Evaluating Energy Resources

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Evaluating Energy Resources

• Renewable energy

• Non-renewable energy

• Future availability

• Net energy yield

• Cost

• Environmental effects

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Extracting Energy and Mineral Resources

• Surface, subsurface mines, wells

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Removing Nonrenewable Mineral Resources
Surface mining
Subsurface mining

• Overburden

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Points of View

• Cornucopians - we will not run out of
• non-renewable resources because of
• economics and technology

• Neo-Malthusians - we will run out of
• non-renewable resources (limited
• supply)
• - must control population, conserve

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Supplemental Energy
Solar energy - 99 of all energy
used Supplemental energy - everything else
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History of Supplemental Energyin United States

• Wood through mid-1800s
• Renewable
• Maximum sustained yield limits supply

• Coal replaced wood by 1900

• Oil, natural gas exploited (since mid-1900s)
• 1-oil, 2-natural gas, 3-coal
• - all non-renewable

• Use growing dramatically

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100
Wood
Coal
80
Natural gas
60
Contribution to total energy consumption (percent)
Oil
40
Hydrogen Solar
20
Nuclear
0
2100
2025
1950
1875
1800
Year
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How long will supplies last?

• U.S. (5) uses 25 of energy

• Depends on
• - rate of use
• - discovery of new supplies

• Resource supply lifetime
• - oil - 30-60 years
• - natural gas - 50-200 years
• - coal - 65-900 years

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North American Energy Resources
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Oil Resources

• Petroleum (crude oil)

• Primary recovery - 1/3 recoverable

• Secondary recovery - heavy oil (10)

• U.S. is major oil importer
• - thousands of low-output wells

• Saudi Arabia - largest known reserves
• - supply world for 10 years
• - Alaskan supply - 6 months

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OPEC

• Organization of Petroleum Exporting
• Countries

• Supplies 30 of U.S. oil imports

• 1 Mexico
• 2 Canada
• 3 Venezuela (OPEC member)

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Oil Shale and Tar Sands

• Oil shale
• 3X conventional

• Kerogen
• 25 gallons/ton
• Energy inenergy out

• Tar sands

• Bitumen
• 3X return on energy inputs

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Natural Gas

• 50-90 methane

• Propane, butane
• removed, liquified

• Cleanest burning,
• lowest costs

• Problems leaks,
• explosions

• Unconventional tight sands
• - 1-3 X conventional supply, but expensive

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Coal
Carbon (energy content) and sulfur
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Coal

• Bituminous most abundant (52), but
• high in sulfur

• Anthracite most ideal (high energy, low
• sulfur), but least abundant (2)

• Subbituminous (38) moderate energy,
• moderate pollution potential
• Lignite (8) low energy, low pollution
• potential

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Coal

• Surface versus subsurface mines

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North American Energy Resources
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Coal Mining in United States

• Western surface mines

• Mostly subbituminous, lignite

• Used mostly for generating electricity,
• steel-making industry

• Most used east of Mississippi River

• Transportation vs. volume costs, sulfur
• - slurry pipeline?

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Burning Coal More Cleanly

• Fluidized-Bed Combustion

-calcium sulfate used in dry wall
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Coal Gasification - methane
Raw coal
Recover sulfur
Air or oxygen
Raw gases
Steam
Clean methane gas
O2
2CO
2C Coal

Pulverizer
Recycle unreacted carbon (char)
CO

3H2
CH4

H2O
Methane (natural gas)
Slag removal
Pulverized coal
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Coal Liquefaction - liquid fuels

• Both gasification and liquefaction lose
• 30-40 of energy contained in coal

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Nuclear Energy

• Big question mark in energy industry

• Tremendous potential, plagued by
• safety and cost problems

• 3 ways to produce nuclear power
• 1) conventional nuclear fission reactor
• 2) breeder nuclear fission reactor
• 3) nuclear fusion reactor

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Nuclear Energy

• Use radioactive isotopes

• Isotopes - different forms of same
• element
• - atoms have differing masses
• - e.g. U-238, U-235

• Radioactive - unstable atoms emit
• radiation (rays and particles)

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Nuclear Energy

• Conventional fission reactors

• Uranium-235
• (U-238 common)

• Nucleus split by moving neutron

- Core, heat exchanger, generator
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Reactors in the United States
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Nuclear Energy

• Breeder fission reactors

• Uses plutonium-239 as fuel
• U-238 neutron Pu-239

• Pu-239 fissioned, but more produced
• from U-238
• - produces more Pu-239 than it uses

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Nuclear Energy

• Nuclear fusion reactors

• Combine atoms of hydrogen isotopes
• - deuterium, tritium

• Requires high temperature
• - 100 million C
• - experimental
• - uncontrolled fusion - hydrogen bomb

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Problems with Nuclear Power

• Safety

• Disposal of radioactive wastes

• Use of fuel for weapons

• Reduced growth in demand for electricity

• High construction, operating costs

• Funding

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Safety Concerns

• Radiation concerns

• Susceptible tissues reproductive organs, bone
  marrow, digestive tract, spleen, lymph glands,
  fetuses

• Rem - unit of radiation exposure
• - 10 rems low level, few effects
• - 100 rems sterility, no short-term deaths
• - 1000 rems death in days

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Annual Radiation Exposure

• Average 230 mrem (0.230 rem)

• 130 mrem from natural sources
• 100 mrem from human activities
• - 0.1 mrem from nuclear reactors

• Lifespan reduced by 1 minute

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Big Fears

• Core meltdown
• - Chernobyl 86

• Containment shell rupture

• Both have potential for releasing huge amounts of
  radiation

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Disposal of Radioactive Wastes
Nuclear fuel cycle
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Disposal of Radioactive Wastes

• No long-term storage facility
• - protected for 10,000 years
• - radiation declines to low levels

• Most wastes stored on-site

• Site under development
• - Yucca Mountain in Nevada

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Yucca Mountain
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Temporary Storage