Energy
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Transcript of Energy
Chapter 17
Energy
Steamgenerator
Waterpumps
Crane formoving fuel rods
TurbinesTurbines
ReactorReactor
Coolingpond
Coolingpond
5 Reactor power output was lowered too much, making it too difficult to control.
4 Additional water pump to cool reactor was turned on. But with low power output and extra drain on system, water didn’t actually reach reactor.
3 Automatic safety devices that shut down the reactor when water and steam levels fall below normal and turbine stops were shut off because engineers didn’t want systems to “spoil” experiment.
Radiation shieldsRadiation shields
2 Almost all control rods were removed from the core during experiment.
1 Emergency cooling system was turned off to conduct an experiment.
Figure 17-1Page 350
Effects: Blew roof off reactor building Clouds of radioactive material Premature deaths Radioactive crops, cattle Thyroid cancer
Chernobyl
99% of energy comes from the sun
Other 1% comes from commercial energy (nonrenewable)
Commercial energy- burning of fossil fuels 84% nonrenewable 16% renewable
Energy Sources
Figure 17-3aPage 352
World
Nuclear power6%
Hydropower, geothermal,solar, wind
6%
NaturalGas22%
Biomass10%
Oil33%
Coal23%
Figure 17-3bPage 352
United States
Nuclear power8% Hydropower
geothermalsolar, wind
3%
Biomass3%
NaturalGas24%
Oil39%
Coal23%
Would take at least 50 years (+ huge financial investments) to phase in new energy alternatives
New Energy Alternatives
How much of energy resource is available in near & long-term future?
Net energy yield? Cost for development, phase in, & use? Government research & development
subsidies & tax breaks? How will dependence affect national & global
economic & military security? Vulnerable to terrorism? How will extraction, transportation, & use
affect environment, human health, & climate?
7 Questions Concerning New Energy
Total amount of energy available from resource minus energy needed to find, extract, process, & get resource to consumers
Importance- higher net energy ratios make better energy sources
Oil- high ratio- comes from large, accessible, & cheap-to-extract deposits
Nuclear power- low ratio- requires large amounts of energy input
Net Energy
Petroleum (crude oil)- thick, gooey liquid consisting of combustible hydrocarbons
Extracted- by wells drilled into deposits
Refining- heat & distill (separate by boiling points)
Petroleum
Products of oil distillation
Pesticides Plastics Synthetic fibers Paints Medicines
Petrochemicals
Top 5 reserves- Saudi Arabia, Iraq, United Arab Emirates, Kuwait, Iran
2.9% of oil is found in US reserves 26% of oil is used by US 55% of US oil used is imported
Oil Reserves
Global – 80% depleted within 41-93 years
US – 10-48 years(2005)
Oil Supply
Could increase U.S oil andnatural gas supplies
Could reduce oil importsslightly
Would bring jobs and oilrevenue to Alaska
May lower oil prices slightly
Oil companies havedeveloped Alaskan Oil fields withoutsignificant harm
New drilling techniqueswill leave little environ-mental impact
Figure 17-14Page 360
Trade-OffsDrilling for Oil and Natural Gas
In Alaska’s ArcticNational Wildlife Refuge
Only 19% of finding oil equal to what U.S. consumes in 7-24 months
Too little potential oil to significantlyreduce oil imports
Costs too high and potential oil supply toolittle to lower energy prices
Studies show considerable oil spills andother environmental damage fromAlaskan oil fields
Potential degradation of refuge notworth the risk
Unnecessary if improved slant drillingallows oil to be drilled fromoutside the refuge
Advantages Disadvantages
Ample supply for 42-93 years
Low cost (with huge subsidies)
High net energy yield
Easily transported withinand between countries
Low land use
Technology is welldeveloped
Efficient distribution system
Advantages
Figure 17-15Page 360
Trade-OffsConventional Oil
Disadvantages
Need to find substitute within 50 years
Artifically low price encourages waste and discourages search for alternative
Air pollution when burned
Releases CO2 when burned
Moderate water pollution
Advantages Disadvantages
Moderate cost (oil sand)
Large potential supplies, especially oil sandsin Canada
High cost (oil shale)
Low net energy yield
Large amount of water needed for processing
Severe land disruption from surface mining
Water pollution from mining residues
Air pollution when burned
CO2 emissionswhen burned
Easily transported within and between countries
Efficient distributionsystem in place
