1 / 90

Environmental Science

Environmental Science. Unit 7 – Energy (STE 7th ed. Chapter ##). In the long run, humanity has no choice but to rely on renewable energy. No matter how abundant they seem today, eventually coal & uranium will run out. ––Daniel Deudney & Christopher Flavin. Where are we going?.

meghan-marshall
Download Presentation

Environmental Science

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Environmental Science • Unit 7 – Energy(STE 7th ed. Chapter ##)

  2. In the long run, humanity has no choice but to rely on renewable energy. No matter how abundant they seem today, eventually coal & uranium will run out. ––Daniel Deudney & Christopher Flavin

  3. Where are we going? 1. Energy Resources sources, evaluation 2. Oil what is it? supplies, environmental issues 3. Natural Gas what is it? supplies, environmental issues 4. Coal what is it? supplies, environmental issues 5. Nuclear Energy what happened to nuclear power? 6. Renewable Energy what is it? supplies, environmental issues

  4. 1. Energy Resources U.S. has 4.6% of world population uses 24% of the world’s commercial energy

  5. Changes in US Energy Use

  6. Changes in US Energy Use Experience shows that it takes ~50 years to phase in new energy alternatives

  7. Questions • what was the basis of the energy economy until 1800? • what was the basis of the energy economy during 1900? • what was the basis of the energy economy during 1960? • what is the projected basis of the energy economy by the year 2025? • what is the projected basis of the energy economy by the year 2100?

  8. How to Evaluate Resources • How much available? • Oil will be depleted in 40-80 years • Net energy yield? • Cost to develop, phase in, & use? • Environmental effects of extraction, transport, & use? • Water, air and soil pollution • Land disruption • Global Warming • Sustainability? • General concensus is to improve energy efficiency

  9. Net Energy • Suppose that for every 10 units of oil, we have to use and waste 8 units to find, extract, process and transport the oil to users. There are only 2 of useful energy available. • Net Energy = Useful energy produced / Energy used to produce it • 10/8 = 1.25 • The higher the ratio, the higher the net yield OIL • Currently oil has a high net energy ratio since much of it comes from large accessible deposits in the middle east • when the sources deplete the ratio will decrease

  10. Net Energy has a low ratio, large amounts of energy are needed to extract and process uranium ore and to build and operate power plants Ratios < 1 = energy loss

  11. Questions • what are the noticeable patterns? • how will these current patterns change based on future trends predicted? • what is the primary difference between Solar heating and carbon based fuels?

  12. 2. Oil • fossil fuel, produced by the decomposition of deeply buried organic matter from plants & animals – ‘biogenic theory’ • crude oil: complex liquid mixture of hydrocarbons, with small amounts of S, O, N impurities • Only 35-50% can be economically recovered from a deposit. • As prices rise, about 10-25% more can be recovered from expensive secondary extraction techniques • This lowers the net energy yield

  13. Oil: Extraction and Processing • Extraction: • primary - drill & pump • secondary - inject H2O • tertiary - inject steam or CO2 • refine to separate by boiling point: • high: gasoline, aviation fuel • medium: heating oil, diesel • low: grease, wax, asphalt • transport by tanker, truck, pipeline

  14. Oil: Sources • Organization of Petroleum Exporting Countries (OPEC) - 13 countries have most of the world reserves: • Algeria, Ecuador, Gabon, Indonesia, Iran, Iraq, Kuwait, Libya, Nigeria, Qatar, Saudi Arabia, United Arab Emirates, & Venezuela • other important producers: Alaska, Siberia, & Mexico

  15. Oil in US • < 3% of world reserves • uses nearly 30% of world reserves; • 65% for transportation; • increasing dependence on imports

  16. Energy: A Definition 1979 Iranian Revolution Oil Prices 1973 Oil embargo 2003 Iraq Invasion 1939-1945 WW2 9/11 1993 Gulf War

  17. Oil • 1968 – largest oil field in US discovered on Alaska’s North slope (Prudhole Bay) • 10-20 x109 barrels • Difficult to move oil tankers from Atlantic ocean through NW passage • 1977 - Trans-Alaska pipeline to nearest ice-free sea port • Production is decreasing • Look to Arctic National Wildlife Reserve’s 1002 area (ANWR)

  18. Oil: Pros and Cons • Pros • still cheap • Cons • pollution & environmental degradation – GH gases

  19. CO2 Emissions Cleaner burning FF CO2 emissions per unit of energy produced for various energy resources.

  20. 3. Natural Gas • fossil fuel • mixture of 50–90% methane (CH4), smaller amounts of ethane (C2H6), propane (C3H8), & butane (C4H10), and hydrogen sulfide (H2S) • propane & butane removed as liquefied petroleum gas (LPG); • typically transported by pipelines • much burned or pumped back into ground

  21. NG: Sources • Russia & Kazakhstan: almost 40% world's supply • Iran (15%), Qatar (5%), Saudi Arabia (4%), Algeria (4%), United States (3%), Nigeria (3%), Venezuela (3%) • Natural gas is versatile and clean-burning fuel, but it releases the greenhouse gases carbon dioxide (when burned) and methane (from leaks) into the troposphere

  22. NG: Pros and Cons • Pros • reserves 65–80 yrs for U.S., 125 years for world at current consumption rates; • burns cleaner, & produces less carbon dioxide than other fossil fuels • Cons • pollution & environmental degradation

  23. 4. Coal Coal is a solid fossil fuel that is formed in several stages as the buried remains of land plants that lived 300-400 million years ago

  24. Coal: Sources Due to air pollution laws, search for cleaner coal, thicker seams • Coal reserves in the United States, Russia, and China could last hundreds to over a thousand years • The U.S. has 27% of the world’s proven coal reserves, followed by Russia (17%), and China (13%) • In 2005, China and the U.S. accounted for 53% of the global coal consumption Since 1940’s production shifted west, from underground to surface mines

  25. Coal • Coal seams vary in thickness from a few inches to hundreds of feet • 60% coal produced by strip mining – ripping tops off mountains Aerial view of a Montana strip mine. Dragline used in strip mine to remove coal.

