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ENERGY!! Ch 10, 11, 12
Developed vs. Developing • 20% of the world’s population lives in highly developed countries in 2000, these people used 60% of the commercial energy consumed worldwide. That means… Each person in highly developed countries uses approximately eight times as much energy as each person in developing countries.
DEVELOPING • Farmers rely on their own physical energy or animal energy. • Goal of Developing Countries: improve the standard of living. • Boost economic development? • Will be followed by a rise in per-capita energy consumption. DEVELOPED • High-energy input • Fertilizers, machinery, pesticides, etc. • Makes the agricultural productivity higher! • Developed nations have a more stable population, so per-capita energy consumption may be close to saturation. Must increase energy efficiency!!!
FOSSIL FUELS • Partially decayed remnants of organisms formed millions of years ago. • NONRENEWABLE!!! • Formation: • COAL: • Swamp plants died and fell into the water, which slowed their decay (little O2) • Layers of sediment piled on top • Pressure formed carbon-rich coal between layers of sedimentary rock. • OIL: • Microscopic aquatic organisms died & settled to bottom. • Their decay lowered the O2, further slowing decay. • Formed hydrocarbon mixture called Oil. • NATURAL GAS: • Same way as Oil, only at higher temperatures.
COAL • 4 types: • Lignite, Sub-Bituminous, Bituminous, Anthracite • How do the following change: • Color? • Water content? • Sulfur Content? • Carbon Content? • Avg. Heat Value (BTU/Pound)? • Cost? • Coal Reserves Worldwide
Surface Mining Control & Reclamation Act (1977) • Surface mines can have substantial effects on the environment • Large open pits or trenches • Acid and toxic mineral drainage • Dangerous landslides • Restorations were half hearted • SMCRA requires coal companies to restore areas. Reclamation begins during the mining process, not after mining ends
Problems with Coal? • Brainstorm!!! • Safety issues: • Mine collapses, disease (Black Lung) • Environmental Issues: • Land disruption (open pit mines, mountain top removal), acid mine drainage, increased erosion, sediment pollution in streams, landslides • Air emissions (CO2, Sulfur&Nitrogen oxides, acid deposition – and acidification of lakes/streams)
Making Coal a Cleaner Fuel • SCRUBBERS • Recall: uses mist of water to remove precipitates • Can sell the sludge to manufacturers: • Sludge can make: Wallboard, soil conditioner • Fly Ash an make: lightweight concrete • CLEAN COAL TECHNOLOGIES • 1 – Fluidized-Bed Combustion • Mix crushed coal w/ limestone & O2 at low temps. • Produces fewer nitrogen oxides • Produces NO sulfur oxides (sulfur mixes with the limestone) • 2 – Coal Gasification • Mix crushed coal w/ steam & air to produce CH4 & CO2! • Sulfur is naturally removed, so no scrubbers are needed. NOTE: “Clean Coal” isn’t perfect – still have CO2 released!
OIL & NATURAL GAS • Petroleum / Crude Oil • Hundreds of hydrocarbon compounds • How is it created??? • Microscopic aquatic organisms don’t decay much. Sediment piles on top, and they become oil! • How are they separated? • Based on boiling points! • Fractional Distillation
Structural Traps • How Oil & Natural gas form… • They migrate upward (low density) and are trapped by impermeable rock layers.
Who’s got it?? • OIL: mostly in the Persian Gulf • NATURAL GAS: mostly in Russia & Iran ALSO: Much may be found in the cont. shelf!
How long will it last? • Difficult to say… • Oil production will peak between 2010 & 2020. • Improving tech will allow us to extract more & produce oil from natural gas, coal & synfuels. • Then the oil peak will move to 2050 – 2100
Dependence of the United States and other countries on Middle Eastern oil has potential international security implications as well as economic impacts.
Environmental Problems with Oil & Natural Gas • Burning (combustion), obtaining fuels (production & transport) • Increased carbon dioxide emissions • Every gallon of gas releases 20lb. of carbon dioxide • Acid deposition (Nox) • Natural Gas does not pollute as much as oil • Relatively clean, efficient source with almost no S • Produces less CO2, fewer hydrocarbons and few particulate matter
Exxon Valdez (1989) • Supertanker hit Bligh Reef • Spilled 10.9 million gallons of crude into Prince William Sound, Alaska • Killed a LOT of wildlife • 30,000 birds (ducks, loons, cormorants, eagles) • 3,500- 5,000 sea otters • Killer whale & harbor seal population disrupted • Salmon migration disrupted • No fishing for the year in the area • Cleaned the area using mechanized steam cleaning and rinsing (killed shoreline organisms) • Cost estimated at 10 billion • OIL POLLUTION ACT (1990) • Established liability for damages to natural resources resulting from spills • Requires double hulls on all oil tankers that enter US waters.