Figure 17-18Page 362
Trade-OffsHeavy Oils from
Oil Shale and Oil Sand
Technology is well developed
Natural Gas Underground deposits of gases 50-80% methane (by weight)
Remaining is propane or methane
LPG – liquefied petroleum gas – natural gas mixture of liquefied propane & butane gas
LNG – liquefied natural gas – natural gas converted to liquid by cooling to low temperature
Natural Gas Reserves Russia Iran Qatar
3% of reserves found in US
World supply – should last 62-125 years US supply – 55-80 years
Good fuel for fuel cells and gas turbines
Low land use
Easily transported by pipeline
Moderate environmental impact
Lower CO2 emissions thanother fossil fuels
Less air pollution than other fossil fuels
Low cost (with huge subsidies)
High net energy yield
Ample supplies (125 years)
Sometimes burned off andwasted at wells because of lowprice
Shipped across ocean as highlyexplosive LNG
Methane (a greenhouse gas) can leak from pipelines
Releases CO2 when burned
Nonrenewable resource
Difficult to transfer from one countryto another
Requires pipelines
Figure 17-19Page 363Advantages
Trade-OffsConventional Natural Gas
Disadvantages
Coal Solid, combustible mixture of organic
compounds with 30-98% Carbon by weight
Extraction- underground (subsurface) mining, surface mines
2 major uses- steel production & electricity
Increasing moisture content
Increasing heat and carbon content
Peat(not a coal)
Lignite(brown coal)
Bituminous Coal(soft coal)
Anthracite(hard coal)
Heat
Pressure Pressure Pressure
Heat Heat
Partially decayedplant matter in swampsand bogs; low heatcontent
Low heat content;low sulfur content;limited supplies inmost areas
Extensively usedas a fuel becauseof its high heat contentand large supplies;normally has ahigh sulfur content
Highly desirable fuelbecause of its highheat content andlow sulfur content;supplies are limitedin most areas
Figure 17-20Page 364
Coal Reserves US, Russia, China
25% of reserves are in US
World supply- 300 years US- 300-400 yrs
Low cost (with huge subsidies)
High net energy yield
Ample supplies(225–900 years)
Releases radioactive particles and mercury into air
High CO2 emissions when burned
Severe threat to human health
High land use (including mining)
Severe land disturbance, air pollution, and water pollution
Very high environmental impact
Mining and combustiontechnology well-developed
Air pollution can be reduced with improvedtechnology (but addsto cost)
Figure 17-21Page 365Advantages
Trade-OffsCoal
Disadvantages
Moderate cost (with large government subsidies)
Vehicle fuel
Large potential supply
High water use
Increased surface mining of coal
High environmental impact
Requires mining 50% more coal
Higher cost than coal
Low to moderate net energy yield
Lower air pollution when burned than coal
Figure 17-22Page 365Advantages
Trade-OffsSynthetic Fuels
Disadvantages
High CO2 emissions when burned
Nuclear Fission Reactor Isotopes of Uranium & Plutonium are split
(chain reaction) Heat generated produces steam which
turns turbine = electricity
Light-water Nuclear System (LWR) Fuel- uranium oxide- stable uranium
pellets Control rods- neutron-absorbing material;
regulates fission/power Moderator- slows neutrons to continue
chain rxn (water, graphite) Coolant- water-circulates through core to
remove heat from fuel rods & to produce steam
Containment vessel- thick, strong walls; keeps radioactive material from escaping to environment
Water-filled pools (dry casks)- on-site storage for highly radioactive (spent) fuel rods
Nuclear Fuel Cycle Mining uranium Processing as fuel Use in reactor Safely storing wastes Disposing of reactor
Open Nuclear Fuel Cycle Isotopes are not removed by reprocessing
nuclear wastes Eventually reburied in underground
disposal facility
Closed Nuclear Fuel Cycle Fissionable isotopes (Uranium-235 &
Plutonium-239) are removed from spent fuel assemblies for reuse as nuclear fuel
Must be stored for 10,000 years
Figure 17-24Page 368
Decommissioning of reactor
Reactor
Fuel assemblies
Enrichment UF6
Conversion of U3 O8 to UF6
Fuel fabrication
(conversion of enrichedUF6 to UO2 and fabricationof fuel assemblies)
Uranium 235 asUF6 Plutonium-239as PuO2
Low level radiationwith long half-life
Spent fuelreprocessing
Temporary storageof spent fuel assemblies
underwater or in dry casks
Geologic disposal of moderateand high-level radioactive wastes
Open fuel cycle today
Prospective “closed” end of fuel cycle
Nuclear Power Dev. After WW2 Atomic Energy Commission- promised
