY
FUTURE?
Choosing energy paths
• Three general conclusions of experts
who have evaluated energy alternatives:
– There will likely be a gradual shift:
• from large, centralized power systems such as
coal and nuclear power plants to smaller,
decentralized power systems such as household
and neighborhood solar-cell panels, rooftop solar
water heaters, and small natural gas turbines.
• from gasoline-powered motor vehicles to hybrid
and plug-in electric cars.
• to fuel cells for cars and to stationary fuel cells
for houses and commercial buildings.
Decentralized power system
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
Microturbines
Stepped Art
Fig. 13-47, p. 342
Suggestions for transitioning to
a more sustainable future
Economics, politics, and education can help
us shift to more sustainable energy resources
• Governments can use three strategies to
help stimulate or reduce the short-term
and long-term use of a particular energy
resource.
– Keep the prices of selected energy
resources artificially low to encourage their
use.
– Keep the prices of selected energy
resources artificially high to discourage
their use.
– Governments can emphasize consumer
education.
Three big ideas
• We should evaluate energy resources on the basis of
their potential supplies, how much net energy they
provide, and the environmental impacts of using them.
• Using a mix of renewable energy sources—
especially solar, wind, flowing water, sustainable
biofuels, and geothermal energy—can drastically
reduce pollution, greenhouse gas emissions, and
biodiversity losses.
• Making the transition to a more sustainable energy
future will require sharply reducing energy waste,
using a mix of environmentally friendly renewable
energy resources, and including the harmful
environmental costs of energy resources in their market
prices.
End of “Short Version”
• The slides that follow are those taken out
of the “long version” of this same lecture.
You should still read the following slides
for better understanding, but I will not go
over them in class unless you have
specific questions.
We depend heavily on oil
• Crude oil (petroleum), is a black, gooey liquid
consisting of hundreds of different combustible
hydrocarbons along with small amounts of sulfur,
oxygen, and nitrogen impurities.
– Also known as conventional oil and as light or sweet
crude oil.
– Oil, coal, and natural gas are called fossil fuels
because they were formed from the decaying remains
(fossils) of organisms that lived millions of years ago.
• When the rate of crude oil production starts
declining it is referred to as peak production for
the well.
We depend heavily on oil
• Global peak production is the point in time
when we reach the maximum overall rate of
crude oil production for the whole world.
• After extraction, crude oil is transported to a
refinery by pipeline, truck, or ship (oil
tanker).
• Crude oil is heated to different boiling
points in a complex process called refining
to separate it into different layers, such as
petrochemicals.
OPEC controls most of the
world’s crude oil supplies
• According to some analysts, in order to
keep using conventional oil at the
projected increasing rate of consumption,
we must discover proven reserves of
conventional oil equivalent to the current
Saudi Arabian supply every 5 years. Most
oil geologists say this is highly unlikely.
Using crude oil has advantages
and disadvantages
• Extraction, processing, and burning of
nonrenewable oil and other fossil fuels
have severe environmental impacts.
– Land disruption.
– Air pollution.
– Greenhouse gas emissions.
– Water pollution.
– Loss of biodiversity.
Use of fracking to extract
natural gas is controversial
– Scientists and citizens point out that there is no
guarantee that sharply increasing use of the process
will not contaminate groundwater or that holding
ponds and tanks used to store the toxic slurry will not
leak and pollute rivers and streams.
– People who rely on aquifers and streams in these
areas for their drinking water have little protection
from pollution of their water supplies that might result
from natural gas drilling.
Use of fracking to extract
natural gas is controversial
• Natural gas can be transported as liquefied
natural gas (LNG). However, LNG has a low net
energy yield, as more than a third of its energy
content is used to process it and to deliver it to
users.
• The long-term global outlook for conventional
natural gas supplies is better than for crude oil.
• Potential sources of unconventional natural gas
include coal bed methane gas and methane
hydrate, but environmental impacts and cost may
limit their use.
Use of fracking to extract
natural gas is controversial
– Scientists and citizens point out that there is no
guarantee that sharply increasing use of the process
will not contaminate groundwater or that holding
ponds and tanks used to store the toxic slurry will not
leak and pollute rivers and streams.
– People who rely on aquifers and streams in these
areas for their drinking water have little protection
from pollution of their water supplies that might result
from natural gas drilling.
