Power output with PV SOL

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JavierOL
JavierOL Solar Expert Posts: 27
Hello!

I am calculating the power output of an existing PV system with the formula below:

Pg=Pgfv*(G/Gstc)*[1-(YPm*(Tc-Tstc))]

This is the typical formula used to calculate the output power. My problem is that I need to check if this formula is the right one for my system, and for this I am using PVSOL. The results don't match, and I am using the same values for irradiance and Temperature.

Anyone know wich formula use PV SOL to calculate the output power?

Thank you!

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  • BB.
    BB. Super Moderators, Administrators Posts: 33,497 admin
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    Re: Power output with PV SOL

    Take out the G/Gstc

    NOTE: I Got the G/Gstc wrong... Ignore.

    That is the generic hot panel setting, and is upside down.

    Pvfg should be the array marketing specification.

    And multiply by around 0.95 for MPPT controller derating.

    If this is a PWM controller, then all of this is wrong.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BB.
    BB. Super Moderators, Administrators Posts: 33,497 admin
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    Re: Power output with PV SOL

    Tc is actual cell temp in degree C And may be 10-30 C above ambient temperatures.<br><br>Tstc should be 25C.<br><br>Forgive typing mistakes... Using phone.<br><br>-
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • JavierOL
    JavierOL Solar Expert Posts: 27
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    Re: Power output with PV SOL

    Hi,

    I know what the factors mean, but why should I remove the G/Gstc factor?

    I realize that I made a mistake, the temperature factor should be like this: [1+(YPm*(Tc-Tstc))], where YPm is the variation coefficient of the power with the module temperature.

    Anyway my doubt is if PVSOL use the same formula to calculate the output power or not... the results don't match...
  • BB.
    BB. Super Moderators, Administrators Posts: 33,497 admin
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    Re: Power output with PV SOL

    What exactly is "G"?

    And I made a mistake. I was thinking Gptc which is temperature corrected.

    So what is G vs Pgfv?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BB.
    BB. Super Moderators, Administrators Posts: 33,497 admin
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    Re: Power output with PV SOL

    And the temperature correction now has the wrong sign... I think.

    When Tcell goes below 25C or Tstc, you want the power output to increase.

    Sorry for any mistakes.... Doing this on a 2" Phone screen.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • JavierOL
    JavierOL Solar Expert Posts: 27
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    Re: Power output with PV SOL

    G is the Global irradiance that reach to the modules, and Pgfv is the maximum power of the module in STC (nominal power)
  • BB.
    BB. Super Moderators, Administrators Posts: 33,497 admin
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    Re: Power output with PV SOL

    Ok with g/gstc.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • JavierOL
    JavierOL Solar Expert Posts: 27
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    Re: Power output with PV SOL

    ok, but could you confim me if the temperature factor is [1+(YPm*(Tc-Tstc))] or [1-(YPm*(Tc-Tstc))]??

    I am not sure at all..
  • ggunn
    ggunn Solar Expert Posts: 1,973 ✭✭✭
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    Re: Power output with PV SOL
    JavierOL wrote: »
    ok, but could you confim me if the temperature factor is [1+(YPm*(Tc-Tstc))] or [1-(YPm*(Tc-Tstc))]??

    I am not sure at all..
    Run some test numbers and verify it for yourself; power goes down as temperature increases.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,497 admin
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    Re: Power output with PV SOL

    Second equation should be correct. Minus times negative adds to the output.

    -Bill

    PS: If you want, can you type out the values you are using?

    -BB
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset