2. Chapter 12 Topics
• 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?
3. 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 1o
C, whereas a British Thermal Unit (BTU) is
the energy needed to heat 1 pound of water 1o
F
– 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.
6. 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.
7. 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 & GDP
8. 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
10. 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)
11. 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.
12. Natural Gas Consumption
• 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.
•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.
13. 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.
14. 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 neutron-
absorbing 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.
16. 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.
18. 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.
19. PART 4: ENERGY CONSERVATION
Hybrid gas-electric automobile
20. ENERGY CONSERVATION
– Most potential energy in fuel is lost as waste heat.
– In response to 1970’s oil prices, average US automobile gas-
mileage 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 three-
fourths 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.
21. 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 heat-
absorbing 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.
22. 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.
23. 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
26. 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
27. •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.
Promoting Renewable Energy
28. PART 6: FUEL CELLS
• 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.
30. 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.
31. 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.
32. 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.
34. 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.
35. PART 8: ENERGY FROM EARTH'S FORCES
• Water power produces 25%
of the world’s electricity and
it is clean, renewable
energy.
• Dams cause social and
ecological damage.
Wind
Geothermal
Tidal
Wave
Hydropower
36. • 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
37. 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
38. This energy source
involves the use of
high-pressure, high-
temperature steam
fields that exist
below the earth’s
surface.
Geothermal Energy
39. 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/low-
tide 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.
This slide set includes material from Chapter 12 Environmental Science. The subject of this chapter is energy.
"Talk doesn't cook rice." I particularly like this Chinese proverb because it puts in perspective the requirement of society to acquire and utilize energy either through the use of fire, animals, or machines. This is one of the most unique characteristics of humans. There are multiple sources of potential energy and uses for that energy. These include fossil fuels, nuclear power, solar energy, biomass, energy from the Earth's interior, and other sources of energy. The conservation of energy that is already available, the development of new energy sources and energy for future uses will continue to be major sources of challenges for society.
A few definitions are in order. First, work is the application of force moving mass through a distance. Anyone who has ever pushed a wheelbarrow full of dirt for any distance should understand this definition. When we carry backpacks full of camping gear to the top of a mountain we do work.
Energy is the capacity to do work; however, that energy must be channeled in such a way as to move mass to do the actual work. Most of the machines that humans construct are simply mechanisms that allow potential energy to become kinetic and do useful work.
Power is the rate at which energy is consumed, including the rate at which work is done. For instance, the horsepower of a car gives a measure of the ability of the engine to accelerate the mass of the car initially and to keep the car moving against the fractional forces of air, the road, and parts of the engine rubbing against each other. The definitions of calorie and BTU are contrasts of the metric with the English systems of measurement. The definition in the slide is for what is called a small or gram calorie. A large or kilogram calorie (amount of energy needed to heat 1 kilogram 1oC) is of more use in a comparative sense with a Btu since 2.2 lbs equals a kilogram. A large calorie is what is used to measure energy produced by food when oxidized in our bodies. We'll apply our definition of joule in the next slide.
Above are energy terms from a table in our text. If you can apply yourself to relating joules to watts and understand the meaning of calorie (and its English equivalent - Btu), these units will fall into place. This is because the rest of what is needed to understand energy units hinges on prefixes such as kilo, mega, giga and peta. A 100 Watt (W) light bulb uses 100 joules of electricity every second. To lower your utility bill you might want to switch from 100 to 60W bulbs in areas that only need to be dimly lighted.
Since energy is always required to do useful work, the production of energy is one of the most important efforts made by society. Fossil fuels are derived from organic material produced from biomass derived from the process of photosynthesis many millions of years ago. This organic material that was built up in geological deposits over long periods of time are today the primary source of energy for society, accounting for about 79% of all commercial energy in the world. Of the major three fossil fuels (oil, coal and gas), oil is the most important energy source. Oil accounts for 35% of total world energy production. Nuclear makes up 7%. Biomass fuels account for 9.5% of total commercial and energy production. Other renewables such as solar, wind and hydro account for 4.5% of the total. This shows that total renewables (biomass, hydro, etc.) provide 14% of the energy.
