Energy Alternatives

1. Energy Alternatives

2. Nuclear energy

3. Fission • Nuclear energy = energy holding protons and neutrons together • Nuclear energy → thermal energy → electricity • In nuclear power plants, nuclear fission drives the release of energy • In fission, a large, unstable nucleus (U-235 or U-238), is made to break apart, releasing energy • Radioisotopes are atoms of a certain element that emit subatomic particles and radiation to become stable

6. Fission • Each radioisotope has a certain half-life of decay • Half-life is the time it takes for half of the original amount of radioactive isotope to decay • After several years, rods must be replaced due to decay and consumption • Fuel rods can be processed to extract more energy, but they are usually disposed of as radioactive waste

7. Fission • Breeder reactors make use of 238U which can generate more power (it is more abundant than 235U) • Breeder reactors use liquid Na as coolant – more dangerous • Breeder reactors can generate plutonium to be used in nuclear weapons

8. Fusion • Fusion involves the synthesis of heavier elements from lighter ones under high temperature and pressure • Hydrogen isotopes (deuterium and tritium) are fused to form helium • Have not achieved break-even energy • Energy is cleaner, resources are plentiful (water)

10. Nuclear Advantages & Disadvantages • Clean energy (no emissions) • More bang for your buck means less mining • Disposal of waste is a huge problem; most is stored on site • Accidents, sabotage could be catastrophic • 439 operating plants world-wide

11. Small Risks of Large Accidents • 1979 – Three Mile Island in Pennsylvania • Metal surrounding the fuel rods melted down, releasing radiation • It did not escape containment (some gases were vented) • Clean-up lasted years • No significant health risks

13. Small Risks of Large Accidents • 1986 – an explosion at the Chernobyl plant (Ukraine) caused most severe nuclear pp disaster in the world • Clouds of radioactive debris spewed into the atmosphere • Fallout carried over most of northern hemisphere • 30-km radius contaminated

15. Waste Disposal & Other Problems • Waste remains dangerous for thousands of years (remember half-life?) • Currently, waste is held in temporary storage on-site • Yucca mountain in Nevada has been chosen for storage beginning in 2010 • More expensive than expected • Plants have aged more quickly • Shutting down plants more expensive than the original construction

16. Biomass energy

17. Biomass Energy • Biomass consists of the organic material that makes up living organisms • Biomass energy involves burning many types of plant and animal matter • Includes: wood, charcoal, combustible animal waste • Fuelwood and other traditional biomass sources = 80% of all renewable energy used worldwide • Renewable if not overharvested!

18. Biomass Energy • Biopower generates electricity in power plants • Biomass sources can be converted to biofuels • Many new biomass resources are waste products from preexisting industry • Organic components form municipal landfills, animal waste from feedlots and ag residue can be major bioenergy resources

20. Biofuels • Ethanol is produced by fermenting biomass • Used in gasoline to reduce emissions • E-85 is 85% ethanol and 15% gasoline • Biodiesel is produced from vegetable oil, used cooking grease or animal fat • Traditional diesel engines can run on 100% biodiesel

21. Environmental and Economic Benefits • Carbon-neutral, releasing no net carbon into the air • Is the product of recent photosynthesis, so carbon released balances the carbon taken up • Capturing landfill gas for biofuels also reduces greenhouse gases • Ethanol additives to gasoline reduces pollution • Economic support of rural areas, reduce dependence on oil, etc. • Human health benefits

22. Drawbacks • Burning biomass in traditional ways for cooking and heating leads to health hazards from indoor pollution • Unsustainable harvesting leads to deforestation, erosion, and desertification • Growing biofuel crops leads to monoculture agriculture • Growing biofuel crops requires large energy inputs

23. Hydroelectric power

24. Hydroelectric Power • Kinetic energy of moving water powers turbines to generate electricity • Most of our energy comes from impounding water behind dams and letting water pass through dams • An alternative is run-of-river approach, in which electricity is generated w/out disrupting water flow (susceptible to seasonal changes)

25. Hydroelectric Power • Hydropower is widely used • Hydropower is clean and renewable • Negative impacts include habitat destruction, disruption of natural flooding, sediments trapped behind the dam, thermal pollution downstream, fragmentation of the river • No room for expansion – all capable rivers already dammed (98% in US)

26. “new” renewable energy

27. Currently Provide Little of Our Power • 80% of world’s energy sources are fossil fuels • US electricity generation from renewables: • 75% hydropower • 17.5% biomass • 4.2% geothermal • 4.1% wind • 0.1% solar

28. Currently Provide Little of Our Power • Transition cannot be immediate, but it must be soon: • Expensive • Technology must be developed • Lack of infrastructure to transfer energy • Labor intensive (good for economy – jobs) • Development is underfunded

29. Solar energy

30. Solar Energy • Potential is tremendous; the sky is the limit! • Passive solar heating: buildings and materials are chosen to maximize direct absorption of sunlight in winter • Active solar energy collection uses technological devices to focus, move, or store energy

31. Solar Energy • Passive: heat-absorbing materials, low, south-facing windows, even vegetation • Active: uses solar panels or flat-plate solar collectors • Concentrating solar rays magnifies energy received • Photovoltaic (PV) cells convert sunlight into electricity

32. Solar Energy • PV cells made of silicon enriched with P and B • Solar power is little used, but growing fast • Sales of PV growing by 28% each year in US • Limitless supply of energy (well, at least 4 billion years more) • PVC’s use no fuel, are quiet, little maintenance, do not require a turbine or generator

33. Solar Energy • Enable local, decentralized control over power • No pollution • Location and cost are major drawbacks • Need a sunny region

35. Wind energy

36. Wind Energy • Indirect solar energy! • Wind turbines convert KE of wind into electricity • Over 800 years of use, first generation of electricity in late 1800’s • Most turbines are erected in groups called wind farms

37. Wind Energy • Designed to begin turning at specific wind speeds • Offshore sites more productive • No emissions are produced • More energy efficient than conventional • Can be used on many scales • Landowners can lease land

38. Wind Energy • Up-front costs are large, but low lifetime costs for upkeep • Generation relies on wind • Good wind resources not always near populated areas • Threat to birds (not owls – they’re too smart)

39. Wind Energy • Noise is an issue for those who live nearby • Wind is intermittent

40. Geothermal energy

41. Geothermal Energy • Originates from deep underground • Radioactive decay of elements and high pressures generates heat; rises to sfc • Requires well-drilling 100’s to 1000’s of meters to tap heated groundwater • Can be used directly for heating homes, etc

42. Geothermal Energy • Can also be used to drive a heat pump • Ground Source Heat Pumps (GSHP) are 50-70% more efficient than conventional • Reduces emissions • Water is loaded with salts that lead to corrosion of equipment • Use in particular areas only

43. Ocean energy sources

44. Ocean Energy Sources • Harnessing energy from tides and ocean waves • Other: currents, chemical gradients (salinity), and immense thermal energy

45. hydrogen

46. Hydrogen Fuel Cells • Shows promise as a vehicle for storing electricity conveniently in large quantities • Produced from water through electrolysis • Fuel cells produce electricity by combusting hydrogen • Hydrogen is most abundant element in universe

47. Hydrogen Fuel Cells • It is clean and nontoxic • May produce a few pollutants and greenhouse gases, depending on source of H • Fuel cells are quiet, non-polluting and allow energy to be stored in the form of H • Energy efficient