Evaluating Energy Resources

1. Evaluating Energy Resources • Renewable energy • Non-renewable energy • Future availability • Net energy yield • Cost • Environmental effects

2. Extracting Energy and Mineral Resources • Surface, subsurface mines, wells

3. Removing Nonrenewable Mineral Resources Surface mining Subsurface mining • Overburden

4. Points of View • Cornucopians - we will not run out of non-renewable resources because of economics and technology • Neo-Malthusians - we will run out of non-renewable resources (limited supply) - must control population, conserve

5. Supplemental Energy Solar energy - 99% of all energy used Supplemental energy - everything else

6. History of Supplemental Energyin United States • Wood through mid-1800s • Renewable • Maximum sustained yield limits supply • Coal replaced wood by 1900 • Oil, natural gas exploited (since mid-1900s) #1-oil, #2-natural gas, #3-coal - all non-renewable • Use growing dramatically

7. 100 Wood Coal 80 Natural gas 60 Contribution to total energy consumption (percent) Oil 40 Hydrogen Solar 20 Nuclear 0 1800 1875 1950 2025 2100 Year

8. How long will supplies last? • U.S. (5%) uses 25% of energy • Depends on: - rate of use - discovery of new supplies • Resource supply lifetime - oil - 30-60 years - natural gas - 50-200 years - coal - 65-900 years

9. North American Energy Resources

10. Oil Resources • Petroleum (crude oil) • Primary recovery - 1/3 recoverable • Secondary recovery - heavy oil (10%) • U.S. is major oil importer - thousands of low-output wells • Saudi Arabia - largest known reserves - supply world for 10 years - Alaskan supply - 6 months

11. OPEC • Organization of Petroleum Exporting Countries • Supplies ~30% of U.S. oil imports • #1 Mexico #2 Canada #3 Venezuela (OPEC member)

12. Oil Shale and Tar Sands • Oil shale 3X conventional • Kerogen 25 gallons/ton Energy in=energy out • Tar sands • Bitumen 3X return on energy inputs

13. Natural Gas • 50-90% methane • Propane, butane removed, liquified • Cleanest burning, lowest costs • Problems: leaks, explosions • Unconventional: tight sands - 1-3 X conventional supply, but expensive

14. Coal Carbon (energy content) and sulfur

15. Coal • Bituminous most abundant (52%), but high in sulfur • Anthracite most ideal (high energy, low sulfur), but least abundant (2%) • Subbituminous (38%) moderate energy, moderate pollution potential • Lignite (8%) low energy, low pollution potential

16. Coal • Surface versus subsurface mines

17. North American Energy Resources

18. Coal Mining in United States • Western surface mines • Mostly subbituminous, lignite • Used mostly for generating electricity, steel-making industry • Most used east of Mississippi River • Transportation vs. volume costs, sulfur - slurry pipeline?

19. Burning Coal More Cleanly • Fluidized-Bed Combustion -calcium sulfate used in dry wall

20. Coal Gasification - methane Remove dust, tar, water, sulfur Raw coal Recover sulfur Air or oxygen Raw gases Steam Clean methane gas O2 2CO 2C Coal + Pulverizer Recycle unreacted carbon (char) CO + 3H2 CH4 + H2O Methane (natural gas) Slag removal Pulverized coal

21. Coal Liquefaction - liquid fuels • Both gasification and liquefaction lose 30-40% of energy contained in coal

22. Nuclear Energy • Big question mark in energy industry • Tremendous potential, plagued by safety and cost problems • 3 ways to produce nuclear power 1) conventional nuclear fission reactor 2) breeder nuclear fission reactor 3) nuclear fusion reactor

23. Nuclear Energy • Use radioactive isotopes • Isotopes - different forms of same element - atoms have differing masses - e.g. U-238, U-235 • Radioactive - unstable atoms emit radiation (rays and particles)

24. Nuclear Energy • Conventional fission reactors • Uranium-235 (U-238 common) • Nucleus split by moving neutron - Core, heat exchanger, generator

25. Reactors in the United States

26. Nuclear Energy • Breeder fission reactors • Uses plutonium-239 as fuel U-238 + neutron = Pu-239 • Pu-239 fissioned, but more produced from U-238 - produces more Pu-239 than it uses

27. Nuclear Energy • Nuclear fusion reactors • Combine atoms of hydrogen isotopes - deuterium, tritium • Requires high temperature - 100 million °C - experimental - uncontrolled fusion - hydrogen bomb

28. Problems with Nuclear Power • Safety • Disposal of radioactive wastes • Use of fuel for weapons • Reduced growth in demand for electricity • High construction, operating costs • Funding

29. Safety Concerns • Radiation concerns • Susceptible tissues: reproductive organs, bone marrow, digestive tract, spleen, lymph glands, fetuses • Rem - unit of radiation exposure - 10 rems: low level, few effects - 100 rems: sterility, no short-term deaths - 1000 rems: death in days

30. Annual Radiation Exposure • Average 230 mrem (0.230 rem) • 130 mrem from natural sources • 100 mrem from human activities - 0.1 mrem from nuclear reactors • Lifespan reduced by 1 minute

31. Big Fears • Core meltdown - Chernobyl ‘86 • Containment shell rupture • Both have potential for releasing huge amounts of radiation

32. Disposal of Radioactive Wastes Nuclear fuel cycle

33. Disposal of Radioactive Wastes • No long-term storage facility - protected for 10,000 years - radiation declines to low levels • Most wastes stored on-site • Site under development - Yucca Mountain in Nevada

34. Yucca Mountain

35. Temporary Storage