In the United States, there is a relative balance between the use of energy by industry, residences, and transportation. 3 trillion passenger miles and 600 billion ton miles of freight are carried annually by U.S. motor vehicles. One very important aspect of energy use is the inefficiency of conversion of primary fuels, such as coal, into more useful forms such as electricity. On the average, fully half of the energy in primary fuels is lost in conversion. Much of research on energy is spent on trying to make systems for conversion of energy from one form into another more efficient form.
Higher energy use correlates well with a higher standard of living for people living within a country. When the energy is very cheap, like in the U.S., there is a tendency to waste it. There is little question that a mile driven in a highly fuel-efficient car moves people just as effectively as a mile driven in a mega-SUV that probably gets only half the gas mileage; yet, the higher use of gasoline and higher price of the SUV both lead to a higher GNP per person here. Obvious is the relative consumption of energy in the U.S. and Canada (average people use 300 times as much energy) vs. the poorest countries in the world. It's unlikely, that the average American can justify this incredibly wasteful use of energy. The richest 20 countries consume nearly 80% of natural gas, 65% of oil, and 50% of coal production annually. On average, each person in the U.S. and Canada uses more than 300 gigajoules (GJ) of energy annually. In poorest countries of the world, each person generally consumes less than one GJ annually.
This figure shows energy consumption per capita divided by the GNP per capita of some countries. Ones above the blue line are relatively high in terms of their use of energy relative to their production of goods and services. Notice that the European countries, where energy is a very expensive, have very high efficiencies in terms of producing wealth with a given amount of energy. Notice Switzerland, with a much higher income per capita than the U.S., has a smaller use of energy. Some countries have high utilization of energy for producing much smaller amounts of wealth. Russia has a higher consumption per capita than Switzerland, but a low per-capita GNP.
It's hard to overemphasize how important fossil fuels are to present energy production, and the temporary nature of this use. Fossil fuels are organic chemicals created by living organisms millions of years ago. The oxygen in our atmosphere represents the conversion of carbon dioxide into these organic materials. If we burn all of the fossil fuels that were ever created, this would theoretically consume all the oxygen in the Earth's atmosphere. However, its likely impossible to recover all of Earth's potential fossil fuels either because they are inaccessible or so diluted that they're not useful as a fuel. Since fossil fuels took millions of years to create, they also would take millions of years to replace. Society is consuming fossil fuels at a rate many times that of replacement.
As fossil fuels become less available and global consumption increases, more marginal, difficult and sensitive areas are drilled. One such area is offshore oil wells such as the one shown on this slide. In the process of extracting oil, natural gas is released. This gas is burned off as excess and is shown here as the flame on the left side of the platform.
The supply of coal in the world is about 10 times greater than oil and gas combined. Much of the coal of the world is located in North and Central America, Asia, and Europe. Coal represents the fossil fuel with the highest reserves relative to the amount presently used. It is likely that coal reserves in the world could supply energy for human use for 200 years at the present consumption rate.
Today, oil is the primary energy source throughout the world, as well as one of the primary contributors to political problems. A single country, Saudi Arabia, has about one quarter of the known supplies of oil in the world, over 10% of recoverable oil reserves are in the volatile Mideastern countries. Interestingly, the nations of the world with the largest amounts of all oil are among the most politically troubled. For instance, Saudi Arabian nationals comprised most of those primarily responsible for the destruction of the World Trade Center in the U.S., the country to which Saudi Arabia sends the largest amount of its oil exports. The countries of Iraq, Iran, Kuwait, and Venezuela also do not rank among the most stable economies or governments in the world and they have much of the earth's oil reserves.
Natural gas, the third most important fossil fuel, has the largest reserves located in the former U.S.S.R. and the Middle East. Natural gas produced from Canada and internally within the United States is one of the main sources of heating fuel for Seattle. Natural gas is extremely efficient to utilize, but very difficult to store and move.