Persian Gulf Oil Spill (1991) • 250 mill gallons of crude were dumped into the Persian Gulf (6x that of Exxon). • Oil wells were set on fire & lakes of oil spilled into the desert • Initial cleanup efforts hampered by the war.
Arctic National Wildlife Refuge • 1980 NE Alaska declared wilderness area. • ~7.7 B barrels of oil within the refuge • Bush supports opening refuge to drilling. • Senate voted against development 2002. • Continues to be debated today in congress. • Conservationists believe that oil exploration posed permanent threats to the delicate balance of nature in the Alaskan wilderness.
Synfuels • “Synthetic Fuels” • Derived from coal & other natural sources • Liquid or gaseous • Include: • Tar sands • Oil shales • Gas hydrates • Liquefied coal • Coal gas Remember: They’re alternatives, but they’re not perfect!!! …Lots of CO2 emissions!
Synfuels: Tar Sands • aka “Oil Sands” • Sand deposits permeated with thick oil called bitumen. • Must be heated underground to make it fluid enough to pump. • Must be refined like crude oil • Lots of it! • (1/2 again as much fuel as world oil reserves) • Reserves in Venezuela & Canada
Synfuels: Oil Shales • Rocks containing a mixture of hydrocarbons called kerogen. • Must be crushed & heated, and kerogen must be refined. • Not yet cost efficient, although there’s lot of it! • Reserves in Australia, Estonia, Brazil, Sweden, USA, China
Synfuels – Gas Hydrates • aka “Methane Hydrates” • Ice-encrusted natural gas • Deposits in • Arctic Tundra (deep below permafrost) • Deep ocean sediments • Expensive to mine • Reserves in Russia
Coal Liquefaction Nonalcoholic liquid (similar to oil) Produced from coal Less polluting than solid coal Too expensive now Coal Gasification Produce combustible methane C + H2O CH4 + CO2 Burns almost as cleanly as natural gas Synfuels
US Energy Policy! • Increase energy efficiency & conservation • Low $ encourages high consumption… should we increase the price?? • Gov’t Subsidies reduce the price to stimulate the economy • Gov’t Taxes increase the price to generate revenue • Which is better??? • Secure future fossil fuel energy supplies • Only a temporary strategy… • Develop alternative energy sources • Gasoline tax may help this… • Accomplish the first three objectives without further damaging the Environment • Duh!! Remember… Policies change every 4-8 years
NUCLEAR ENERGY • Energy released in combustion reactions comes from changes in the chemical bonds that hold the atom together. • Nuclear Energy involves changes within the nuclei of the atom. Small amounts of matter from the nucleus are converted into large amounts of energy • Fission: Larger atoms of certain elements are split into smaller atoms of certain elements. Power Plants. • Fusion: 2 smaller atoms are combined to make 1 large atom of a different element. Mass of the end product is less than the mass of the starting materials released as energy. The Sun.
The Atom Neutron Atomic Number: # of protons Atomic Mass: # of protons + # of neutrons Proton Nucleus Electron Isotope: forms of a given element with different numbers of neutrons therefore different atomic masses. ex)Hydrogen has 1 P and no N Deuterium has 1 P and 1 N Tritium has 1 P and 2 N As a radioactive element emits radiation, its nucleus changes into the nucleus of a different element that is more stable…. Radioactive decay.
Each radioisotope has its own characteristic rate of decay. • Half-Life: the period of time required for one half of the total amount of a radioactive substance to change into a different material. • Iodine- 131 0.02 years ( 8.1 days) • Krypton-85 10.4 years • Plutonium- 239 24,400 years • Uranium • U-235: produces a fission chain reaction • Critical mass: amount of U-235 required to start a chain reaction • Less than 1% of all uranium is U-235 • Known as enriched uranium
URANIUM & PLUTONIUM • U-235: produces a fission chain reaction • Critical mass: amount of U-235 required to start a chain reaction • Less than 1% of all uranium is U-235 • Known as enriched uranium • Half life: 700 million years • U-238 • Most common (99.3%) • Half life of 4.5 billion years • When hit by a neutron it decays into PU-239 • PU-239 • Produced in breeder reactors from U-238 • Half life of 24,000 years • Regulated by international inspections because it can be used in nuclear weapons.
Nuclear Fuel Cycle • Mining • Enrichment (refining process) • Fuel rods • Fuel assemblies (200 rods) • Reactor (~ 250 fuel assemblies) • Fuel is used • Fuel is reprocessed • Fuel is disposed of or sent for enrichment.
