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ENERGY RESOURCES. Conventional Energy Alternatives. Nuclear Energy. Provides 15% of energy needs France 77% US 20% (Vermont 85%) – most installed capacity US has never had an accident at a plant where significant amounts of radiation were released

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energy resources

ENERGY RESOURCES

Conventional Energy Alternatives

nuclear energy
Nuclear Energy
  • Provides 15% of energy needs
    • France 77%
    • US 20% (Vermont 85%) – most installed capacity
  • US has never had an accident at a plant where significant amounts of radiation were released
  • No new plants built since 1977 (fear of radioactive release, waste disposal, terrorism)
  • Twice as expensive as coal energy
  • 436 reactors worldwide
  • 103 reactors in 31 states
  • 1973 – 83 billion kWh
  • 2005 –2.6 trillion kWh (4 trillion by 2030)
uranium
Uranium
  • Commonly found in uraninite (pitchblende) from volcanic rocks (nonrenewable)
    • US 22% of known reserves
    • Australia 26%
  • 3 isotopes of uranium:
    • 238U (99.28%), 235U (0.71%) & 234U (<0.01%)
  • Nuclear energy comes from 238U enriched with 3% 235U
fission fusion
Fission & Fusion
  • Fission – splitting of uranium, plutonium or thorium
  • Fusion – merging 2 smaller atoms into one larger atom
nuclear reactors
Nuclear Reactors
  • Contain a core with large number of fuel rods loaded with uranium oxide pellets
    • Fuel pellets 1 cm x 1.5 cm arranged in zirconium alloy tube 12 to 16 feet long called fuel rods
    • Each pellet is equivalent to one ton of coal or 4 barrels of crude oil
    • Rods bundled into clusters of 100-200 called fuel assemblies
    • Small reactors may have 250 assemblies, large up to 3000
nuclear reactors1
Nuclear Reactors
  • Unstable uranium struck with neutron, splits releasing energy & more neutrons
  • Neutrons strike other uranium atoms, initiating a chain reaction
  • Enrichment ensure that there is enough fissionable uranium to maintain the reaction
  • In order to target 235U moderators are used to slow neutrons
    • graphite, beryllium, H2O, D2O
  • Control rods regulate reaction rates
    • cadmium, boron absorb neutrons
light water reactors
Light Water Reactors
  • Use light water H2O as the moderator & coolant
    • Pressurized Water Reactor (PWR)
      • primary water circuit under pressure & cannot boil
      • Piped to 2nd water circuit that can boil, creating steam to spin a turbine to create electricity
      • 3rd water circuit cools 2nd water to be used again
light water reactors1
Light Water Reactors
  • Use light water H2O as the moderator & coolant
    • Boiling Water Reactor (BWR)
      • Water in primary circuit boils to spin the turbine to generate electricity
      • Steam returned to liquid state in a condenser cooled by secondary water circuit
light water reactors2
Light Water Reactors
  • Reactor vessel & steam generator contained in a stainless steel reactor vessel (30 cm thick) and a concrete containment building (at least 1 m thick)
  • Air above nuclear reactors no-fly zones
breeder reactors
Breeder Reactors
  • Create fuel & produce more energy that they use
  • Create fissionable plutonium & thorium
  • Many safety concerns
    • Liquid coolant is sodium metal – very unstable
    • Plutonium could be used in weapons
accidents
Accidents
  • Three Mile Island, PA
    • 3/28/79
    • Reactor lost cooling water and overheated
    • Some fuel rods melted & ruptured
    • Radioactive gases released to atmosphere
    • Residents within 1 mile evacuated
    • No injuries
accidents1
Accidents
  • Price-Anderson Act (1957)
    • designed to ensure that adequate funds would be available to satisfy liability claims of members of the public for personal injury and property damage in the event of a nuclear accident involving a commercial nuclear power plant
    • Does not apply to military facilities
accidents2
Accidents
  • Chernobyl, Ukraine
    • 4/26/86
    • 31 plant workers died that day
    • Nearly 200 staff & responding personnel died from radiation poisoning within 3 weeks
    • Plant did not have concrete containment dome
    • Experienced loss of coolant, roof blown off, radioactive gases released, graphite fire
