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Tidal Power

Tidal Power. Energy conversion – kinetic to electrical Benefits – pollution-free, cheap, renewable Costs – only two places in the U.S. have tides needed to do this. Wave Power. Energy conversion – kinetic to electrical Benefits – pollution-free, cheap, renewable

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Tidal Power

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  1. Tidal Power • Energy conversion – kinetic to electrical • Benefits – pollution-free, cheap, renewable • Costs – only two places in the U.S. have tides needed to do this

  2. Wave Power • Energy conversion – kinetic to electrical • Benefits – pollution-free, cheap, renewable • Costs - only suitable in areas facing the open ocean (especially on the West Coasts of continents); tend to be destroyed in storms

  3. PRODUCING ELECTRICITY FROM THE WATER CYCLE • Ocean tides and waves and temperature differences between surface and bottom waters in tropical waters are not expected to provide much of the world’s electrical needs. • Only two large tidal energy dams are currently operating: one in La Rance, France and Nova Scotia’s bay of Fundy where the tidal amplitude can be as high as 16 meters (63 feet).

  4. NUCLEAR ENERGY • When isotopes of uranium and plutonium undergo controlled nuclear fission, the resulting heat produces steam that spins turbines to generate electricity. • The uranium oxide consists of about 97% nonfissionable uranium-238 and 3% fissionable uranium-235. • The concentration of uranium-235 is increased through an enrichment process.

  5. 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) Fig. 16-16, p. 372

  6. NUCLEAR ENERGY • 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. Figure 16-17

  7. NUCLEAR ENERGY • After spent fuel rods are cooled considerably, they are sometimes moved to dry-storage containers made of steel or concrete. Figure 16-17

  8. 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.

  9. Case Study: The Chernobyl Nuclear Power Plant Accident • The world’s worst nuclear power plant accident occurred in 1986 in Ukraine. • The disaster was caused by poor reactor design and human error. • By 2005, 56 people had died from radiation released. • 4,000 more are expected from thyroid cancer and leukemia.

  10. NUCLEAR ENERGY • A 1,000 megawatt nuclear plant is refueled once a year, whereas a coal plant requires 80 rail cars a day. Figure 16-20

  11. Trade-Offs Coal vs. Nuclear Coal Nuclear Ample supply of uranium Ample supply Low net energy yield High net energy yield Low air pollution (mostly from fuel reprocessing) Very high air pollution Low CO2 emissions (mostly from fuel reprocessing) High CO2 emissions High land disruption from surface mining Much lower land disruption from surface mining High land use Moderate land use High cost (even with huge subsidies) Low cost (with huge subsidies) Fig. 16-20, p. 376

  12. NUCLEAR ENERGY • Terrorists could attack nuclear power plants, especially poorly protected pools and casks that store spent nuclear fuel rods. • Terrorists could wrap explosives around small amounts of radioactive materials that are fairly easy to get, detonate such bombs, and contaminate large areas for decades.

  13. NUCLEAR ENERGY • When a nuclear reactor reaches the end of its useful life, its highly radioactive materials must be kept from reaching the environment for thousands of years. • At least 228 large commercial reactors worldwide (20 in the U.S.) are scheduled for retirement by 2012. • Many reactors are applying to extent their 40-year license to 60 years. • Aging reactors are subject to embrittlement and corrosion.

  14. NUCLEAR ENERGY • Building more nuclear power plants will not lessen dependence on imported oil and will not reduce CO2 emissions as much as other alternatives. • The nuclear fuel cycle contributes to CO2 emissions. • Wind turbines, solar cells, geothermal energy, and hydrogen contributes much less to CO2 emissions.

  15. NUCLEAR ENERGY • 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.

  16. Nuclear • Description – using fission to split large uranium atoms into smaller products and releasing tremendous amounts of heat energy which is used to make steam that turns turbines to create electricity • Energy conversion – nuclear to electrical and heat • Benefits – pollution-free, very, very efficient • Costs – risk of accidents (spread of radioactivity); transportation and disposal of radioactive wastes (Nimby!) It also produces a ton of thermal pollution!

  17. WAYS TO IMPROVE ENERGY EFFICIENCY • We can save energy in building by getting heat from the sun, superinsulating them, and using plant covered green roofs. • We can save energy in existing buildings by insulating them, plugging leaks, and using energy-efficient heating and cooling systems, appliances, and lighting.

  18. Strawbale House • Strawbale is a superinsulator that is made from bales of low-cost straw covered with plaster or adobe. Depending on the thickness of the bales, its strength exceeds standard construction. Figure 17-9

  19. Living Roofs • Roofs covered with plants have been used for decades in Europe and Iceland. • These roofs are built from a blend of light-weight compost, mulch and sponge-like materials that hold water. Figure 17-10

  20. Saving Energy in Existing Buildings • About one-third of the heated air in typical U.S. homes and buildings escapes through closed windows and holes and cracks. Figure 17-11

  21. Approximate Energy Efficiencies: • Photosynthesis: 1% • Incandescent light bulbs: 95%

  22. Definition Alternative Fuels • Any fuel that meets certain emissions standards; i.e. they give off a certain amount of pollution (or less)

  23. Laws Involved • Clean Air Act amendments of 1990 • Energy Policy Act (EPACT) in Texas of 1992 • Such laws have led to more research and development of these fuels

  24. Examples of Alternative Fuels • Biodiesel – made of vegetable oils and alcohols; expensive • Diesel – cleaner than “normal” gasoline, being more refined • Biogas – by-product of decaying vegetation; need technology • Hydrogen – expensive and we need more technology