Uranium Fission:U-235 is bombarded with neutrons and absorbs a neutron becoming unstable and splits into 2 smaller atoms. Two or 3 neutrons are ejected and collide with other U-235 causing a chain reaction. This releases an enormous amount of heat steam ENERGY!!!
How is electricity produced?? • Reactor core- heat produced by nuclear fission is used to produce steam from liquid water. • Steam generator- uses steam turn a turbine • Turbine- generates electricity from steam • Condenser- cools the steam converting it back to a liquid. Above each reactor core is a control rod made of metal alloy capable of absorbing neutrons. The plant will move this up and down depending on the energy needs throughout the day.
Nuclear Power Plant SAFETY…The reactor is surrounded by a huge steel pot like structure called a reactor vessel. Reactor vessel & steam generator are placed in a containment building.
Three Water Circuits • Primary water circuit(orange in fig 11.5) • Heats water using energy produced by the fission rxn. • Circulates water under high pressure through the core • Superheated water cannot expand stays liquid. • Secondary Water Circuit(blue in fig 11.5) • Convert the water to steam • Tertiary Water Circuit(green in fig 11.5) • Provides cool water to the condenser cooling off spent steam in the secondary water circuit. • Water moves to a cooling tower or lake.
Breeder Nuclear Fission • Uranium is mostly U-238 (not fissionable) • U-238 is converted to Plutonium (Pu-239) which is fissionable • Some neutrons emitted are used to produce additional plutonium from U-238. A breeder reactor makes more fissionable fuel than it uses!!!! Since breeder reactors can use U-238, it has the potential to generate much larger quantity of energy from uranium than traditional nuclear fission. Old waste from plants in the form of U-238 could be used as fuel.
Is Nuclear Energy Cleaner? • Supporters say nuclear energy is better than alternatives because it is less polluting and more economical and its fuel is plentiful. • Spent fuel & wastes are the only major concerns. • Opponents refute these arguments. • We should look at clean coal options • Nuclear does not significantly lessen GW b/c only 15% of greenhouse gasses are produced by plant. • Uranium mining requires the combustion of fossil fuels.
Cost of Nuclear Power • 104 nuclear power plants supply about 23% of US electricity. • The US has not ordered a nuclear power plant since 1976. • High cost • Take years to plan & build • Nuclear regulatory process is cumbersome & expensive. • Nuclear Regulatory Commission must oversee all steps in planning and building each site.
SAFETY in Nuclear Power Plants • MELTDOWN = at high temperatures, the metal that encases the uranium fuel melts, releasing radiation. • Also, the water used in a nuclear reactor can boil away, releasing radiation into the atmosphere. • Two case studies: • THREE MILE ISLAND (Eastern Pennsylvania) • CHORNOBYL (Former USSR – now Ukraine)
Three Mile Island, PA -1979 • Result of human error after cooling system failed. • 50% meltdown • Containment building kept almost all radioactivity from escaping • No substantial environmental damages and no immediate human casualties • After 10 years, the only human health problem was increased stress. • Increased public wariness, and caused new safety regulations to be enacted.
Chornobyl, USSR -1986 • 1 or 2 explosions destroyed the nuclear reactor • Only 100% meltdown in world history • Radiation quickly spread across Europe • Human effects: • Many firefighters containing the fire later died • 170,000 people had to permanently abandon their homes • Death toll (as of 1999) was almost 170,000 • Nearly 400,000 adults and over 1 million children currently receive government aid for health problems • Thyroid Cancer, leukemia, immune problems, birth defects… • Soil/farmland was severely damaged
Chornobyl, USSR -cont • What happened?? • Design of the reactor was flawed • no containment unit & unstable at low power • This type of reactor (RBMK) is not used in North America or Western Europe (too unsafe) • Adjacent countries still use it! • Human error • Many plant operators had no training! • How was it fixed?? • Entombed the destroyed reactor in a “sarcophagus” • Recent inspections have revealed safety hazards • Numerous cracks in the sarcophagus • $$$ to fix it – international donors are helping out.
Link to Nuclear Weapons • Spent Fuel Rods from nuclear energy reactors can be used to make bombs • Storing it is a nightmare (security issue) • Only a few kilograms are needed to make a bomb as strong as the Nagasaki/Hiroshima bombs • Russian Political instability makes us nervous… • Former USSR has enough highly enriched uranium and plutonium to make 40,000 nuclear bombs. • Big push in the international community to help Russia maintain nuclear security. • IRAN- Do you watch the news?!?! • US plans to get rid of over 50 tons of surplus plutonium from dismantling our warheads. • Will be converted to MOX (mixed oxide), then burned as fuel in commercial power reactors.