Use of fracking to extract
natural gas is controversial
• Natural gas can be transported as liquefied
natural gas (LNG). However, LNG has a low net
energy yield, as more than a third of its energy
content is used to process it and to deliver it to
users.
• The long-term global outlook for conventional
natural gas supplies is better than for crude oil.
• Potential sources of unconventional natural gas
include coal bed methane gas and methane
hydrate, but environmental impacts and cost may
limit their use.
Coal is a plentiful but dirty fuel
– Coal is cheap but most of the harmful
environmental and health costs are not
included in the price.
– The clean coal campaign.
• Powerful U.S. coal companies and utilities oppose
measures.
• Publicity campaign built around the misleading
notion of clean coal.
– Burn coal more cleanly by adding costly air pollution
control devices.
– There is no such thing as clean coal.
How does a nuclear fission
reactor work?
• Pellets are packed into fuel rods which are then
grouped into fuel assemblies and placed in the
core of a reactor.
• Control rods are moved in and out of the reactor
core to regulate the amount of power produced.
• A coolant, usually water, circulates through the
reactor’s core to remove heat, which keeps fuel
rods and other materials from melting and
releasing massive amounts of radioactivity into the
environment.
How does a nuclear fission
reactor work?
• A containment shell surrounds the reactor core to
keep radioactive materials from escaping into the
environment in case there is an internal explosion
or a melting of the reactor’s core.
• Light water reactors are highly inefficient; the net
energy loss is about 82%, without taking into
account the energy needed to dismantle a plant at
the end of its life and transport and store its
radioactive materials for thousands of years.
What is the nuclear fuel cycle?
• A nuclear power plant is only one part of the
nuclear fuel cycle, which also includes the
mining of uranium, processing and enriching the
uranium to make fuel, using it in the reactor,
safely storing the resulting highly radioactive
wastes for thousands of years until their
radioactivity falls to safe levels, and retiring the
highly radioactive plant by taking it apart and
storing its high- and moderate-level radioactive
material safely for thousands of years.
Storing spent radioactive fuel
rods presents risks
• High-level radioactive wastes consist
mainly of spent fuel rods and assemblies.
• After 3–4 years in a reactor, spent fuel
rods are removed and stored in a deep
pool of water contained in a steel-lined
concrete basin for cooling.
• After about 5 years of cooling, the fuel
rods can be stored upright on concrete
pads in sealed dry-storage casks made of
heat-resistant metal alloys and concrete.
Storing spent radioactive fuel
rods presents risks
• Stored spent radioactive fuel rods are
vulnerable to terrorist acts.
• Storage pools and dry casks at 68 nuclear
power plants in 31 U.S. states are
especially vulnerable to sabotage or
terrorist attack.
• Critics call for construction of much more
secure structures to protect spent-fuel
storage pools and dry casks.
Dealing with high-level radioactive wastes
produced by nuclear power is a difficult problem
• High-level radioactive wastes consist mainly of
spent fuel rods and assemblies from commercial
nuclear power plants and dismantled plants, and
assorted wastes from the production of nuclear
weapons.
• Spent fuel rods can be processed to remove
radioactive plutonium, as is done with some of
the other radioactive wastes we produce.
• Reduces the storage time from up to 240,000 to
about 10,000 years.
Dealing with high-level radioactive wastes
produced by nuclear power is a difficult problem
• Deep burial in a geologically acceptable
underground repository is the safest and
cheapest way to store these and other
high-level radioactive wastes.
• All worn-out nuclear plant plants will have
to be dismantled and their high-level
radioactive materials will have to be stored
safely for thousands of years.
Support for Nuclear Power
• Governments should continue funding research,
development, and pilot-plant testing of potentially
safer and cheaper second-generation reactors.
• New advanced light-water reactors (ALWRs) have
built-in safety features designed to make
explosions and releases of radioactive emissions
almost impossible.
• Replace today’s uranium-based reactors with new
ones based on the element thorium which are
less costly and safer, and would cut the amount of
nuclear waste generated in half.
We waste huge amounts of
energy
• Reducing energy waste is the most efficient way to
provide more energy, reduce pollution and
environmental degradation, and slow climate
change.
– Widely used devices that waste large amounts of
energy unnecessarily:
• Incandescent light bulbs: use only about 5% to produce light.
The other 95% is wasted as heat.
