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Hi and Help

  1. Apr 24, 2008 #1
    Im trying to get to grips with factors? and want to check my methodology, so:

    It all about solar panels..I've calculated how much power the cell will produced @ AM1.5 this is 73 mW cm-2 .

    Now my question is, i have to calculate the short fall by a factor of 1000 due when its used indoors for example. So am i right saying:

    73 mW cm^-2
    / 1000

    = 7.3^-3 mW cm^-2

    - 73 mW cm^-2

    = 65.7 mW cm^-2 (is this the shortfall answer)

    Any help would be appreciated. and if you have any subsequent Q's, il try and answer them
     
  2. jcsd
  3. Apr 26, 2008 #2
    i can't believe nobody can help!
     
  4. Apr 26, 2008 #3

    tiny-tim

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    Welcome to PF!

    Hi Tevion! Welcome to PF! :smile:

    If by shortfall you mean a decrease of 1/10, or 0.1, it's probably easier, instead of multiplying by that factor and then subtracting, to multiply by (1 - the factor), in this case (1 - 0.1), = 0.9.

    So, having worked out the factor, just say:

    73 mW cm-2 x 0.9 = 65.7 mW cm-2.​

    Or if you mean a decrease of 1/1000, or .001, it's

    73 mW cm-2 x 0.999 = 72.927 mW cm-2. :smile:
     
  5. Apr 26, 2008 #4
    So can you clarify how to deduce

    7.3^-3 mW cm^-2

    by a factor of 1000.

    Thanks Tim
     
  6. Apr 26, 2008 #5

    tiny-tim

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    Hi Tevion! :smile:

    I'm honestly not sure what you mean.

    Do you mean reducing it by one part in 1000, or to one part in 1000?

    You were orignally talking about the efficicency of solar panels indoors, and a reduction of 1/1000 seems far too small, while a reduction to 1/1000 seems far too large. :confused:

    Anyway, starting with 7.3, a reduction by 1/1000 would be 7.2927 (or 7.29 approx), while a reduction to 1/1000 would be .0073. :smile:

    What is it about factors that's worrying you? :smile:
     
  7. Apr 26, 2008 #6

    tiny-tim

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    Hi Tevion! :smile:

    Thanks for the PM.
    Well, it seems a slightly strange way of putting it (I would say "a factor of 1/1000", not "a factor of 1000" :frown: ) … but I'd say they mean 0.999 x 73. :smile:
     
  8. Apr 28, 2008 #7
    I still dont quite understand it, how did you arrive @ the 0.999?

    Im about to send you a PM :)
     
  9. Apr 28, 2008 #8

    tiny-tim

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    1 - 1/1000. :smile:

    (oh please don't send me PMs … I never answer them! :smile:)
     
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