    • Russians dumped 5,000 tons of lead, sand, clay to bring temperature down
accidents3
Accidents
  • Chernobyl, Ukraine
    • Early cover-up because of politics, Swedish scientists detected radioactive cloud
    • Results
      • 116,000 relocated immediately
      • 350,000 relocated later
      • Increased birth defects
      • 4,000 cases of thyroid cancer in children
    • Radiation has returned to baseline levels in most areas
slide16
Atmospheric currents carried radioactive fallout from Chernobyl across much of the Northern Hemisphere
accidents4
Accidents
  • The China Syndrome
    • Hypothetical concept that if nuclear core temperature escalated out of control (meltdown), the core could melt through the Earth all the way to the other side of the world (China)
radioactivity
Radioactivity
  • Marie Curie coined the term in 1898
  • Radioactive particles
    • Alpha () – electrically negative
    • Beta () – electrically positive
  • Radioactivity considered a bad side effect of nuclear energy
  • Radioactive decay - degrading into lower-energy elements until a stable form is attained
    • Releases ,  and  (gamma) particles from the nucleus
radioactivity1
Radioactivity
  • All radioactive isotopes have a half-life
    • The time it take for one-half of the isotope to decay
    • Plutonium – 239P is 2.13 x 1o6 years
    • Uranium – 238U is 4.5 x 109 years
      • Earth is only 4.6 x 109 years old
radioactive waste storage
Radioactive Waste Storage
  • Until 1970s wastes dumped in ocean
  • Storage has now become a problem
    • 1982 – Nuclear Waste Policy Act – specified federal government responsible for developing a permanent site for highly contaminated radioactive wastes
    • 1987 amendment identified Yucca Mountain (100 miles form Las Vegas)
      • Desert location, eliminates precipitation
      • Specific designed containers guaranteed to last 10,000 years (opponents predict 5000 years)
transporting waste
Transporting Waste
  • Waste must be transported for the East
  • Accident in the middle of a large city dangerous
  • Terrorist attacks
  • Many feel that waste much safer in ponds next to the plants
  • BUT nuclear facilities are running out of radioactive waste storage capacity
biomass
Biomass
  • Energy stored by plants released when burned
  • 40% of world population uses wood or charcoal
  • Biomass and biofuels produced from corn & other crops, wood & paper waste
biomass can be overharvested
Biomass can be overharvested
  • Biomass is only renewable when it is not overharvested
    • With rapid deforestation, soil erosion, and forest failures to regrow, biomass is not replenished
  • As developing nations industrialize, fossil fuels are replacing traditional energy sources
  • Biomass use is growing more slowly than overall energy use
new biomass strategies
New biomass strategies
  • Biomass sources include a variety of materials
  • Biopower = produced when biomass sources are burned in power plants, generating heat and electricity
  • Biofuels = biomass sources converted into fuels to power automobiles
biomass1
Biomass
  • Ethanol – anaerobic digestion of high sugar content plants
  • Great performance in engines
  • Low hydrocarbon & toxic emissions
  • Currently more expensive
  • Disadvantage – enhances pollution effects of compounds like benzene
    • Slows down breakdown in soil & groundwater
cars can run on ethanol
Cars can run on ethanol
  • Flexible fuel vehicles = run on 85% ethanol
    • But, very few gas stations offer this fuel
  • Researchers are refining techniques to produce ethanol from cellulose, so ethanol could be made from low-value crops, instead of high-value crops
biomass2
Biomass
  • Methanol – high-performance liquid fuel (wood alcohol)
  • Low toxic & ozone-forming compounds
  • Costs about the same as gasoline to make
    • M85 – 85% methanol, 15% gasoline
    • M100 – greater air quality & efficiency
      • Superior performance & fire safety
biodiesel produced from vegetable oil
Biodiesel -produced from vegetable oil
  • U.S. biodiesel producers use soybean oil
    • Animal fats, used grease, and cooking oil can also be used
    • Vehicles can run on 100% biodiesel, but the engine needs to be modified