• The internal combustion engine, which propels most motor
vehicles and wastes about 80% of the energy in its fuel.
• A nuclear power plant, wastes about 65% of the energy in its
nuclear fuel.
• A coal-fired power plant wastes about 66% of its energy.
We can save energy and money
in industry
• Industry accounts for about 30% of the world’s
energy consumption, 33% in U.S., mostly for the
production of metals, chemicals, petrochemicals,
cement, and paper.
• Ways for industries to cut energy waste:
– Cogeneration, combines two useful forms of energy (e.g.
steam and electricity), produced from the same fuel.
– Save energy and money in industry by replacing energywasting electric motors.
– Recycling materials, such as steel and other metals, is a
third way for industry to save energy and money.
– Switch incandescent lighting to higher-efficiency lighting.
We can save energy and money
in transportation
• As a result of the 1973–1974 oil embargo imposed by
OPEC, the U.S. government imposed higher fuel
efficiency standards for new vehicles sold in the U.S.
beginning in 1978.
• Between 1973 and 1985, average fuel efficiency for new
vehicles sold in the U.S. rose sharply because of the
corporate average fuel economy (CAFE) standards.
• Greatly increased sales of light trucks and SUVs lead to
a decline in fuel efficiency in the U.S. between 1985 and
2005.
• Fuel economy standards for new vehicles in Europe,
Japan, China, and Canada are much higher than are
those in the U.S.
We can save energy and money
in transportation
• In 2007, the U.S. Congress passed a law requiring new
motor vehicles to have an average combined fuel
efficiency of 15 kilometers per liter (35 miles per gallon)
by 2020.
• One way to include more of the real cost of gasoline in
its market price is through gasoline taxes.
• Government could encourage consumers them to buy
more fuel-efficient vehicles with a fee-bate program in
which buyers of inefficient vehicles would pay a high fee,
and the resulting revenues would be given to buyers of
fuel-efficient vehicles as rebates.
We can design buildings that
save energy and money
• Changes in building design and construction
could save 30–40% of the energy used globally.
• Orienting a building so it can get more of its heat
from the sun can save up to 20% of heating
costs and as much as 75% when the building is
well insulated and airtight.
• Green architecture, based on energy-efficient
and money-saving designs, makes use of
natural lighting, solar heating and cells, recycled
wastewater, and energy-efficient appliances and
lighting.
We can design buildings that
save energy and money
• Super insulated houses in Sweden use 90% less
energy for heating and cooling than typical
American homes of the same size.
• Green building certification standards now exist
in 21 countries, thanks to the efforts of the World
Green Building Council.
• The U.S. Green Building Council’s Leadership in
Energy and Environmental Design (LEED)
program awards certificates to buildings that
meet certain efficiency standards.
Why are we still wasting so
much energy and money?
• Common energy resources are artificially cheap, mainly
due to government subsidies and prices do not include
the harmful environmental and health costs.
• There are few large and long-lasting government tax
breaks, rebates, low-interest and long-term loans, and
other economic incentives for consumers and
businesses to invest in improving energy efficiency.
• The U.S. government has done a poor job of
encouraging fuel efficiency in motor vehicles and
educating the public about the environmental and
economic advantages of cutting energy waste.
• Inadequate energy-efficiency building codes and
appliance standards.
Why are we still wasting so
much energy and money?
• Common energy resources are artificially cheap, mainly
due to government subsidies and prices do not include
the harmful environmental and health costs.
• There are few large and long-lasting government tax
breaks, rebates, low-interest and long-term loans, and
other economic incentives for consumers and
businesses to invest in improving energy efficiency.
• The U.S. government has done a poor job of
encouraging fuel efficiency in motor vehicles and
educating the public about the environmental and
economic advantages of cutting energy waste.
• Inadequate energy-efficiency building codes and
appliance standards.
We can use renewable energy
for many purposes
• Why renewable energy provides only 13% of the
world’s energy and 8% in the U.S.:
– Since 1950, government tax breaks, subsidies, and
funding for research and development of renewable
energy resources have been much lower than those for
fossil fuels and nuclear power.
– Although subsidies and tax breaks for fossil fuels and
nuclear power have essentially been guaranteed for
many decades, those for renewable energy in the U.S.
have to be renewed by Congress every few years.
– Nonrenewable fossil fuels and nuclear power are
artificially cheap.
