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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


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)
  • 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
  • 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
  • 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
  • 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
  • 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
Atmospheric currents carried radioactive fallout from Chernobyl across much of the Northern Hemisphere
  • 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)
  • 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
  • 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
  • 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
  • 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
  • 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
  • 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