ESC110 CHAPTER TWELVE
ENERGY
Chapter Twelve Readings & Objectives
Required Readings
Cunningham & Cunningham, Chapter Twelve: Energy
At the end of this lesson, you should be able to:
•summarize our current energy sources and explain briefly how our energy
compares with that of other people in the world;
•analyze the resources and reserves of fossil fuels in the world;
•evaluate the costs and benefits of using coal, oil, and natural gas;
•understand how nuclear reactors work, why they are dangerous, and how they
might be made safer;
•appreciate the opportunities for energy conservation available to us;
•understand how active and passive systems capture solar energy, and how
photovoltaic collectors generate electricity;
•comprehend the promise and problems of using biomass as an energy source;
and,
•explain how hydropower, wind, and other energy from the earth’s forces can
contribute to our energy supply.
Chapter Twelve Key Terms
 active solar systems page 286 of text
 chain reaction 281
 control rods 281
 energy 275
 fossil fuels 275
 fuel assembly 281
 fuel cells 290
 gasohol 293
 "green pricing” 290
 high-level waste repository 255
 joule (J) 275
 monitored, retrievable storage 283
 nuclear fission 281
 passive heat absorption 286
 power 275
photovoltaic cell 288
Proven-in-place reserves 277
 reformer 290
 wind farms 294
 work 275
Chapter Twelve Topics
• Energy Sources and Uses (Oil & Arctic
National Wildlife Refuge)
• Fossil Fuels
• Nuclear Power
• Energy Conservation (Hybrid Autos)
• 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.
Energy Use Trends
• 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.
Per Capita Energy Use & GNP
U.S. Energy Flow, 1999
Quantities in Quadrillion BTUs.
PART 2: FOSSIL FUELS
• 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 Reserves
Natural Gas Reserves
Recoverable Oil Reserves
Coal Extraction and Use
• 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:
–
–
–
–
–
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.
• 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
• 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
Chernobyl
1986
Three Mile Island
1979
Radioactive Waste Management
• 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.
To be effective with
domestic energy
conservation buying
energy-efficient
appliances and using
innovative ways to
insulate your home can
significantly cut your
energy consumption. To
left is earth-sheltered
house in Taos, New
Mexico - an effective way
to insulate your house.
PART 5: SOLAR ENERGY
• 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.
Underground massive
heat storage unit
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 heatabsorbing 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 steamturbine 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
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.
Costs for alternative and renewable
energy sources have dropped in
recent years. Nuclear energy costs
have increased the most.
PART 6: FUEL CELLS
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•
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•
•
•
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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?
Average Daily
Solar Radiation
Solar radiation units of the legend
are langleys
[a langley = 1 calorie/cm2 (3.69Btu/ft2)]