We can cool buildings naturally
• Open windows to take advantage of breezes and
use fans to keep the air moving.
• A living roof can make a huge difference in keeping
a building cool.
• Install superinsulation and high-efficiency windows.
• Block the high summer sun with window overhangs
or awnings.
• Use a light-colored roof to reflect as much as 80%
of the sun’s heat.
• Use geothermal heat pumps for heating and
cooling.
We can concentrate sunlight to produce
high-temperature heat and electricity
• Solar thermal systems use different methods to
collect and concentrate solar energy in order to
boil water and produce steam for generating
electricity
• The net energy yield for solar thermal systems is
only about 3%, which means that they need large
government subsidies or tax breaks in order to
compete in the marketplace with alternatives that
have higher net energy yields.
• Inexpensive solar cookers focus and concentrate
sunlight for cooking food and sterilizing water.
We can use sunlight directly to
produce electricity
• Solar energy can be converted directly into electrical
energy by photovoltaic cells, commonly called solar cells.
• Solar cells have no moving parts, are safe and quiet, and
produce no pollution or greenhouse gases during
operation.
• The material used in solar cells can be made into paperthin rigid or flexible sheets that can be incorporated into
roofing materials and attached to a variety of surfaces
such as walls, windows, and clothing.
• Generating electricity with solar cells could become nearly
as efficient as using coal-burning power plants without
producing the air pollutants and climate-changing CO2
emitted by those plants.
We can produce electricity from
falling and flowing water
• Hydropower uses the kinetic energy of flowing and
falling water to produce electricity.
• Indirect form of solar energy because it is based on
the evaporation of water, which is part of the earth’s
solar-powered water cycle.
• Most common approach to harnessing hydropower
is to build a high dam across a large river to create a
reservoir.
• Hydropower is the world’s leading renewable energy
source for the production of electricity. In order, the
world’s top six producers of hydropower are China,
Canada, Brazil, the U.S., Russia, and Norway.
We can produce electricity from
falling and flowing water
• Some analysts expect that use of large-scale
hydropower plants will fall slowly over the next several
decades as many existing reservoirs fill with silt and
become useless faster than new systems are built.
• Microhydropower generators are small floating
turbines that use the power of flowing water to turn
rotor blades, which spin a turbine to produce electric
current. They provide electricity at a low cost with a
very low environmental impact.
• Ocean tides and waves contain energy. Dams have
been built across the mouths of some bays and
estuaries to capture the energy in ocean water
movement.
Using wind to produce electricity is an
important step toward sustainability
• Wind turbines have been erected in large
numbers at favorable sites to create wind farms
• Since 1990, wind power has been the world’s
second fastest-growing source of energy after
solar cells.
• Wind turbines can be interconnected in arrays of
tens to hundreds. These wind farms or wind
parks can be located on land or offshore.
• In 2009, a Harvard University study estimated
that wind power has the potential to produce 40
times the world’s current use of electricity.
Using wind to produce electricity is an
important step toward sustainability
• Benefits:
– Wind is widely distributed and inexhaustible
– Wind power is mostly carbon-free and
pollution-free.
– A wind farm can be built within 9 to 12
months and expanded as needed.
– Homeowners can also use small and quiet
wind turbines to produce their own electricity.
– Wind power has a moderate-to-high net
energy ratio.
Using wind to produce electricity is an
important step toward sustainability
• Areas with the greatest wind power potential are
often far from cities so may require controversial
upgrading and expansion of electrical grid systems.
• Winds can die down and thus require a backup
source of power, such as natural gas, for generating
electricity.
• Some people in populated areas oppose wind farms
as being unsightly and noisy.
• In windy parts of the U.S. Midwest and in Canada,
farmers and ranchers are paid royalties for each
wind turbine located their land and can still grow
crops or graze cattle.
We can produce energy by
burning solid biomass
• Biomass consists of plant materials (such
as wood and agricultural waste) and
animal wastes that can be burned directly
as a solid fuel or converted into gaseous
or liquid biofuels.
• Solid biomass is burned mostly for heating
and cooking, but also for industrial
processes and for generating electricity.
We can produce energy by
burning solid biomass
– Wood, wood wastes, charcoal (made from wood),
animal manure.
– In agricultural areas, crop residues (such as
sugarcane stalks, rice husks, and corn cobs) and
animal manure are collected and burned.
