Ch 17 alternative energy sources

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Ch 17 alternative energy sources

  1. 1. Ch 17 Alternative Energy Sources 17.1 Solar Energy
  2. 2. <ul><li>Icarus </li></ul><ul><li>Energy from the sun- solar energy, used as fuel for all organisms </li></ul><ul><li>Drives water cycle </li></ul><ul><li>Creates winds </li></ul><ul><li>Sun’s energy comes from fusion reaction </li></ul>
  3. 3. FUSION <ul><li>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 </li></ul>
  4. 4. <ul><li>Earth gets only 1/1,000,000,000 of energy from the sun, mostly as infrared and visible light </li></ul><ul><li>Energy cannot be created nor destroyed, but it can change form, and so solar energy can be converted into heat ( or thermal) energy, electricity, </li></ul><ul><li>It can replace fossil fuels, biomass fuels and nuclear in some areas </li></ul>
  5. 5. Advantages of Solar <ul><li>Clean- nonpolluting </li></ul><ul><li>Free </li></ul><ul><li>Cost can be recovered in reduced fuel costs </li></ul>
  6. 6. Disadvantage <ul><li>Not steady- must live in a sunny area </li></ul><ul><li>Devices for storing solar energy need to be improved </li></ul><ul><li>Size of collectors and cost may be prohibitive </li></ul>
  7. 7. Passive Solar <ul><li>Sun’s energy is collected, stored and distributed naturally in an enclosed dwelling </li></ul><ul><li>Examples: greenhouse, car on sunny day </li></ul><ul><li>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 </li></ul>
  8. 8. Active Solar Energy <ul><li>Devices are used to collect, store and circulate heat from the sun </li></ul><ul><li>Uses tubes, tanks, pumps, fluids, fans </li></ul><ul><li>Solar collectors collect the sun’s energy- usually placed on a roof- called flat-plate collectors </li></ul><ul><li>Flat-plate collectors are painted black, and have system of tubes filled with fluid (water, antifreeze or air). Look at pg 268 </li></ul>
  9. 9. <ul><li>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 </li></ul><ul><li>Used in Israel, Japan, India and West Indies- can be cost effective </li></ul><ul><li>Read about Solar One ( pg 268) </li></ul>
  10. 10. Photovoltaic Cells <ul><li>The photovoltaic cell takes the sun’s energy and converts it directly into electricity (PV cell) </li></ul><ul><li>PV cell is a thin wafer made of semiconductors ( Si, Se) </li></ul><ul><li>Electrons move from one wafer to another when sun’s rays strike the semiconductor. </li></ul><ul><li>Movement of electrons is electricity </li></ul><ul><li>PV cells- found in calculators, watches, satellites use them </li></ul><ul><li>Engineers working on solar powered cars </li></ul>

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