The extraction and use of coal creates considerable damage to the environment, as well as to the people that mine coal. My uncle Ted, for instance, is on a disability for black lung caused by breathing coal dust when he was a miner in West Virginia. Just about anyone from West Virginia or Western Virginia is likely to know someone employed by and harmed by the coal industry. Just recently, there was a mine explosion in China that killed over 200 people. Strip mining, which is much safer than tunnel mining, destroys the ground above coal deposits. The waste materials produced from coal also clog streams, rivers and the land on which the spoils are placed. When coal is burned, it releases large amounts of air pollution, including sulfur dioxide (a contributor to acid rain, nitrous oxides, and particulates.
World coal deposits are vast, ten times greater than conventional oil and gas resources combined. Total resource is estimated at 10 trillion metric tons. Proven-in-place reserves should last about 200 years. Coal is a dirty and dangerous energy resource. Thousands die annually from respiratory diseases directly attributable to coal mining. The major cause of health problems from coal mining is black lung disease (an inflammation and fibrosis caused by accumulation of coal dust in the lungs or airways).
Acquiring and utilizing oil leads to significant environmental and other problems. The combustion of all oil leads to substantial air pollution and is the source of nearly all air pollution in Seattle. The drilling and pumping of oil causes significant environmental problems, both from the pollution of oil that leaks into soil, streams, and oceans and also due to the necessity to move oil around the world. The infrastructure associated with the oil industry also creates considerable controversy and problems, including problems associated with drilling and then moving the oil, such as through pipelines. As oil becomes depleted and prices rise, it will likely become more economical to find and bring other deposits to market. This would mean increasing pressure to drill in environmentally controversial areas such as ANWR and off the California coast.
Estimates of total oil supply usually do not reflect large potential from unconventional oil sources such as shale oil and tar sands. These could potentially double total reserves. There are severe environmental costs to retrieving shale oil and tar sands including factors such as toxic sludge production and the immense use of water required.
Because of the energy produced by hydrogen combustion as well as carbon combustion in the molecules of natural gas, its utilization is almost twice as efficient as coal in term of carbon dioxide. In many cases, because of the difficulty of storage and transportation, natural gas is flared off during oil pumping, which is the wasteful problem that also results in additional air pollution.
Nuclear-Power has major advantages over the consumption of fossil fuels as sources of energy. However, nuclear power has almost completely lost its support and in the United States it only comprises about 7% of the U.S. energy production. Safety concerns associated with nuclear power production and the ultimate disposal of nuclear wastes all are among the primary concerns of nuclear energy. Also, given the September 11th, 2001 destruction of the World Trade Center by terrorists, the potential for loss of nuclear fuel that could be used to construct a bomb utilized by terrorists, or a dirty bomb (that would scatter radioactive material) are probably well justified.
One of the major concerns to nuclear safety is the susceptibility to terrorists attacks from dirty bombs that could spread radioactivity over large areas of metropolitan areas.
This includes some description of the basicThe next slide gives a schematic of this process.
The process by which nuclear fission occurs is relatively simple. An unstable radioactive element such as uranium-238 splits, and molybdenum and tin (new elements) are formed. In the process, two neutrons and heat are emitted. The neutrons move at very high rates of speed from the reaction point, potentially slamming into another atom of uranium-235. When this occurs, the atom of uranium impacted also splits, and a process called a chain reaction can take place as new uranium atoms release new neutrons, and those neutrons split additional uranium atoms. The key to successful production of nuclear energy is to contain this extremely powerful reaction and derive useful energy from it. An uncontrolled chain reaction creates a nuclear bomb.
A skematic of a PWR is shown on the next slide.
The design of a modern nuclear reactor utilizes the intense heat from fission to boil water, which drives a steam turbine in the same way steam engines that built over a hundred years ago work. Generally, the steam turbine runs a generator, and electricity is produced by the nuclear power plant as its primary product.
