Vmpp Question

icarus
icarus Solar Expert Posts: 5,436 ✭✭✭✭
in Off Grid Solar & Battery Systems #1
Two questions,,

First, has anyone had any experience with the "Sun Modules" sold by: http://www.sunelec.com/ They seem to be the same as Evergreen's but without the UL label.

Second,, How far apart can different panels be with Vmppt and be wired into a parallel string with a conventional controller, or a 12volt Mppt Controller like the BlueSky 2512 series. I am considering adding a couple to my string(s) and wonder how right on I need to be. What are the consequences of having panels that are significantly out of range?

Thanks,

Tony
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Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,650 admin
    #2
    Re: Vmpp Question

    At least according to Fronius (their White Paper PDF file download), the power of two dissimilar strings will, basically add up to the P=I*V where I is the sum of the currents, and Vmp will be the voltage of the string with the lower Vmp.

    I presume that it is possible different MPPT algorithims from other vendors may end up finding different Vmp Peaks... Also probably depends on how far apart the Vmp and Imp values are (a string with low Vmp and high Imp vs a string with high Vmp and lower Imp--which will the controller settle on? Don't have a clue).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #3
    Re: Vmpp Question

    Bill,

    Thanks,
    So in that regard, if I have one panel with a Vpm of say 17.4 and another of 17.8 , both with Imp of say 3 amps, I would then get ~ 6 amp @ 17.4v or ~104.4 watts as opposed to 106.8 watts?

    Doesn't sound like enough of a loss to even worry about in a small array,

    Tony
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,650 admin
    #4
    Re: Vmpp Question

    Yep. ;)

    -Bill

    PS: Add filler of 18 characters (prevents pithy replies) :roll:
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • n3qik
    n3qik Solar Expert Posts: 741 ✭✭
    #5
    Re: Vmpp Question

    I have 2 arrays pointing in two different directions tied to the same C60 CC. One is 8 Unisolar 64W panels and the other is 7 Unisolar 62W panels. During the summer, I am at 80% of rated power with 10% looses due to the long wire run to shed. So with a PWM charger I see no losses with mixed matched panels. Now with a MPPT controller this may not hold true.
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  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    #6
    Re: Vmpp Question

    Evergreen vs. Sun modules: http://sunelec.com//index.php?main_page=compare

    HTH,
    Jim / crewzer
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #7
    Re: Vmpp Question

    Jim,

    I found the same link,,, but no real information. Are these panels built by Evergreen, or are they some knock off? Has anyone ever used them, and with what success?

    Tony
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  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    #8
    Re: Vmpp Question

    Tony,

    I have no direct experience with 'em. I seem to recall that Solar Guppy / Henry C. has had favorable experience... See this link for one of his comments:

    http://forum.solar-electric.com/showthread.php?p=16223&highlight=evergreen+sun+factory#post16223

    HTH,
    Jim / crewzer
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #9
    Re: Vmpp Question

    As always,,,Thanks Jim,
    It's nice to see some real world experience.

    Tony
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  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    #10
    Re: Vmpp Question

    I have some Sun Modules, they are manufactured in Germany By Evergreen as Evergreen panels, but due to cosmetic defects, Evergreen had made a deal with SunElec to label them as Suns without the UL label to maximize manufacturing efficiency.

    They ARE Evergreens in every way except for a sticker .. Even with the minor defects ( most were slik screen wave like distortion on the some cells ) they have the -2%/+4% power warranty and are excellent performing panels

    From a cost/watt value, they is no better offering for true Si panels .. just keep in mind they don't have a UL label, so for applications that need that, go with the Evergreen "B" stock for about 40 cents more a watt
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #11
    Re: Vmpp Question

    Thanks, SG,

    Tony
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