CHAPTER 12: ENERGY
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Chapter 12 Topics
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Energy Sources and Uses
Fossil Fuels
Nuclear Power
Energy Conservation
Solar Energy
Fuel Cells
Biomass
Energy From the Earth’s Forces
What’s Our Energy Future?
PART 1: ENERGY SOURCES AND USES
• Work is the application of force through a distance.
• Energy is the capacity to do work.
• Power is the rate of flow of energy, or the rate at
which work is done.
– A small calorie is the metric measure of energy necessary to heat
1 gram of water 1oC, whereas a British Thermal Unit (BTU) is
the energy needed to heat 1 pound of water 1oF
– A joule is the amount of work done by a force needed to
accelerate 1 kilogram 1 meter per second per second. Another
definition for joule is the force of an electrical current of 1
amp/second through a resistance of 1 ohm.
Worldwide Commercial Energy Production
How We Use Energy
• What are the commercial uses of energy?
– Industry uses 38%;
– Residential and commercial buildings use 36%; and,
– Transportation uses 26%.
• Half of all energy in primary fuels is lost during conversion to more
useful formsm while being shipped or during use.
– Nearly two-thirds of energy in coal being burned to generate
electricity is lost during thermal conversion in the power plant.
Another 10% is lost during transmission and stepping down to
household voltages.
• Natural gas is the most efficient fuel.
– Only 10% of its energy content is lost during shipping and
processing. Ordinary gas-burning furnaces are about 75% efficient.
High-economy furnaces can be 95% efficient.
Per Capita Energy Use & GDP
Energy Use Trends
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A general trend is for
higher energy use to
correlate with a
higher standard of
living
In an average year,
each person in the
U.S. and Canada
consumes more than
300 times the
amount of energy
consumed by a
person in one of the
poorest countries of
the world; however,
Several European
countries have
higher living
standards than the
U.S., yet they use
about half as much
energy.
PART 2: FOSSIL FUELS
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Fossil fuels are organic chemicals created by living organisms that were buried
in sediments millions of years ago and transformed to energy-rich compounds.
Because fossil fuels take so long to form, they are essentially nonrenewable
resources.
 Coal
 Oil
 Natural Gas
Coal
Oil
Natural Gas
Coal Extraction and Use
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Mining is dangerous to humans and
the environment
Coal burning releases large
amounts of air pollution, and is the
largest single source of acid rain in
many areas.
Economic damages are billions of
dollars
900 million tons of coal are burned
in the U.S. for electric power
generation. As a result, multiple
pollutants are released such as:
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Sodium Dioxide (18 million metric
tons)
Nitrogen Oxides ( 5 million metric
tons)
Particulates (4 million metric tons)
Hydrocarbons (600,000 metric tons)
Carbon Dioxide (1 trillion metric
tons)
Oil Extraction and Use
• The countries of the Middle East control two-thirds of all
proven-in-place oil reserves. Saudi Arabia has the most.
• The U.S. has already used up about 40% of its original
recoverable petroleum resource.
• Oil combustion creates substantial air pollution.
• Drilling causes soil and water pollution.
• Often oil contains a high sulfur level. Sulfur is corrosive, thus
the sulfur is stripped out before oil is shipped to market.
• Oil is primarily used for transportation providing > 90% of
transportation energy.
• Resources and proven reserves for the year 2000 are 650
billion barrels (bbl). 800 bbl remain to be discovered or are
currently not recoverable.
Natural Gas Consumption
•World’s third largest commercial fuel (23% of global energy used).
•Produces half as much CO2 as equivalent amount of coal.
•Most rapidly growing used energy source.
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Proven world reserves and
resources of natural gas
equal 3,200 trillion cubic
feet. This equals a 60 year
supply at present usage
rates.
Natural gas produces only
half as much CO2 as an
equivalent amount of coal.
Problems: difficult to ship
across oceans, to store in
large quantities, and much
waste from flaring off.
PART 3: NUCLEAR POWER
• President Dwight Eisenhower, 1953, “Atoms for
Peace” speech.
– Eisenhower predicted that nuclear-powered electrical generators would
provide power “too cheap to meter.”
– Between 1970-1974, American utilities ordered 140 new reactors, but
100 were subsequently canceled.
• Nuclear power now produces only 7% of the U.S.
energy supply.
• Construction costs and safety concerns have made
nuclear power much less attractive than was
originally expected.
– Electricity from nuclear power plants was about half the price of coal
in 1970, but twice as much in 1990.
How Do Nuclear Reactors Work
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The common fuel for nuclear reactors is U235 that occurs
naturally (0.7%) as a radioactive isotope of uranium.