One of the most contentious problems associated with nuclear power is the disposal of wastes. In the United States, the ultimate answer has been put off for decades and Congress has actually practiced "feint-of-hand" in dealing with nuclear waste issues. For instance, I worked for two years at Oak Ridge National Laboratory as an Environmental Scientist. During the Manhattan Project, which produced the first nuclear weapon, many thousands of tons of nuclear waste were buried in trenches, called SWBA's, or solid waste burial areas. These sat in place for decades, and Oak Ridge was littered with areas labeled as SWBA this and that. Around 1996 Congress passed a law dictating that all nuclear waste would be stored, not disposed of, until they decided how to dispose of it. A major expense and effort at Oak Ridge was to go back and substitute the letter S for the letter B on those signs, and in documents on the sites. Nothing changed but the designation of the areas, which were now storage areas instead of burial areas. This was considered a significant step forward in how the United States dealt with its nuclear waste. Recently, the United States has centered on Yucca Mountain in Nevada as the center for receiving its high level radioactive waste.
Methods of disposing of nuclear wastes include ocean dumping, dry cask storage and the search for a long-term national depository.
Energy conservation offers the potential for saving considerable amounts of energy and has the added advantage of not having the environmental problems associated with producing that energy. A good example is the American automobile, which uses a considerable amount of energy to operate. Automobiles that have higher fuel efficiency in mpg can greatly reduce the amount of oil that the U.S. requires. The U.S. more than doubled its average fuel efficiency from 13 mpg in 1975 to 29 mpg in 1988. Unfortunately, the popularity of trucks, sport-utility vehicles, and heavier vehicles in general allowed in the average mpg to slip to 24 mpg by the year 2000. Technology has had a considerable impact on the potential for high mileage automobiles. For instance, the Honda Insight and the Toyota Prius are able to get greater than 50 mpg in city driving because of the combination of an electric and gasoline engine.
Interestingly, vehicles such as the Prius have become the latest status symbol for showing your environmental conscience. They are more than twice as expensive as cars that get nearly the same mileage (i.e. Toyota Echo). The true measure of conservation lies in driving less and more efficiently, not just in driving the latest status symbol. Note, for instance, the house in the background, which appears to be the typical American huge status symbol. This picture shouts “you can still have it all” and not impact the environment…just buy a brand new Prius.
The easiest, most efficient and effective way to solve our energy dilemma is to improve energy conservation practices and techniques. It all means less pollution, less dependence on foreign imports and healthier people.
Seattle is not famous for the large amount of sun that it receives. Other parts of the United States, however, receive larger amounts of insolation that can be utilized as an energy source. The amount of sun that this area receives is such that the cost of efficiently utilizing solar energy (through systems installation) is out-competed by very cheap energy sources available from fossil fuels.
Commercial systems for converting sun energy into commercial energy have already been developed, but are still relatively expensive compared to fossil sources. In the system above, energy can be focused onto a small area to boil water and drive a steam generator.
The good news for photovoltaic solar energy is that costs continue to decrease. For many remote sites, agencies have already conceded that solar panels are cheaper and easier to maintain than large 12 volt batteries.
Note that in the figures on this slide solar radiation is limited in the Pacific Northwest and the Northeast summer, and more so, in the winter. This points to the fact that an alternative energy future will require that each region and even municipality carefully consider energy options that will work for their particular needs and situation.
Here is an example of photovoltaic cells which convert sunlight directly into electricity. The system works as follows. The upper layer is made of crystal silicon with boron impurities, and this setting causes electrons to be released when solar radiation hits the upper layer of the cell. These released or free electrons move into the lower layer of the cell. A positive, thus, is left behind in the upper silicon layer. A negative charge is now in the lower layer due to an abundance of electrons. The difference in charge creates an electric current in a wire connecting the two layers. This current can be intercepted to burn a light or due some other type of work before returning to the cell.
As we depend more on diffuse energy sources such as hydro, wind and solar, the efficient transmission to transport the electricity to where it is needed becomes more and more of a challenge. Transmission lines are unsightly and create large electromagnetic fields whose effect on humans is unknown. You might have skied beneath the electrical towers at Stevens pass and noticed your body respond to the electrical current in the air there. It is not the most beautiful outdoor setting, but the snow is still great. One new transport method currently being researched is to use the on sight electricity to hydrolyze water. The hydrogen split off from the water molecule can then be transported in tanks to be used in fuel cells in urban and industrial areas. See the text for other innovative solutions to energy transport and storage.