  26. The Washington Post 032008

  27. Coal: Pros and Cons • Pros • most abundant fossil fuel; • high net energy yield; • Cons • dirtiest fuel, highest carbon dioxide • major environmental degradation • major threat to health

  28. 5. Nuclear Energy • Nuclear fission is the splitting of a large nucleus into smaller nuclei • Energy is released because the sum of the masses of these fragments is less than the original mass • Heat produced drives a turbine to produce electricity

  29. Power from Nuclear FissionCritical Mass • Self-propagating chain reaction • Excess neutrons • With small mass, 10n are lost • Past 15 kg, reaction is sustained http://www.kscience.co.uk/animations/chain_reaction.swf

  30. Power from Nuclear FissionTypes of Fission Reactor • Commerical nuclear power is produced using thermal neutrons Fuel rods contain fissile material (natural, enriched, or mixed) Moderator slows down neutrons, increases chances of fission Control rods made from boron absorb 10n Coolant water or gas Steam turbine or generator converts heat into electricity • Different reactors use different coolants, fuel and moderators

  31. Small amounts of radioactive gases Uranium fuel input (reactor core) Control rods Containment shell Heat exchanger Turbine Steam Generator Electric power Waste heat Hot coolant Useful energy 25%–30% Hot water output Pump Pump Coolant Pump Pump Waste heat Cool water input Moderator Coolant passage Pressure vessel Shielding Water Condenser Periodic removal and storage of radioactive wastes and spent fuel assemblies Periodic removal and storage of radioactive liquid wastes Water source (river, lake, ocean)

  32. Power from Nuclear Fission Types of Fission Reactor: PWR Water remains liquid due to high pressure Expansion of water as T rises reduces number of slow moving n Water = coolant, moderator and n absorber Popular design due to safety record, more economic to run

  33. After three or four years in a reactor, spent fuel rods are removed and stored in a deep pool of water contained in a steel-lined concrete container After spent fuel rods are cooled, they are moved to dry-storage containers made of steel or concrete

  34. Decommissioning of reactor Fuel assemblies Reactor Enrichment of UF6 Fuel fabrication (conversion of enriched UF6 to UO2 and fabrication of fuel assemblies) Temporary storage of spent fuel assemblies underwater or in dry casks Conversion of U3O8 to UF6 Uranium-235 as UF6Plutonium-239 as PuO2 Spent fuel reprocessing Low-level radiation with long half-life Geologic disposal of moderate & high-level radioactive wastes Open fuel cycle today “Closed” end fuel cycle

  35. What Happened to Nuclear Power? • After more than 50 years of development and enormous government subsidies, nuclear power has not lived up to its promise because: • Multi billion-dollar construction costs. • Higher operation costs and more malfunctions than expected. • Poor management. • Public concerns about safety and stricter government safety regulations • some countries (France, Japan) investing increasingly • U.S. currently ~7% of energy nuclear; • no new U.S. power plants ordered since 1978; 40% of 105 commercial nuclear power expected to be retired by 2015 & all by 2030; • France 78% energy nuclear

  36. TMI • March 29, 1979, number 2 reactor near Harrisburg, Pennsylvania lost coolant & core suffered partial meltdown • Majority contained • 50,000 people evacuated & another 50,000 fled area; • unknown amounts of radioactive materials released • partial cleanup & damages cost $1.2 billion so far • released radiation increased cancer rates

  37. Movie CNN 2002

  38. Chernobyl • April 26, 1986, reactor explosion (Ukraine) flung radioactive debris into atmosphere • Flawed design • Major world-wide release of radioisotopes due to no secondary containment • 56 immediate + 4000 expected deaths • Encased in concrete

  39. Movie CNN 2002

  40. Nuclear: Pros and Cons • Pros • U.S. has major reserves of uranium • Cons • risk of radioactive contaminant leaks • radioactive wastes (short– & long–term)

  41. A 1,000 megawatt nuclear plant is refueled once a year, whereas a coal plant requires 80 rail cars a day

  42. Nuclear Waste Solutions • Scientists disagree about the best methods for long-term storage of high-level radioactive waste: • Bury it deep underground. • Shoot it into space. • Bury it in the Antarctic ice sheet. • Bury it in the deep-ocean floor that is geologically stable. • Change it into harmless or less harmful isotopes.

  43. What’s next? • General consensus? • To improve energy efficiency • Disagreement about the next best option Option 1 – turn to renewable energy resources Option 2 – burn more coal Option 3 – turn to natural gas (cleaner) Option 4 – Nuclear power

  44. 6. Renewables 1. Energy efficiency 2. Solar energy 3. Hydropower 4. Wind Power 5. Biomass 6. Solar–hydrogen revolution 7. Geothermal 8. Sustainability

More Related