U235 is enriched to 3% concentration as it is processed into
cylindrical pellets (1.5 cm long). The pellets are stacked in
hollow metal rods (4 m long).
100 rods are bundled together into a fuel assembly. Thousands
of these fuel assemblies are bundled in the reactor core.
When struck by neutrons, radioactive uranium atoms undergo
nuclear fission, releasing energy and more neutrons.This result
triggers a nuclear chain reaction.
This reaction is moderated in a power plant by neutronabsorbing solution (Moderator).
Control Rods composed of neutron-absorbing material are
inserted into spaces between fuel assemblies to control reaction
rate.
Water or other coolant is circulated between the fuel rods to
remove excess heat.
Nuclear fission occurs in the core of a nuclear reactor
Kinds of
Reactors
• 70% of nuclear power plants are pressurized water reactors
(PWRs). Water is circulated through the core to absorb heat from
fuel rods. The heated water is then pumped to a steam generator
where it heats a secondary loop. Steam from the secondary loop
drives a high-speed turbine making electricity.
• Both reactor vessel and steam generator are housed in a special
containment building. This prevents radiation from escaping and
provides extra security in case of accidents. Under normal
operations, a PWR releases little radioactivity.
Reactor Design
Radioactive Waste Management
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Production of 1,000 tons of uranium fuel typically generates 100,000
tons of tailings and 3.5 million liters of liquid waste.
– Now approximately 200 million tons of radioactive waste exists in
piles around mines and processing plants in the U.S.
About 100,000 tons of low-level waste (clothing) and about 15,000
tons of high-level (spent-fuel) waste in the US.
– For past 20 years, spent fuel assemblies have been stored in deep
water-filled pools at the power plants. (designed to be temporary).
– Many internal pools are now filled, and a number plants are storing
nuclear waste in metal dry casks outside.
A big problem associated with nuclear power is the disposal of
wastes produced during mining, fuel production, and reactor
operation.
– U.S. Department of Energy announced plans to build a high-level
waste repository near Yucca Mountain Nevada in 1987.
– Cost is $10-35 billion, and earliest opening date is 2010.
– This allows the government to monitor & retrieve stored uranium.
PART 4: ENERGY CONSERVATION
Hybrid gas-electric automobile
ENERGY CONSERVATION
– Most potential energy in fuel is lost as waste heat.
– In response to 1970’s oil prices, average US automobile gasmileage increased from 13 mpg in 1975 to 28.8 mpg in 1988.
Falling fuel prices of the 1980’s, however, discouraged further
conservation.
Energy Conversion Efficiencies
•Energy Efficiency is a measure of energy
produced compared to energy consumed.
–Household energy losses can be reduced by one-half to threefourths by using better insulation, glass, protective covers, and
general sealing procedures. Energy gains can be made by
orienting homes to gain passive solar energy in the winter.
PART 5: SOLAR ENERGY
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Photosynthesis
Passive solar heat is using
absorptive structures with
no moving parts to gather
and hold heat. Greenhouse
design
Active solar heat is when a
system pumps a heatabsorbing medium through
a collector, rather than
passively collecting heat in a
stationary object. Water
heating consumes 15% of
US domestic energy budget.
Mean solar energy striking the upper atmosphere is 1,330 watts per
square meter. The amount reaching the earth’s surface is 10,000 times
> all commercial energy used annually. Until recently, this energy
source has been too diffuse and low intensity to capitalize for electricity
production.
High-Temperature Solar Energy
•Parabolic mirrors (left) are
curved reflective surfaces that
collect light and focus it onto a
concentrated point. It involves
two techniques:
–Long curved mirrors focus
on a central tube containing a
heat-absorbing fluid.
–Small mirrors arranged in
concentric rings around a tall
central tower track the sun
and focus light on a heat
absorber on top of the tower
where molten salt is heated to
drive a steam-turbine electric
generator.
Photovoltaic Solar Energy
• During the past 25 years, efficiency of energy
capture by photovoltaic cells has increased from less
than 1% of incident light to more than 10% in field
conditions, and 75% in laboratory conditions.
– Invention of amorphous silicon collectors has allowed
production of lightweight, cheaper cells.
• Photovoltaic cells capture solar energy and convert it
directly to electrical current by separating electrons
from parent atoms and accelerating them across a
one-way electrostatic barrier.
– Bell Laboratories - 1954
• 1958 - $2,000 / watt
• 1970 - $100 / watt
• 2002 - $5 / watt
Average Daily
Solar Radiation
Solar radiation units of the legend
are langleys
[a langley = 1 calorie/cm2 (3.69Btu/ft2)]
Photovoltaic energy solar energy converted
directly to electrical
current
Transporting & Storing Electrical Energy
• Electrical energy storage is
difficult and expensive.
