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Chapter 9

Chapter 9. Energy Sources. Section 1. Fossil Fuels. Using Energy. Thermal, electrical, mechanical energy – ALL the time Use means transform energy from one form to another Useful and non-useful transformations. Use in the US. We use more energy than anyone else in the world.

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Chapter 9

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  1. Chapter 9 Energy Sources

  2. Section 1 Fossil Fuels

  3. Using Energy • Thermal, electrical, mechanical energy – ALL the time • Use means transform energyfrom one form to another • Useful and non-useful transformations

  4. Use in the US • We use more energy than anyone else in the world

  5. Making Fossil Fuels • Fossil Fuels – petroleum, oil, coal, and natural gas formed from decaying ancient plants and animals over millions of years • Combustion reactions take chemical potential energy  heat and light • Fossil Fuels – energy is concentrated

  6. Petroleum • Def: (crude oil) highly flammable liquid formed by decayed ancient organisms • Hydrocarbon – contain only hydrogen and carbon • Contains many dif. Hydrocarbons • Separate by Fractional Distillation – tall towers of refineries • Heat and dif. hydrocarbons have dif. boiling points • Lowest bp on top – highest on bottom (liquid asphalt)

  7. Petroleum Uses • Plastics and synthetic fabrics • Grease, Vaseline, motor oil

  8. Natural Gas • Rise to top of petroleum deposits in ground • Contains Methane CH4, Propane C3H8 and Butane C4H10 • Makes up ¼ of energy consumed in US • More energy than petr. and burns cleaner

  9. Coal • Until 1950s almost half energy in US was from coal • Today it is ¼ and 90% is used to make electricity in power plants

  10. Origin of Coal • Coal mines were once swamps • Estimated 20 – 40 times more coal than petroleum • Coal not as pure as other Fossil Fuels – has more sulfur and nitrogen • Leads to more pollutants

  11. Generating Electricity

  12. Generating Electricity • Burn fuel – thermal energy – heat water – steam – spins turbine – spins magnet in generator – electricity!

  13. Generating Electricity

  14. Efficiency

  15. Cost of Using Fossil Fuels • Burning Coal and Petroleum give off particulates – can cause breathing problems • CO2 given off = global warming • Coal – very dirty – sulfur pollutants = acid rain • Mining is very dangerous

  16. Nonrenewable Resources • Def: cannot be replaced as quickly as being used • Increase cost = more difficult to get • Push for “renewable” sources to help energy demand

  17. Chapter 9 Section 2 Nuclear Energy

  18. Using Nuclear Energy • No Fossil Fuels • Nuclear energy (energy released when nucleus breaks apart – nuclear fission)  electrical energy • 20% of electricity produced in US • In 2003 – 104 nuclear reactors in 65 nuclear power plants in US

  19. Nuclear Reactors • Def: uses energy from controlled nuclear reactions to generate electricity • Fuel – undergoes fission • Control rods – control reaction • Cooling system • Core is very small part

  20. Nuclear Fuel • Only certain elements can undergo fission • Uranium, U-235 • Fuel normally uranium dioxide • Use enriched Uranium so its 3-5% U-235 • Fuel is in tiny pellets • Core has 100,000 kg of uranium • In 100s of fuel rods • 1 kg U undergoes fission = • Energy of 3 million kg of coal

  21. Nuclear Fission • A nuclear chain reaction happens in milliseconds • # nuclei at each stage doubles  after 50 stages a quadrillion nuclei may split • If not controlled, will release energy explosively

  22. Controlling Reactions • Control rods absorb some neutrons • Moving the rods deeper in the core  absorb more neutrons = slows reaction • Eventually energy is released at a constant rate

  23. Nuclear Power Plants • Energy released by fission = thermal energy – heats steam, etc. • Efficiency is 35%

  24. The Risks! • Good = no fossil fuels, no pollutants • Bad: • Mining of U has environmental problems • Water used needs to cool before released in streams • Escape of harmful radiation – have elaborate safety systems • p. 268

  25. Disposal of Waste • After 3 years U-235 is spent = Nuclear Waste – radioactive by products • Low-level wastes – clothing exposed to radiation, air filters or smoke detectors • Buried in sealed containers 30 m deep

  26. Disposal Tanks • High-level wastes – power plants and weapons • Stored in deep pool of water • Sealed in ceramic glass in metal-alloy containers buried 100s of meters – won’t contaminate for 1000s of years

  27. Chapter 9 Section 3 Renewable Energy Sources

  28. Renewable Resources • Def: Energy source replaced nearly as quickly as used • Energy from Sun: • Amt of solar energy falls on US in a day is more than energy used in 1 year • Photovoltaic Cell: (solar cell) take radiant solar energy  electrical energy • 7-11% efficient

  29. How Solar Cells Work • Sunlight hits e-rich semiconductor  e-poor semiconductor = electric current sent through metal

  30. Using Solar Energy • Solar electricity is more expensive but in remote areas it is good • Best way is a parabolic trough – focuses sunlight on tube – synthetic oil or liquid salt • Heat liquid  heats water = steam to spin generator • Plant in the Mojave Desert = 9 units, 350 megawatts – 500,000 people

  31. Energy from Water • Hydroelectricity: electricity produced from energy of moving water • Produces 8% of electricity used • Twice as efficient because of no heat and no pollutants

  32. Energy from Water • Problems: • Artificial dams damage natural ecosystem • Water reservoirs aren’t everywhere

  33. Energy from Tides • Rising tide comes in – spins turbines and is trapped • Decreasing tide flows back out – spins turbines • Need to have tide dif of 5 m • 1 in North America – Annapolis Royal, Nova Scotia – tide dif 17 m

  34. Harnessing the Wind • Wind spins propeller – connected to generator • Few places have constant wind • 20% efficient • Noisy – change appearance of landscape

  35. Energy from Inside Earth • Decay of radioactive elements = geothermal heat  makes magma • Geothermal Energy: thermal energy in hot magma • Old Faithful – water heated by magma close to surface

  36. Energy from Inside Earth • Water pumped in ground – heated – steam released • 16% efficient • Can release sulfur compounds • Limited to areas where magma is close to surface

  37. Alternative Fuels • Hybrid vehicles – use electric batteries and gasoline • Hydrogen gas – produces only water vapor when burned • Biomass Fuels: renewable organic matter, wood, sugarcane fibers, rice hulls, and manure • Burned in oxygen to convert chemical energy  thermal energy  heat water, etc.

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