Fronius Galvo GTI (1.5KW) - Why is there 3 MPPT Inputs?

fooliosfoolios Solar Expert Posts: 53 ✭✭
Why is there so many DC inputs on these inverters?
The nominal voltage is 260v at 1500 watts. Nominal, I take it, is the voltage we want to aim for for the best efficiency of the inverter.
Even with 12 volt panels, it would take 20 panels in series to get to that voltage. All of those panels in series will only need one input. That will be 2000 watts of which the inverter can support but will still only deliver a max of 1500 watts.
I think that's the worse case scenario so I don't understand why so many inputs are available to be used.
If I go with a larger volt panel or series of panels for example; 36 volts: 260v/36v= 7 panels in a string and easily fills up the 2000 watts from one string.
I don't see a ratio that would require the use of all the inputs.
If I have 14x12 volt panels that make up ~1500 watts, I can not separate them into different strings to achieve the nominal voltage.
This has me confused.
Can someone please explain why there are three inputs? Is it for stringing together more of these GTI's? But I think there are separate modules for that kind of thing. Not sure about the Fronius brand.

Is it possible to use 12v and/or 24 volt panels with it?

Comments

  • PhotowhitPhotowhit Solar Expert Posts: 5,409 ✭✭✭✭✭

    Well for you it's not needed, but if you had some tthin film panels which tend to have high voltage and lower wattage you might need all three!

    Here are some 100 watt panels with a vmp of 75 volts;

    http://www.diytrade.com/china/pd/6560765/Thin_Film_Solar_Panel_100W.html

    The inverter doesn't care what type or voltage panels you connect, so long as the string voltage and amperage is in it's range.

    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, 660 ah 24v ForkLift battery. Off grid for @16 of last 17 years. Assorted other systems, and to many panels in the closet to not do more...lol
  • Dave AngeliniDave Angelini Solar Expert Posts: 5,550 ✭✭✭✭✭
    It is there for multiple arrays plain and simple. A secondary is shading but that should always be avoided.
     I would guess Sunpower solar panels changed the world with much higher Vmp's.
    Most panels now are 300 watts at 36 to 60V nominal. For offgrid dual mppt's and an east west array are the cats meow!
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • fooliosfoolios Solar Expert Posts: 53 ✭✭
    Wow 60 and 75 volt panels. OK, thanks for the Info! 
    East and west facing arrays. Wow, that's gonna take a lot of dough. 
    So what I could do is add one of those 60 or 75 watt panels into my string to boost its voltage.
    14x12v =168v, then add 1x75v and I'Ll have nearly the nominal voltage. 
    That's very helpful info. This will allow me to use the panels I already have.
  • Dave AngeliniDave Angelini Solar Expert Posts: 5,550 ✭✭✭✭✭
    It is not inexpensive to do this right and I get it!
     Most of the people I know do not have the time to slowly grow and make all the mistakes or do things over and over.
    Good Luck to you!
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • littleharbor2littleharbor2 Solar Expert Posts: 1,569 ✭✭✭✭
    Check the amperage of those high volt thin film panels. Typically pretty low. The only way to incorporate one into your strings is have one with similar amperage rating as your 12 volt panels otherwise it will drag the whole string down to it's amperage and seriously affect your output.

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric, 700 ah @24 volt AGM battery bank. Plenty of Baja Sea of Cortez sunshine.

  • fooliosfoolios Solar Expert Posts: 53 ✭✭
    Thanks for that valuable input.
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