Energy lecture 7


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NAU Environmental Science Lecture 7 Energy

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Energy lecture 7

  1. 1. Environmental Science A Study of Interrelationships Thirteenth Edition Enger & Smith Chapter 9 Non-Renewable Energy Sources Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
  2. 2. Non-Renewable Energy Sources
  3. 3. 9.1 Major Energy Sources  Nonrenewable energy sources • resources are being used faster than can be replenished. – Coal, oil, and natural gas  Renewable energy sources • replenish themselves • feature of the environment. – Solar, geothermal, tidal, etc. – 12% of the energy used worldwide – hydroelectricity and firewood
  4. 4. 9.3 Fossil-Fuel Formation  Coal • 300 million years ago, • plant material—underwater--decay • forming a spongy mass of organic material. • Due to geological changes – deposits were covered by seas – covered with sediment. • Pressure and heat over time – transformed the organic matter into coal.
  5. 5. 9.3 Fossil-Fuel Formation Recoverable coal reserves of the world 2004
  6. 6. 9.3 Fossil-Fuel Formation  Oil and natural gas • microscopic marine organisms • accumulated on the ocean floor • covered by sediments. • Muddy sediment formed shale – contained dispersed oil. • Natural gas often forms on top of oil – Due to higher temps
  7. 7. 9.3 Fossil-Fuel Formation Crude oil and natural gas pool
  8. 8. 9.4 Issues Related to the Use of Fossil Fuels  Fossil fuels supply 80% of world’s commercial energy.  Coal is most abundant fossil fuel. • Only 30% of world energy is from coal • Primarily used for generating electricity.
  9. 9. 9.4 Issues Related to the Use of Fossil Fuels  Extraction methods: • Surface mining (strip mining), – removing material on top of a vein – efficient but destructive • Underground mining – Minimizes surface disturbance, but is costly and dangerous.
  10. 10. 9.4 Issues Related to the Use of Fossil Fuels Underground mining
  11. 11. 9.4 Issues Related to the Use of Fossil Fuels • Health and Safety Issues – 2000-2010, 60 deaths per year – Many miners suffer from black lung disease – a respiratory condition – results from the accumulation of fine coal-dust particles in the miners’ lungs.
  12. 12. 9.4 Issues Related to the Use of Fossil Fuels  Transportation Issues • Coal is bulky • Use railroad  Landscape Disturbance • Mountain top removal • Minimize disturbance – Reclaiming area – Mining companies do little to lower their costs
  13. 13. 9.4 Issues Related to the Use of Fossil Fuels Surface-mine reclamation
  14. 14. Subsidence Underground Mining Subsidence-sinking of land
  15. 15. 9.4 Issues Related to the Use of Fossil Fuels  Environmental Issues • Burning coal releases pollutants – (carbon and sulfur). – Released into atmosphere annually. • Sulfur leads to acid mine drainage and acid deposition.
  16. 16. 9.4 Issues Related to the Use of Fossil Fuels Acid mine drainage
  17. 17. 9.4 Issues Related to the Use of Fossil Fuels • Air Pollution – Mining creates dust pollution – Mercury is released into the air when coal is burned. • Increased amounts of atmospheric carbon dioxide are implicated in global warming.
  18. 18. 9.4 Issues Related to the Use of Fossil Fuels  Oil (35% world energy) • more concentrated than coal • burns cleaner • transported through pipelines • Ideal for automobile use. • Difficult to find. • Causes less environmental damage than coal mining.
  19. 19. 9.4 Issues Related to the Use of Fossil Fuels  Source of oil--located  extracted and transported to the surface  Primary Recovery methods • Water/gas pressure is great (with oil) – oil is forced to the surface---when well is drilled • Water/gas pressure is low – oil pumped to the surface • 5–30% (primary)
  20. 20. 9.4 Issues Related to the Use of Fossil Fuels Offshore drilling
  21. 21. 9.4 Issues Related to the Use of Fossil Fuels  Secondary Recovery • Water or gas is pumped into a well • drive the oil out of the pores in the rock • 40% of the oil---extracted.
  22. 22. 9.4 Issues Related to the Use of Fossil Fuels  Processing • From the ground, oil is not in a form suitable for use – must be refined. – Separate components by – Heat oil in distillation tower • Multiple products can be produced from a single barrel of crude oil. – Plastics, rubber, etc
  23. 23. 9.4 Issues Related to the Use of Fossil Fuels Processing crude oil
  24. 24. 9.4 Issues Related to the Use of Fossil Fuels  Oil Spills • Accidental spills – about 1/3 of oil pollution resulting from shipping. 2010 Deepwater Horizon: 10,000 tons of oil largest spill
  25. 25. Discussion  /  Eminent Domain • The power to take private property for public use by a state, municipality, or private person or corporation (authorized to exercise functions of public character) • following the payment of just compensation to the owner of that property
  26. 26. Keystone XL pipeline route
  27. 27. 9.4 Issues Related to the Use of Fossil Fuels  Natural gas • Drilling operations similar to oil.  Hard to transport • burned off at oil fields (waste product) • New transportation methods – Liquefaction at -126o F – Tankers transport liquefied natural gas • Unloading/loading facilities – located off shore (explosions)
  28. 28. 9.4 Issues Related to the Use of Fossil Fuels  Least disruptive to environment Air Pollution minimal Fracking
  29. 29. 9.5 Nuclear Power  Nuclear power • Not a fossil fuel • fueled by uranium – obtained from mining and is non-renewable. – 5th most important energy  Does not produce CO2  Less costly than oil/natural gas • For electricity (developing nations)
  30. 30. 9.5 Nuclear Power  As of 2011 • 440 nuclear power reactors in operation and • 61 plants under construction in 13 countries.
  31. 31. 104 Nuclear Power Plants in U.S.
  32. 32. 9.6 The Nature of Nuclear Energy  The nuclei of certain atoms • unstable and spontaneously decompose • isotopes are radioactive.  Neutrons, electrons, protons, other particles • released during nuclear disintegration • great deal of energy
  33. 33. Atomic Structure Isotopes of hydrogen
  34. 34. 9.6 The Nature of Nuclear Energy  Nuclear disintegration (releases energy) • from the nucleus as radiation • three major types – Differ by size and how fast it travels  Radioactive half-life • time it takes for half the radioactive material to spontaneously decompose.
  35. 35. 9.7 Nuclear Chain Reaction  Nuclei • Release radiation • And Neutrons  Nuclear fission occurs when neutrons impact and split the nuclei of certain other atoms. • Split (Fission)
  36. 36. Nuclear Chain Reaction  splitting nuclei release neutrons,  which themselves strike more nuclei,  in turn releasing even more neutrons.
  37. 37. 9.8 Nuclear Fission Reactors  A nuclear reactor is a device that permits a controlled fission chain reaction. • Nucleus of Uranium-235 atom struck by a slowly moving neutron • the nucleus splits into smaller particles • Causes rapidly-moving neutrons to be released – which strike more atoms. • continues to release energy – until the fuel is spent (Uranium-235) – or the neutrons are prevented from striking other nuclei.
  38. 38. Nuclear chain reaction  Need • • • • The fuel (uranium-235) A moderator Control Rods Core coolant
  39. 39. 9.8 Nuclear Fission Reactors  Control rods • lowered into the reactor to absorb neutrons • and control the rate of fission. • When withdrawn, the rate of fission increases.  Moderator • • • • substance that absorbs energy, which slows neutrons, enabling them to split the nuclei of other atoms more effectively. Water  Coolant---usually water
  40. 40. 9.8 Nuclear Fission Reactors Pressurized water-reactor  Nuclear reactor • • • • Produces heat Water to steam Turns turbine Generate Electricity
  41. 41. 9.10 Issues Related to the Use of Nuclear Fuels  Concerns about the use of nuclear fuels • danger associated with radiation • radiation interact with atoms, ions are formed – ionizing radiation – Ionizing radiation affects DNA and can cause mutations. – Cancer – Large doses of radiation are clearly lethal.