This figure shows some of the relative costs of producing commercial energy from several sources. In many cases, the cost of producing energy associated with alternative systems are dropping quickly relative to the cost of traditional sources such as fossil fuels and nuclear power. The U.S. continues to subsidize the traditional sources of fossil fuels, nuclear, and hydropower at much greater rates than investment in alternative systems.
Ultimately, energy might be stored and utilized at the place where it is required by the use of fuel cells. Fuel cells use hydrogen and potentially other gases by converting them directly into electricity. For the hydrogen system, the product of the reaction is water. Seattle is a major source of fuel cell research and production.
Current is proportional to the size of the electrodes, while voltage is limited to about 1.23 volts/cell. Fuel cells can be stacked together until the desired power level is achieved.
Biomass, particularly agricultural waste products and unharvested forest products, also offer a source of energy. For instance, more than 100 years ago in this region, fire wood was the primary way in which homes were heated. The Rob Harrison household partially heats its home with firewood by use of a highly efficient wood stove. The stove we use is specially designed not to emit a large amount of pollution often identified with fireplaces and old-style airtight wood stoves. One of the major reasons for the creation of the U.S. Forest Service was to assure a continuous supply of wood products in a United States that was largely deforested, at least in the east. Lack of firewood for home heating was considered to be a crisis at one time in U.S. history.
Wood provides < 1% of U.S. energy but up to 90% in poorer countries. 1,500 million m3 of fuelwood is collected in the world annually. Inefficient burning of wood produces smoke laden with fine ash, soot, hazardous carbon monoxide (CO), and hydrocarbons; however, wood combustion produces fewer sulfur gases and burns at lower temperature than coal.
If you are having trouble making ends meet, as many people in developing countries do, then you are very unlikely to worry about the long-term environmental implications of over harvesting wood. This is especially true if the wood is being used to cook meals for your family and warm your house. This will become more apparent with the discussion presented in the next slide.
Currently, about half of worldwide annual wood harvest is used as fuel. Eighty-five percent of fuelwood 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. This problem intensifies as less developed countries continue to grow. For urban dwellers, the opportunity to scavenge wood is generally nonexistent.
The fuelwood crisis in less developed countries of the world is even more critical. For instance, in Karatu, Tanzania, where Rob worked as a peace Corps volunteer, there was no firewood available near the village. Villagers had to walk considerable (and growing) distances to native forests several kilometers away from the village. Rob's job was to try and get them to grow trees closer to home, which would improve the quality of their life and reduce the destruction of the native forests nearby. Notice also how small the trees in the bundles these African women are carrying are. If the trees were allowed to grow even an additional year, the productivity of the area harvested would be much greater per year.
In areas that have no woody vegetation, either because they have been deforested or because they naturally do not support trees, dung burning is practiced. This is a particularly serious problem because using dung as fuel destroys the nutrients in the animal waste and thus reduces soil fertility. Not returning animal dung to land as fertilizer reduces crop production and food supplies.
Waste materials can be used to produce methane, which is effectively the same as natural gas in that it can be distributed directly to and utilized within homes. For instance, the figure presented here shows a methane converter that converts organic material into methane. These can be built on very small scales, such as for an individual home, or on much larger scales to fuel industrial systems.
Methane is the main component of natural gas. It is produced by anaerobic decomposition. Burning methane produced from manure provides more heat than burning dung itself. Left-over sludge from bacterial digestion is a nutrient-rich fertilizer.Methane is clean, efficient fuel. Municipal landfills contribute as much as 20% of annual output of methane to the atmosphere. Rarely is this landfill methane collected and used as energy for humans. Atmospheric methane is a very potent greenhouse gas, much more so than carbon dioxide.
