ENERGY RESOURCES - PowerPoint PPT Presentation

ENERGY RESOURCES

Conventional Energy Alternatives

• 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 – splitting of uranium, plutonium or thorium
• Fusion – merging 2 smaller atoms into one larger atom

• 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

• 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

• 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

• 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

• 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

• 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

• 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

• 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)

• 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 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

• 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

• 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

• 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

• 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

• 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

• 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 frozen within ice
• On continental shelf
• Melt ice & capture methane
• If ice caps melt methane released to atmosphere increasing global warming
• Bermuda Triangle

• 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 = 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

• 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 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

• 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

• 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 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