    • Biodiesel cuts down on emissions; its fuel economy is almost as good and costs slightly more than gasoline
biopower generates electricity
Biopower generates electricity
  • Many sources of biomass can be used
    • Waste products of existing industries or processes
    • Woody debris from logging operations and sawmills
    • Crops can be specifically grown, such as fast-growing willow trees or bamboo
    • Co-firing combines biomass with coal
    • Bacterial breakdown of waste to produce methane
biomass energy brings benefits
Biomass energy brings benefits
  • It is essentially carbon-neutral, releasing no net carbon into the atmosphere
    • Only if biomass sources are not overharvested
    • Capturing landfill gases reduces methane emissions
  • Economic benefits include
    • Supporting rural communities
    • Reducing dependence of fossil fuel imports
    • Improved energy efficiency
    • Reduces air pollutants such as sulfur dioxide
drawbacks of biomass energy
Drawbacks of biomass energy
  • Health hazards from indoor air pollution
  • Rapid harvesting can lead to deforestation
  • Growing crops exerts tremendous impacts on ecosystems
    • Fertilizers and pesticides
    • Land is converted to agriculture
  • Biofuel is competing with food production
  • Substantial inputs of energy are required
methane hydrates
Methane Hydrates
  • Methane frozen within ice
  • On continental shelf
  • Melt ice & capture methane
  • If ice caps melt methane released to atmosphere increasing global warming
  • Bermuda Triangle
alternative energies
Alternative Energies
  • Hydroelectric Power
    • Energy created by flowing water
    • Types
      • Impoundment – water held in reservoir
      • Diversion or Run-of-River – water channeled through canal NO DAM NEEDED
hydroelectric power
Hydroelectric power
  • Hydroelectric power = uses the kinetic energy of moving water to turn turbines and generate electricity
  • Storage technique = impoundments harness energy by storing water in reservoirs behind dams
    • Water passing through the dam turns turbines
  • Run-of-river approaches generates energy without greatly disrupting the flow of river water
hydroelectric power is widely used
Hydroelectric power is widely used
  • Hydropower accounts for 2.2% of the world’s energy supply
    • And 16% of the world’s electricity production
  • Nations with large rivers and economic resources have used dams
    • However, many countries have dammed their large rivers
    • People want some rivers left undammed
hydropower is clean and renewable
Hydropower is clean and renewable
  • Hydropower has two clear advantages over fossil fuels for producing electricity:
    • It is renewable: as long as precipitation fills rivers we can use water to turn turbines
    • It is clean: no carbon dioxide is emitted
  • Hydropower is efficient
    • 10:1 EROI (Energy Return on Investment), as high as any modern-day energy source
hydropower has negative impacts
Hydropower has negative impacts
  • Damming rivers destroys habitats
    • Upstream areas are submerged
    • Downstream areas are starved of water
  • Natural flooding cycles are disrupted
  • Thermal pollution of downstream water
  • Periodic flushes of cold reservoir water can kill fish
  • Dams block passage of fish, fragmenting the river and reducing biodiversity
hydropower may not expand much more
Hydropower may not expand much more
  • China’s Three Gorges Dam is the world’s largest dam
  • Most of the world’s large rivers have already been dammed
  • People have grown aware of the ecological impact of dams
  • Developing nations will probably increase hydropower if they have rivers
three gorges dam
Three Gorges Dam
  • Three Gorges Dam Project
conclusion
Conclusion
  • With limited fossil fuel supplies, nations are trying to diversify their energy portfolios
  • Nuclear power showed promise, but high costs and public fears stalled its growth
  • Biomass energy sources include traditional wood and newer biofuels
  • Methane hydrates are potentially a huge reservoir, but uncontrolled release may result in environmental disaster
  • Hydropower is a renewable, pollution-free alternative, but it can involve substantial ecological impacts