Liquid fuels such as alcohol can also be produced from biomass and are a very important source of automobile fuel in the United States. This fuel is made by mixing ethanol alcohol with gasoline, creating gasohol. Much of the gasoline sold in the U.S. during the winter includes alcohol added to reduce emissions, which is an added benefit. In the case of the country of Brazil, which has millions of acres of sugar cane plantations, ethanol is produced to directly fuel automobile operation. When I spent one year in Brazil on sabbatical from 1995 to 1996 the car we bought, a Fiat, had an alcohol-powered engine. The exhaust from the engine smelled like a Brazilian mixed drink called a Caipirinha.
Energy from the earth's sources include wind, geothermal, tidal, wave and hydro power. Wind and hydro are really extensions of solar energy since wind and the water cycle are run by solar energy. Hydropower is a major source of energy, particularly in the Pacific Northwest. Hydropower is commonly called a traditional source of energy in the United States because its commercial use is very old, and it produces a large amount of all the worlds electricity: 25 percent. Clearly, hydropower is a clean, renewable energy in most respects. However, dams have other environmental impacts, including blocking the migration of fish species such as salmon, and warming water, which can change the species composition. The destruction of naturally flowing waterways by damming is also a major environmental issue. Remember the Hetch Hetchy Valley as the major issue that destroyed the friendship and cooperation of John Muir and Gifford Pinchot.
Hydropower is an environmental dilemma - clean fuel, but still with many environmental problems.
It is estimated that 20 million MW of wind power could be commercially tapped worldwide. This is fifty times the current power generated by nuclear energy. Typically these operate at 35% efficiency under field conditions. Under normal conditions, (min. 15 km/hr) electric prices typically run 5 cents per kilowatt hour. The standard modern turbine uses only two or three blades in order to operate better at high wind speeds.
The potential for utilizing wind energy is considerable. Presently, California has 90% of all existing wind power generators. There are two reasons for this: 1) the fact that energy is much more expensive in California than in most other states, and 2) with a very powerful economy, California has chosen to invest more in wind power than any other state in the United States. The state of Washington has plans to build a first wind farm near Walla Walla, Washington in one of the most windy areas of the state. Considerable potential exists for developing other commercial wind farms within the state of Washington and elsewhere in the Pacific Northwest.
Wind Farms - Large concentrations of wind generators producing commercial electricity. Negative Impacts include:
Interruption of view in remote places
Destruction of sense of isolation
Potential to kill birds
Geothermal energy is an important energy source in only a few areas, particularly in the country of Iceland which derives most of its energy from geothermal sources. The utilization of geothermal energy in the United States is only on a small-scale, and is likely to remain so considering that the primary areas that would be capable of hosting economical energy plants are environmentally sensitive. Could you imagine, for instance, Yellowstone National Park being replaced by Geothermal Energy, Inc.?
High-pressure, high-temperature steam fields exist below the earth’s surface. Recently, geothermal energy has been used in electric power production, industrial processing, space heating, agriculture, and aquaculture. Geothermal sources have a long life span, involve no mining needs, and there is little waste disposal. Potential dangers include exposure to noxious gases and noise problems from steam valves.
Most of the solar energy entering the earth system is adsorbed by the world's oceans. The production of waves and the Earth's tides also have the potential for producing usable power. The total flow of tide through the Bay of Fundy, which has some of the world's greatest tides, could theoretically produce the energy output of 250 large nuclear power plants. There are potentially large-scale environmental impacts of such projects, as tidal areas include some of the most productive ecosystems in the world.
Futurists have gone so far as to envision a United States with a renewable, alternative energy future. Instead of coal, oil, and other fossil fuels making almost the entire source of energy, biomass, wind, and other renewable resources would make up a large amount of the energy utilized.
One important aspect of producing commercial energy is the amount of land required to produce a particular amount of energy. For instance, the amount of land required to produce an equivalent amount of energy is nearly five times as much for coal energy as for wind energy. Such considerations could be very important if the land utilized is extremely important for other societal benefits, including agriculture or environmental reasons.