  42. 42. The Biological Effects of Ionizing Radiation  Time, distance, and shielding are the basic principles of radiation protection. • Water, lead, and concrete are common materials used for shielding
  43. 43. Three Mile Island Pennsylvania 1979 Partial core meltdown Pump and valve malfunction Radioactive steam into atmosphere
  44. 44. Reactor Safety  Chernobyl is a small city in Ukraine, north of Kiev.  It is the site of the world’s largest nuclear accident, which occurred April 26, 1986. • Experiments were being conducted on reactor. • Operators violated six important safety rules. • Shut off all automatic warning systems, automatic shutdown systems, and the emergency core cooling system for the reactor.
  45. 45. Reactor Safety  In 4.5 seconds, the energy level of the reactor increased 2000 times.  The cooling water converted to steam and blew the 1102-ton concrete roof from the reactor.  The reactor core caught fire.  It took 10 days to bring the burning reactor under control. • There were 37 deaths; 500 people hospitalized (237 with acute radiation sickness); 116,000 people evacuated.
  46. 46. Reactor Safety The accident at Chernobyl
  47. 47. Reactor Safety  The Fukushima nuclear power plant was damaged on March 11, 2011 following a magnitude 9 earthquake and tsunami. • Heat exchangers were damaged, power to the site was cut off – diesel generators designed to provide power in an emergency were flooded and stopped operating. • Explosions, fires, and leaks in the cooling system released radiation into the atmosphere and sea water.
  48. 48. Other issues  Terrorism • radiological dispersal devices (RDDs), or dirty bombs. • They cause panic, not numerous deaths.  Waste • All of the processes involved in the nuclear fuel cycle have the potential to generate waste.  Transport of radioactive materials.  Possibility of an accident or mishandling that could release radioactive material.
  49. 49. Decommissioning Nuclear Power Plants  The life expectancy of most electrical generating plants (fossil fuel or nuclear) is 30-40 years.  Nuclear plants are decommissioned, not demolished.  2-step process. • Stage 1 removing, properly disposing of, or storing – fuel rods and water used in the reactor. • Stage 2 Secure the plant to allow radioactive materials with a short half-life to disintegrate and then dismantle the plant.
  50. 50. Nuclear Plant  Nuclear plant in Nebraska (Fort Calhoun)  20 miles north of Omaha •
  51. 51. Summary  Resources are naturally occurring substances of use to humans.  Reserves are known deposits from which materials can be extracted profitably with existing technology under present economic conditions.  Coal is the world’s most abundant fossil fuel.  The supply of oil, like all fossil fuels, is limited.  Natural gas is another major source of fossil-fuel energy, but transport of natural gas to consumers is problematic.
  52. 52. Summary  Nuclear fission is the splitting of the nucleus of an atom.  All reactors contain a core with fuel, a moderator to control the rate of the reaction, and a cooling mechanism to prevent the reactor from overheating.
  53. 53. Summary  The nuclear fuel cycle involves mining and enriching the original uranium ore, fabricating it into fuel rods, using the fuel in reactors, and reprocessing or storing the spent fuel rods.  Fuel and wastes must also be transported.  Each step in the process presents a danger of exposure.
  54. 54. Summary  Although accidents at Three Mile Island and Chernobyl raised safety concerns for a time, rising energy prices have stimulated increased building of nuclear power plants in many countries.  Disposal of waste is expensive and controversial. • Long-term storage in geologically stable regions is supported. • Russia, Japan, and the UK operate nuclear reprocessing facilities to reduce future long-term storage needs.