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Measure Daily Output of a Solar Panel

Discussion in 'Renewable Energy' started by Moneer81, Sep 28, 2008.

  1. Mike_2545

    Mike_2545 Super Moderator

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    Yes, and there is work being done to get an 80% efficient panel that will even work at night, capturing infa-red radiation.
     
  2. be80be

    be80be Well-Known Member

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    What I have seen for about $800.00 you can get what they call 60% efficient it's a 3x5 foot But I would say efficient is a big word with solar panels. What do you do when it rains
    for 2 days.
     
  3. duffy

    duffy New Member

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    Not 60%. Efficiency has nothing to do with rain.
     
  4. dave

    Dave New Member

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  5. Mike_2545

    Mike_2545 Super Moderator

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    Please post the source... I would like to look at that!
     
  6. be80be

    be80be Well-Known Member

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    I no that was a joke. I can't see Efficiency of a solar cell I made this 1 and it can put out this you made 1 and it puts out more then mind did. They work by light and I know there not tested in the same. Light I think this is where you would see what people are saying to get the best
     
  7. Willbe

    Willbe New Member

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    No, I mean how much of the available irradiance can be converted at all. The 12% efficiency then works only on that. Maybe solar panels only convert visible light, I dunno'.

    For a long time I thought only 60w per square foot was available. 12% of 60 would then be 7w.

    Not the best link that addresses this issue\/
    Science Fair Project Idea: Wavelength of light that hits a solar panel

    but "bandwidth" (of solar panels) doesn't seem to get good hits either.

    This graph shows energy vs. wavelength.
    File:Solar Spectrum.png - Wikipedia, the free encyclopedia
    Now if we had the "freq. response" of solar panels we all should be able to calculate all of this.
     
    Last edited: Mar 1, 2009
  8. be80be

    be80be Well-Known Member

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  9. Mike_2545

    Mike_2545 Super Moderator

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    It says "60 High-Efficiency Solar Cells" Not 60% efficient...

    Easy mistake
     
  10. umer27

    umer27 New Member

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    Solar cells have a 22 % efficiency at max .. this is the latest technology Im talking about..

    your garden solar panel has 6%
    Poly crsytalline is about 14 %
    Mono is 16%


    The efficiency here means that the solar panel converts this much % of actual energy falling on it into electricity !

    :)
     
  11. Willbe

    Willbe New Member

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    6% of the energy from 300 nm to 2500 nm wavelengths, or 6% of only the visible light energy (400 to 700 nm)?
     
  12. Mike_2545

    Mike_2545 Super Moderator

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    I think it's the % of photons striking the surface of the panel.
     
    Last edited: Mar 1, 2009
  13. duffy

    duffy New Member

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    Come on guys - we're engineers. There's a standard for this. It's ASTM G 173-03 -
    "STC specifies a temperature of 25°C and an irradiance of 1000 W/m2 with an air mass 1.5 (AM1.5) spectrum. These correspond to the irradiance and spectrum of sunlight incident on a clear day upon a sun-facing 37°-tilted surface with the sun at an angle of 41.81° above the horizon."
     
  14. umer27

    umer27 New Member

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    Im almost an engineer (being in my final semester) .. who else is an engineer ?
     
  15. Willbe

    Willbe New Member

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    So 60w for a one meter sq. panel.
    By running water through a flat black pipe at the focus of a parabolic mirror you could probably get almost the whole kW.
     
    Last edited: Mar 1, 2009
  16. duffy

    duffy New Member

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    Maybe if you have a perfect black-body absorber in a Dewar flask you could. A practical system is going to be lower, but would still probably absorb more of the energy than a solar cell.

    Problem is, it's thermal energy. By the time you get it into electricity you are going to suffer serious conversion efficiencies. I don't think any steam turbine ever broke 50% efficiency. If your solar collector is 60% efficient, the steam turbine is 40% efficient, the generator is 80% efficient, you know, 60% x 40% x 80% = 19%
     
    Last edited: Mar 1, 2009
  17. Oznog

    Oznog Active Member

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    Look up "Solar Insolence" for your location.
    There are parameters available to calculate how much energy can be produced by the "Standard" of 1000W/M^2 averaged over a year for flat-on-ground plate, fixed-tilt plates, and tracking plates.

    For Austin, Tx the average daily insolence for a fixed-tilt plate was about 4.5 kwh/m^2/day, averaged over a whole year. This figure accounts for night, seasons, dust in the air, and weather. It does not account for tree shading or dirt on the panels. Say I installed a 3KW solar system. I don't know exactly what the surface area is, but I don't need to know. The rating means that 1KW/M^2=3KW output for the array, and 0.5KW/M^2 late in the day means 1.5KW out.

    I get 4.5 "standard" hours worth of sun on a fixed-tilt panel tilted at an ideal angle. The 3KW rating comes from a "standard" 1KW/M^2 irradiance. So it's 13.5KWH/day output, averaged over a year. Or 4,927.5 KWH/yr total.

    However, the panel output goes down substantially with elevated temp, and the standard cell rating method is for 25C, which isn't applicable to most installations. Almost no installations have any measures to cool the cells inside sealed panels. We're a lot hotter during the most productive hours. This can easily reduce the total average output by 20% or more.

    The extra energy gained by using a "tracker" is not all that great considering the cost of "moving mounting systems". It could easily cost 2x or more what a fixed system costs, but won't put out 2x more power. This would generally mean it's more cost-effective to add 2x as many panels as opposed to tracking.

    There is some seasonal benefit to pointing the panels lower towards the horizon in winter, as the sun is lower then. It's lower cost anyways than a mechnical east-west tracker, and no significant breakdown issues, but still you're going up there on the roof, maybe spending an hour or two, rebolting the mounts' tilt angle for a few $ worth of power over the course of the season.

    SO... you may want to create a test jig capable of measuring power output under some sort of "standard" 1KW/M^2 light source to characterize them, if you don't have mfg specs. But the daily output figure, over a year, is much easier to get, and much more accurate, from external data sources. Your data will be full of data confusion from panel dust, temp, seasons (if you don't keep it up for a year), etc.
     
    Last edited: Jul 5, 2009

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