– About 2.7 billion people in 77 less-developed
countries face a fuelwood crisis and are often forced
to meet their fuel needs by harvesting wood faster
than it can be replenished.
– Plant fast-growing trees, shrubs, and perennial
grasses in biomass plantations, but this can deplete
soil nutrients and deplete or degrade biodiversity.
We can convert plants and plant
wastes to liquid biofuels
• Liquid biofuels such as biodiesel (produced from
vegetable oils) and ethanol (ethyl alcohol
produced from plants and plant wastes) are
being used in place of petroleum-based diesel
fuel and gasoline.
• Advantages of biofuels:
– While oil resources are concentrated in a small
number of countries, biofuel crops can be grown
almost anywhere, and thus they help countries to
reduce their dependence on imported oil.
We can convert plants and plant
wastes to liquid biofuels
– If these crops are not used faster than they are
replenished by new plant growth, there is no net
increase in CO2 emissions, unless existing grasslands
or forests are cleared to plant biofuel crops.
– Biofuels are easy to store and transport through
existing fuel networks and can be used in motor
vehicles at little or no additional cost.
• The two most water-intensive ways to produce a
unit of energy are irrigating soybean crops to
produce biodiesel fuel and irrigating corn to
produce ethanol.
We can convert plants and plant
wastes to liquid biofuels
• An alternative to corn ethanol is cellulosic ethanol,
which is produced from inedible cellulose that
makes up most of the biomass of plants.
– In this process, enzymes are used to help convert the
cellulose from widely available inedible cellulose
materials such as leaves, stalks, and wood chips to
sugars that are processed to produce ethanol.
– A plant that could be used for cellulosic ethanol
production is switchgrass, a tall perennial grass native
to North American prairies that grows faster than corn.
– Affordable chemical processes for converting cellulosic
material to ethanol are still being developed and are
possibly years away.
We can get energy by tapping
the earth’s internal heat
• Deep geothermal energy stored in hot, dry
rock found 5 or more kilometers (3 or more
miles) underground almost everywhere.
– Tapping just 2% of this source of geothermal
energy in the U.S. could produce more than
2,000 times the country’s current annual use
of electricity.
– Digging so deep into the earth’s crust is
costly.
Choosing energy paths
• Energy policies need to consider the future.
– Usually takes at least 50 years and huge investments to
phase in new energy alternatives.
• Creating energy policy involves trying to answer
the following questions for each alternative:
– How much of the energy resource is likely to be
available in the near future (the next 25 years) and in
the long term (the next 50 years)?
– What is the estimated net energy yield (p. 000) for the
resource?
– What are the estimated costs for developing, phasing in,
and using the resource?
Choosing energy paths
– What government research and development subsidies
and tax breaks will be needed to help develop the
resource?
– How will dependence on the resource affect national
and global economic and military security?
– How vulnerable is the resource to terrorism?
– How will extracting, transporting, and using the resource
affect the environment, the earth’s climate, and human
health? How will these harmful costs be paid and by
whom?
– Does use of the resource produce hazardous, toxic, or
radioactive substances that must be safely stored for
very long periods of time?
Choosing energy paths
• Hard energy paths are based on increasing
use of nonrenewable fossil fuels and nuclear
energy.
• Soft energy paths are based on improving
energy efficiency and increasing the use of
various renewable energy resources.
Choosing energy paths
• Energy policies need to consider the future.
– Usually takes at least 50 years and huge investments to
phase in new energy alternatives.
• Creating energy policy involves trying to answer
the following questions for each alternative:
– How much of the energy resource is likely to be
available in the near future (the next 25 years) and in
the long term (the next 50 years)?
– What is the estimated net energy yield (p. 000) for the
resource?
– What are the estimated costs for developing, phasing in,
and using the resource?
Choosing energy paths
– What government research and development subsidies
and tax breaks will be needed to help develop the
resource?
– How will dependence on the resource affect national
and global economic and military security?
– How vulnerable is the resource to terrorism?
– How will extracting, transporting, and using the resource
affect the environment, the earth’s climate, and human
health? How will these harmful costs be paid and by
whom?
– Does use of the resource produce hazardous, toxic, or
radioactive substances that must be safely stored for
very long periods of time?
Choosing energy paths
• Hard energy paths are based on increasing
use of nonrenewable fossil fuels and nuclear
energy.