– Lead-acid batteries are
heavy and have low energy
density.
• Typical lead-acid battery
sufficient to store electricity
for an average home would
cost $5,000 and weigh 3-4
tons.
– Pumped-Hydro Storage
– Flywheels
Promoting Renewable Energy
•Distributional Surcharges
–Small charge levied on all utility customers to help finance research and
development.
•Renewable Portfolio
–Mandate minimum percentage of energy from renewable sources.
•Green Pricing
–Allow utilities to profit from conservation programs and charge
premium prices for energy from renewable sources.
PART 6: FUEL CELLS
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Fuel cells use ongoing electrochemical
reactions to produce electrical current
Fuel cells provide direct-current
electricity as long as supplied with
hydrogen and oxygen.
Hydrogen is supplied as pure gas, or a
reformer can be used to strip hydrogen
from other fuels.
Fuel cells run on pure oxygen and
hydrogen produce only drinkable water
and radiant heat.
Reformer releases some pollutants, but
far below conventional fuel levels.
Fuel cell efficiency is 40-45%.
Positive electrode (cathode) and
negative electrode (anode) separated by
electrolyte which allows charged atoms
to pass, but is impermeable to electrons.
Electrons pass through external circuit,
and generate electrical current.
PART 7: BIOMASS
Fuelwood Crisis
• Currently, about half of worldwide annual wood harvest is used as
fuel.
– Eighty-five percent of fuelwood is harvested in developing countries.
• By 2025, worldwide demand for fuelwood is expected to be twice current
harvest rates while supplies will have remained relatively static.
• About 40% of world population depends on firewood and charcoal
as their primary energy source.
– Of these, three-quarters do not have an adequate supply.
• Problem intensifies as less developed countries continue to grow.
– For urban dwellers, the opportunity to scavenge wood is generally
nonexistent.
Fuelwood Crisis in Less-Developed Countries
• About 40% of the
world’s population
depends on firewood
and charcoal as their
primary energy source.
• Supplies diminishing
• Half of all wood
harvested worldwide is
used as fuel.
Using Dung as Fuel
• Where other fuel is in short
supply, people often dry and
burn animal dung.
• When burned in open fires,
90% of potential heat and
most of the nutrients are lost.
• Using dung as fuel deprives
fields of nutrients and
reduces crop production.
• When cow dung is burned in
open fires, 90% of the
potential heat and most of
the nutrients are lost.
Using Methane As a Fuel
Alcohol from Biomass
• Ethanol (grain alcohol) production could be a solution
to grain surpluses but thermodynamic considerations
question it being practical on a sustainable basis.
Gasohol (a mixture of gasoline and alcohol) reduces
CO emissions when burned in cars. Ethanol raises
octane ratings, and helps reduce carbon monoxide
emissions in automobile exhaust.
• Methanol (wood alcohol)
• Both methanol and ethanol make good fuel for fuel
cells.
PART 8: ENERGY FROM EARTH'S FORCES
Wind
Geothermal
Tidal
Wave
Hydropower
• Water power produces 25%
of the world’s electricity and
it is clean, renewable energy.
• Dams cause social and
ecological damage.
• Hydropower
– By 1925, falling water generated 40% of world’s electric power.
• Hydroelectric production capacity has grown 15-fold, but fossil fuel use
has risen so rapidly that now hydroelectric only supplies one-quarter of
electrical generation.
• Total world hydropower potential estimated about 3 million MW.
– Currently use about 10% of potential supply.
• Energy derived from hydropower in 1994 was equivalent to 500 million
tons of oil. Much of recent hydropower development is in very large
dams.
• Drawbacks to dams include:
– Human Displacement
– Ecosystem Destruction
– Wildlife Losses
– Large-Scale Flooding Due to Dam Failures
– Sedimentation
– Herbicide Contamination
– Evaporative Losses
– Nutrient Flow Retardation
Wind Energy
• Wind power - advantages and disadvantages
• Wind farms - potential exists in Great Plains, along seacoasts and Eastern
Washington
http://www.awea.org/projects/washington.html
Geothermal Energy
This energy source
involves the use of
high-pressure, hightemperature steam
fields that exist
below the earth’s
surface.
Tidal & Wave Energy
•Ocean tides and waves
contain enormous amounts
of energy that can be
harnessed.
–Tidal Station - Tide
flows through turbines,
creating electricity. It
requires a high tide/lowtide differential of
several meters.
–Main worries are
saltwater flooding
behind the dam and
heavy siltation.
–Stormy coasts with
strongest waves are often
far from major
population centers.
Part 9:An Alternative Energy Future?