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Compatibility of solar panels / grid-tie inverters

Discussion in 'Renewable Energy' started by Jules_Theone, Mar 30, 2013.

  1. Jules_Theone

    Jules_Theone Member

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    Location:
    Exeter, England
    Hi,

    I have convinced my father to get solar panels fitted to his house roof, I have already had a 4kWp grid-tied system fitted to mine nearly a year back and it seems to be going well for me. He has had a couple of quotes from different companies but only one has given an actual written quote with datasheets etc.

    His roof is quite complicated as it doesn't have much space facing south, some east and some west so I believe there will be solar panels facing all three directions. This complicates MPP I guess.

    The quote will the most detail is:

    2kWp:
    8 x 250W Yingli YL250 panels
    2000HF SMA Sunnyboy Inverter
    Cable / connectors etc.

    I was looking closely at if the inverter will work with the solar panels - comparing the specs, voltages / current etc and it doesn't look to me that it will work all that well.

    250W Yingli Panels:
    http://www.solardesigntool.com/components/module-panel-solar/Yingli-Solar/1170/YL250C-30b/specification-data-sheet.html
    Pmax = 250W (8 x 250 = 2000W)
    Vmpp = 30.5V (8 x 30.5 = 244V)
    Impp = 8.2A (series connected so 8 panels = 8.2A)
    Voc = 38.1V (8 x 38.1 = 304.8V)

    2000HF SMA Inverter:
    http://www.rexelrenewableenergy.co.uk/FileDepository/TechDocs/Inverters/SMA%20Sunnyboy%20Installation%20Guide%202000HF%202500HF%203000HF.pdf
    Vmpp = 175V - 560V
    Vstart = 220V
    Number of independent MPP = 1
    Number of strings per MPP = 2

    I think it will not work very well if some panels are facing west, some east and some south if they are all in series. And even then the MPP voltage of 8 panels in series is not much more than the startup voltage for the inverter.
    Ideally the system should have separate MPP tracking (separate inverters?) for each set of panels facing different directions. Due to roof space, I think I can fit 4 facing west, 2 facing south and 2 facing east.

    Does anyone have any recommendations to the setup because I might just end up doing it myself.

    Thanks for any help,

    Jules
     
  2. KeepItSimpleStupid

    KeepItSimpleStupid Well-Known Member Most Helpful Member

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    Vstart could be a major issue. I troubleshot an early installation of solar panels like 1980's or so. Everyone was wondering why the system never worked right. Voc was actually larger than the startup voltage at times.

    Multiple inverters might make sense.
     
  3. nsaspook

    nsaspook Well-Known Member

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  4. dave

    Dave New Member

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  5. extreampv

    extreampv New Member

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    If your roof space is broken up / more complicated than a string inverter with a single MPPT input has (the SB2000HF is SINGLE MPPT) then I would suggest micro inverters:
    http://www.cclcomponents.com/product.asp?ID=3279

    If your roof was a simple installation with all panels pointing in the same direction then the SB2000HF would work. The vstart voltage isn't really an issue for your installation, more the face that from the sound of it your panels are pointing different directions and/or some shading. In this case on a larger system a dual MPPT inverter would help, but at 2kw only single trackers are available. Separate string inverters arnt' a good idea as they would struggle to start with only 4 panels.
    In this case micro inverters do help. You could also consider using higher power panels - something like SolarWorld 270W. You would gain in extra yield over the lifetime of the system.

    Ken
     

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