• Soft energy paths are based on improving
energy efficiency and increasing the use of
various renewable energy resources.
Choosing energy paths
– A combination of greatly improved energy
efficiency and the temporary use of
nonrenewable natural gas will be the best way
to make the transition to a diverse mix of
renewable energy resources over the next
several decades
– Because of their still-abundant supplies and
artificially low prices, we will continue using
fossil fuels in large quantities.
Bioenergy power plants
Wind farms
Small solar-cell
power plants
Fuel
cells
Solar-cell
rooftop
systems
Rooftop solarcell arrays
Smart electrical
distribution
system
Commercial
Small
Residential wind
turbine
Industrial
Microturbines
Fig. 13-47, p. 342
Bioenergy power plants
Wind farms
Small solar-cell
power plants
Fuel
cells
Solar-cell
rooftop
systems
Rooftop solarcell arrays
Smart electrical
distribution
system
Commercial
Small
Residential wind
turbine
Industrial
Microturbines
Fig. 13-47, p. 342
Increasing heat and carbon content
Increasing moisture content
Lignite
Peat
(brown coal)
(not a coal)
Anthracite
(hard coal)
Bituminous
(soft coal)
Heat
Heat
Heat
Pressure
Pressure
Pressure
Partially decayed plant
matter in swamps and
bogs; low heat content
Low heat content; low
sulfur content; limited
supplies in most areas
Extensively used as a fuel
because of its high heat
content and large supplies;
normally has a high sulfur
content
Highly desirable fuel
because of its high heat
content and low sulfur
content; supplies are
limited in most areas
Stepped Art
Fig. 13-12, p. 310
Nuclear fuel cycle
Decommissioning
of reactor
Fuel assemblies
Enrichment
of UF6
Fuel fabrication
Conversion
of U3O8
to UF6
Reactor
(conversion of enriched UF
6
to UO2 and fabrication of
fuel assemblies)
Uranium-235 as UF6
Plutonium-239 as PuO2
Temporary storage
of spent fuel
assemblies underwater
or in dry casks
Spent fuel
reprocessing
Low-level radiation
with long half-life
Mining uranium
ore (U3O8)
Open fuel cycle today
Recycling of nuclear fuel
Geologic
disposal of
moderateand high-level
radioactive
wastes
Fig. 13-18, p. 315
How commercial energy flows
through the US economy
Energy Inputs
System
Outputs
9%
7%
41%
83%
U. S.
economy
43%
9%
4%
4%
Nonrenewable fossil fuels
Nonrenewable nuclear
Hydropower, geothermal,
wind, solar
Biomass
Useful energy
Petrochemicals
Unavoidable energy loss
Energy waste
Fig. 13-23, p. 321
Conventional hybrid
Fuel tank
Battery
Internal
combustion
engine
Transmission Electric motor
Fig. 13-27a, p. 325
Plug-in hybrid
Fuel tank
Battery
Internal
combustion
engine
Transmission
Electric motor
Fig. 13-27b, p. 325
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. 13-27, p. 325
You can takes steps to save
energy and money
Will hydrogen save us?
• Focus is on fuel cells that combine H2
and oxygen gas (O2) to produce
electricity and water vapor (2 H2 +
O2→2 H2O).
• Use of hydrogen as a fuel would eliminate
most of our outdoor air pollution problems.
• Greatly reduce the threat of projected
climate change as long as the H2 is not
produced with the use of fossil fuels or
nuclear power.
Will hydrogen save us?
• Three challenges in turning the vision of
widespread use of hydrogen as a fuel into
reality.
– Hydrogen gas must be produced from elemental
hydrogen (H), which requires using other forms of
energy; the amount of energy it takes to make this
fuel will always be more than the amount we can get
by burning it.
– Fuel cells are the best way to use H2 to produce
electricity.
– Whether or not a hydrogen-based energy system
produces less outdoor air pollution and CO2 than a fossil
fuel system depends on how the H2 is produced.
Will hydrogen save us?
• Possible uses of hydrogen fuel:
– Fuel-cell cars, running on affordable H2
produced from natural gas, could be in
widespread use by 2030 to 2050.
– Larger, stationary fuel cells could provide
electricity and heat for commercial and
industrial users.
– In homes, a fuel-cell stack about the size of a
refrigerator could provide heat, hot water, and
electricity.
Using hydrogen has advantages
and disadvantages