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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
    • FUSION
      • 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