lower cost for nuclear energy (vs. coal) Government (taxpayers) paid ¼ cost of
building commercial reactors & guaranteed there would be no cost overruns
After insurance companies refused to insure nuclear power, Congress passed Price-Anderson Act to protect US nuclear industry & utilities from significant liability in accidents
7 Factor of Declined Use of NP Multibillion dollar construction cost
overruns Higher operating costs More malfunctions than expected Poor management Public safety concerns Stricter government safety regulations Investor concerns about economic
feasibility of nuclear power
Low risk of accidents because of multiple safety systems (except in 35 poorly designed and run reactors in former Soviet Unionand Eastern Europe)
Moderate land use
Moderate land disruption and water pollution(without accidents)
Emits 1/6 as much CO2 as coal
Low environmentalimpact (without accidents)
Large fuel supply
Spreads knowledge andtechnology for building nuclear weapons
No widely acceptable solution for long-term storage of radioactive wastes and decommissioning worn-out plants
Catastrophic accidents can happen (Chernobyl)
High environmental impact (with major accidents)
Low net energy yield
High cost (even with large subsidies)
Figure 17-26Page 370
Subject to terrorist attacks
Advantages
Trade-OffsConventional Nuclear Fuel Cycle
Disadvantages
Ample supply
High net energy yield
Very high air pollution
High CO2 emissions
High land disruption fromsurface mining
High land use
Low cost (with huge subsidies)
Ample supply of uranium
Low net energy yield
Low air pollution (mostly from fuel reprocessing)
Low CO2 emissions (mostly from fuel reprocessing)
Much lower land disruption fromsurface mining
Moderate land use
High cost (with hugesubsidies)
Figure 17-27Page 371Coal
Trade-Offs
Coal vs. Nuclear
Nuclear
Safety Features Multiple built-in safety features 15-45% chance of complete core
meltdown in US reactor during the next 20 years
39 US reactors have 80% chance of failure in containment shell from meltdown or explosion
Vulnerable to Terrorist Attack Plants were not designed to withstand an
attack like September 11 Insufficient security against ground-level
attacks
Attack on Stored Radioactive Waste Highly radioactive & thermally hot fuel
would be exposed to air & steam Zirconium outer cover would catch fire Fire would burn for days Release significant amount of radioactive
material into atmosphere Large areas contaminated for decades Economic & psychological havoc
Low-Level Waste Gives off small amounts of ionizing
radiation Must be stored safely for 100-500 years Placed in steel drums & shipped to 2
regional (state or fed run) landfill
Includes: tools, building materials, clothing, glassware, & other contaminated items
High-Level Waste Bury deep underground Shoot into space or sun Bury in Antarctic ice sheet or Greenland
ice cap Dump into subduction zone Bury in mud deposits in ocean basins Change into harmless isotopes
Yucca Mountain Storage Site+Negligible risks of accident or sabotage of waste shipments-Decrease national security-Many shipments of waste material-Geologic instability
Decommissioning of Worn-out Nuclear Power Plants Dismantle plant & store large volume of
highly radioactive materials in high-level nuclear waste storage facility
Physical barrier around plant with full-time security for 30-100 years before dismantling plant
Enclose entire plant in tomb that must last & be monitored for several thousand years
Dirty Radioactive Bombs Explosion & cancers could kill thousands Spread radioactive material over hundreds
of city blocks Contaminate buildings & soil Clean-up would cause billions $$ Intense psychological terror & panic
Conventional Nuclear Power+ Lower operating costs- Must include total cost
Breeder Nuclear Fission+ Generate more nuclear fuel than they consume- Failed safety system could result in loss of liquid sodium coolant = combustion in air & explosion in water- Slow process- Cost
Nuclear Fusion+ No emissions of air pollutants (carbon dioxide)+ Infinite fuel source (water)+ Less radioactive waste+ No risk of meltdown or release of large amounts of radioactive materials+ Little risk of bomb-grade materials+ Used to destroy toxic waste- Negative energy yield- Cost
Government SubsidiesFor the research & development of conventional nuclear power: Conventional nuclear power cannot
compete in today’s open, decentralized, & unregulated energy market
Should keep nuclear options available for future use