Array Sizing

fireflyfirefly Solar Expert Posts: 66 ✭✭
Can anyone tell me if there is an array sizing tool out there, where you can mix and match various panels.


  • mike95490mike95490 Solar Expert Posts: 8,067 ✭✭✭✭✭
    Re: Array Sizing

    I think most will assume one size.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
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    gen: ,

  • BB.BB. Super Moderators, Administrators Posts: 28,315 admin
    Re: Array Sizing

    Not really... However, I find the Xantrex String Sizing tool to be very handy.

    Just pick any Xantrex GT inverter (default is fine), and then you can display virtually any past or present solar panel specification (all in common format/units) that was/is on the market.

    Also, you can play with calculator to set min/max temperatures, and, what I do, is take (for example) the Min/Max voltages calculated (Vmp hot, Voc cold) for a string (say 8 panels), and simply divide by string size (say 8 panels) to find the corrected specifications for 1 panel.

    Sounds like a lot of work, but, in reality, it is a lot easier than hunting around and reading every spec. sheet out there.

    Once you have some candidates, then you can find the specs. for those couple of panels and confirm the numbers (always a good idea before spending $$$ on something that may not work).

    Some other vendors out there also offer their version of string calculators for their controllers/inverters. I have not found any errors in the Xantrex calculations--but I have seen major errors in some other vendors (i.e., if you follow their results, the system will not function).

    As far as I know, you will not find any sizing tool out there that would let you mix/match panels...

    Normally, this should not be a huge issue--basically, if you match STC rated current (Imp) for series strings, or match Vmp for parallel strings (same number of solar cells per panel--i.e., 32 or 36 cells per panel, and assuming that the panels are the same technology family--all Mono/Poly Crystalline sets, or all Amorphous panel sets)--you should be OK.

    You could help by building a spread sheet that adds voltage and currents so you can quickly check a configuration with differing panels.

    My 2 cents worth... If anyone has better links--let us know.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • EcnerwalEcnerwal Solar Expert Posts: 101 ✭✭
    Re: Array Sizing

    Basically, if you are trying to grow upon your already mixed set of panels, you have a couple of options - one is to do the dance of trying to match Imp for series, the other is to try to match Vmp for parallel.

    Another option is to put different sets on different charge controllers to isolate wildly different panel characteristics. Can be somewhat costly if you have a controller with lots of headroom. On the other hand, if your added panels will be enough to fill a controller, just leave the old ones and put the new panels on a new controller.

    A third is to either sell off the old panels, or change their job - ie, if you can set your old panels to running a water pump into a large tank, with no battery involved, that can be a win if water pumping is a significant part of your power use.
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