Ch 17 alternative energy sources
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Ch 17 alternative energy sources






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Ch 17 alternative energy sources Ch 17 alternative energy sources Presentation Transcript

  • Ch 17 Alternative Energy Sources 17.1 Solar Energy
    • Icarus
    • Energy from the sun- solar energy, used as fuel for all organisms
    • Drives water cycle
    • Creates winds
    • Sun’s energy comes from fusion reaction
    • Light nuclei- like hydrogen Combine to form a heavier nuclei, helium, In the process a small amount of mass is converted to lots of energy
    • Earth gets only 1/1,000,000,000 of energy from the sun, mostly as infrared and visible light
    • Energy cannot be created nor destroyed, but it can change form, and so solar energy can be converted into heat ( or thermal) energy, electricity,
    • It can replace fossil fuels, biomass fuels and nuclear in some areas
  • Advantages of Solar
    • Clean- nonpolluting
    • Free
    • Cost can be recovered in reduced fuel costs
  • Disadvantage
    • Not steady- must live in a sunny area
    • Devices for storing solar energy need to be improved
    • Size of collectors and cost may be prohibitive
  • Passive Solar
    • Sun’s energy is collected, stored and distributed naturally in an enclosed dwelling
    • Examples: greenhouse, car on sunny day
    • Passive solar homes are well designed to take advantage of the sun.-large windows that face south, building materials that absorb the sun’s heat ( stone, brick, concrete), dark colors, glass ( greenhouse idea), sometimes water-filled barrels ( water absorbs large amounts of heat), good insulation
  • Active Solar Energy
    • Devices are used to collect, store and circulate heat from the sun
    • Uses tubes, tanks, pumps, fluids, fans
    • Solar collectors collect the sun’s energy- usually placed on a roof- called flat-plate collectors
    • Flat-plate collectors are painted black, and have system of tubes filled with fluid (water, antifreeze or air). Look at pg 268
    • Heated fluid is pumped to a storage area, where it can be pumped to other areas of the house. As fluid cools it can be pumped back to the collector
    • Used in Israel, Japan, India and West Indies- can be cost effective
    • Read about Solar One ( pg 268)
  • Photovoltaic Cells
    • The photovoltaic cell takes the sun’s energy and converts it directly into electricity (PV cell)
    • PV cell is a thin wafer made of semiconductors ( Si, Se)
    • Electrons move from one wafer to another when sun’s rays strike the semiconductor.
    • Movement of electrons is electricity
    • PV cells- found in calculators, watches, satellites use them
    • Engineers working on solar powered cars