  25. Ethanol/Methanol – alcohols; not as efficient (Miles per gallon) and we don’t have all the technology ; also, if our grain supplies are used to make fuel, will we have enough to feed the world? • Natural Gas – expensive and we need more technology • Reformulated Gasoline (RFG) – regular gas that has been further refined to remove some of the more toxic pollutants

  26. Propane – most usable form of alternative fuel; not as efficient (mpg) • Syngas – manmade gas made of hydrogen and carbon monoxide; need more technology to use it

  27. HYDROGEN • Some energy experts view hydrogen gas as the best fuel to replace oil during the last half of the century, but there are several hurdles to overcome: • Hydrogen is chemically locked up in water an organic compounds. • It takes energy and money to produce it (net energy is low). • Fuel cells are expensive. • Hydrogen may be produced by using fossil fuels.

  28. Energy Laws • Public Utility Holding Company Act (PUHCA) – 1935; regulated the interstate flow of energy; 1st law of its kind; a law designed to protect consumers from corporate abuse of electricity markets • (so electric companies can’t price gouge.) This was happening during the great depression.

  29. Corporate Average Fuel Economy Act (CAFÉ) –1975; focused attention on efficiency of cars; mpg stickers required • Public Utility Regulatory Policies Act (PURPA)–1978; higher utility rates for increased electricity use

  30. Converting Plants and Plant Wastes to Liquid Biofuels: An Overview • Motor vehicles can run on ethanol, biodiesel, and methanol produced from plants and plant wastes. • The major advantages of biofuels are: • Crops used for production can be grown almost anywhere. • There is no net increase in CO2 emissions. • Widely available and easy to store and transport.

  31. Case Study: Producing Ethanol • Crops such as sugarcane, corn, and switchgrass and agricultural, forestry and municipal wastes can be converted to ethanol. • Switchgrass can remove CO2 from the troposphere and store it in the soil. Figure 17-26

  32. Case Study: Producing Ethanol • 10-23% pure ethanol makes gasohol which can be run in conventional motors. • 85% ethanol (E85) must be burned in flex-fuel cars. • Processing all corn grown in the U.S. into ethanol would cover only about 55 days of current driving. • Biodiesel is made by combining alcohol with vegetable oil made from a variety of different plants..

  33. Case Study: Biodiesel and Methanol • Growing crops for biodiesel could potentially promote deforestation. • Methanol is made mostly from natural gas but can also be produced at a higher cost from CO2 from the atmosphere which could help slow global warming. • Can also be converted to other hydrocarbons to produce chemicals that are now made from petroleum and natural gas.

  34. WAYS TO IMPROVE ENERGY EFFICIENCY • Average fuel economy of new vehicles sold in the U.S. between 1975-2006. • The governmentCorporate Average Fuel Economy (CAFE) has not increased after 1985. Figure 17-5

  35. Cars Average fuel economy (miles per gallon, or mpg) Both Pickups, vans, and sport utility vehicles Model year Fig. 17-5, p. 388

  36. WAYS TO IMPROVE ENERGY EFFICIENCY • General features of a car powered by a hybrid-electric engine. • “Gas sipping” cars account for less than 1% of all new car sales in the U.S. Figure 17-7

  37. Regulator: Controls flow of power between electric motor and battery bank. Fuel tank: Liquid fuel such as gasoline, diesel, or ethanol runs small combustion engine. Transmission: Efficient 5-speed automatic transmission. Battery: High-density battery powers electric motor for increased power. Combustion engine: Small, efficient internal combustion engine powers vehicle with low emmissions; shuts off at low speeds and stops. Electric motor: Traction drive provides additional power for passing and acceleration; excess energy recovered during braking is used to help power motor. Fuel Electricity Fig. 17-7, p. 389

  38. Hybrid Vehicles, Sustainable Wind Power, and Oil imports • Hybrid gasoline-electric engines with an extra plug-in battery could be powered mostly by electricity produced by wind and get twice the mileage of current hybrid cars. • Currently plug-in batteries would by generated by coal and nuclear power plants. • According to U.S. Department of Energy, a network of wind farms in just four states could meet all U.S. electricity means.

  39. Fuel-Cell Vehicles • Fuel-efficient vehicles powered by a fuel cell that runs on hydrogen gas are being developed. • Combines hydrogen gas (H2) and oxygen gas (O2) fuel to produce electricity and water vapor (2H2+O2 2H2O). • Emits no air pollution or CO2 if the hydrogen is produced from renewable-energy sources.

  40. Body attachments Mechanical locks that secure the body to the chassis Air system management Universal docking connection Connects the chassis with the drive-by-wire system in the body Fuel-cell stack Converts hydrogen fuel into electricity Rear crush zone Absorbs crash energy Drive-by-wire system controls Cabin heating unit Side-mounted radiators Release heat generated by the fuel cell, vehicle electronics, and wheel motors Hydrogen fuel tanks Front crush zone Absorbs crash energy Electric wheel motors Provide four-wheel drive; have built-in brakes Fig. 17-8, p. 390

  41. National Appliance Energy Act – 1987; energy efficiency stickers on all appliances

  42. Renewable Energy and Technology Competitiveness Act – 1989; effort to develop renewable energy nationally • Clean Air Act Amendments – 1990; set standards for cities and emissions • Energy Policy Act – 1992; comprehensive effort to find renewable energy resources

  43. Hydrogen Future Act – 1996; develop hydrogen as an energy source • PROBLEM – FEW of these actually provide the money needed to research renewable resources

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