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calculating loses

Discussion in 'Photovoltaics' started by David Lesher, Jul 16, 2010.

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  1. David Lesher

    David Lesher Guest

    So I have a demand of 1.6 KWh/day, and insolation is 5.5 kwh/M^2day.

    If the world was perfect, I'd just divide to get panel area.

    It's not, so I assume there are other factors I must
    include; the panel efficiency of course, and some electrical
    losses. [It's a DC pump motor, so that eliminates one,
    conversion losses..]

    Where do I go for more data on this aspect?
     
  2. David Lesher

    David Lesher Guest

    {STC vs PTC, temp derate, aging}

    Thanks. I was also hoping for some writeups on how much each
    factor deserves, etc.
    ....
    And unlike one vender's bid: by keeping the supply voltage up.
    [The SqFlex series will run from 30-300V, and run well above 120V.]
    Nope, we're storing energy the rational way: Ug = mgh
    No oxides of lead or such needed, and very low losses.
    We shall all wear out before G*{m_1*m_2}/{r^2} does.
    I figure we have 40-60 DAYS worth of water storage, so a few
    cloudy days won't cause grief.

    Further, there's some balancing factors. Rainy season has less
    sun, but the well level will likely be 75-125 ft higher, using
    less power. And the panels will be cooler.
    Well, I've got a handle on everything save the panel issues.
    Thanks for your help.
     
  3. Include Panel dust too.

    I believe the efficiency turns out to be somwhere around 75% of the
    advertised panel power.
    72% if you want to be exact for a grid tie.

    I think someone here , with the same question, was seeing values in this
    range.

    cheers
     
  4. Include Panel dust too.

    I believe the efficiency turns out to be somwhere around 75% of the
    advertised panel power.
    72% if you want to be exact for a grid tie.

    I think someone here , with the same question, was seeing values in this
    range.

    cheers
     
  5. Panel dust and atmospheric dust (eg dirt, smog) has an effect. Depends
    upon location as to the amount. I have some info somewhere, if I
    remember correctly its in the 3% range.

    Something associated with Global Dimming ;) 1Kwm some think is
    unrealistic. And conservativly use 800wm instead.

    I have some info somewhere, I'll try to dig it up tonight, got something
    to do before this heavy wall of rain hits NY.


    Cheers
     
  6. I have notes that indicate 900wm^2 is a realistic value to use in
    calculations.
    Inverter effeciency 94%
    Wiring loss 2%
    Dust and wire connections 10% loss.

    ..9 x .94 x. 98 x .9 = 74.6% system efficiency.

    Cheers
     
  7. The PVwatts system is a good system, heres a list of derating factors.
    <http://www.nrel.gov/rredc/pvwatts/changing_parameters.html>

    Dust, or Soiling (as it is listed) Does vary with location.

    But generally, the system efficiency is ~75%

    Cheers
     
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