uneven sun on panel strings effect on controller

WaterWheelWaterWheel Registered Users Posts: 340 ✭✭✭
edited May 2017 in Solar Beginners Corner #1
I currently have one large ground mount  and am looking to add a few panels using the roof.     One section of roof faces SSE with 100% sun exposure until 4 pm so it can give me more early energy but this can only hold 1 string of 3 panels.        The other section of roof faces WSW with great sun exposure after 10:30 am until sunset and also can only hold 1 string of 3 panels.

My current controller (Conext 80-600) is maxed out and not a good choice for short relatively low voltage strings so I was going to add a Conext 60-150 controller.      This will allow the controllers to communicate over the Xanbus.        I understand that having these panels face more east and west will reduce efficiency but it's a price I'm willing to pay for the ease of mounting and reducing battery usage through a longer solar day with the panel's east and west orientation.    

My question is how badly is the different angles these panels will be facing going to affect the controller?       If say before 10:30am and only the east panels are getting sunshine is the lack of power from the west facing panels going to seriously hurt controller output?       How about when one string of panels is getting good sun but the other set is barely getting sun and barely putting out power?

Conext XW6848 with PDP, SCP, 80/600 controller, 60/150 controller and Conext battery monitor

21 SW280 panels on Schletter ground mount

48v Rolls 6CS 27P

Comments

  • animattanimatt Solar Expert Posts: 295 ✭✭✭
    edited May 2017 #2
    It should work at well for your purposed design 

    It may not hit exact power max from both strings at the same time. But not a big deal.


    Not sure if you are off grid. If so I believe most would suggest your purposed upgrade is very benificial.   Spreading solar input out across the day. It is letting your batteries stay more fully charged until later in the evening, and also begins charging earlier. Petext for batteries.


    Shade and different light exposure really seems to be a big deal if it varies inside a string. Shading one panel in a string basically degrades output of entire string.

    But if only variation is between parallel strings not a big deal. 

  • Dave AngeliniDave Angelini Solar Expert Posts: 6,028 ✭✭✭✭✭
    The -80 controller is designed to be shade tolerant in its MPPT. The -60 is not. I would just set one up and add a second controller if I noticed weird power fluctuations. When I have done this in the past it was usually caused by clouds messing up the MPV.  Run your wiring to allow adding a second controller or at least plan for it. How are the water wheels doing?
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • EstragonEstragon Registered Users Posts: 4,495 ✭✭✭✭✭
    Dave - I'm curious how the controller deals with the orientations. Wouldn't it have a problem finding a mppt?
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • Dave AngeliniDave Angelini Solar Expert Posts: 6,028 ✭✭✭✭✭
    Rephrase your question please? As Animatt says some of this is just parallel strings. One way to test this just loading and running 1500 watt toaster oven cycling. You want the other loads to be close to what your PV max power is with the toaster oven cycled on. As the oven cycles does the Battery voltage hold up and is the CC repeatable at picking the correct MPV?  Add in some clouds!

    I have seen this negative effect and I am a believer of running 2 mppt's if this is important enough. As it turns out, it usually is a good thing to do in large systems offgrid in winter, everything must be right to avoid or minimize needing a generator.






    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • EstragonEstragon Registered Users Posts: 4,495 ✭✭✭✭✭
    You mentioned the 80 being shade tolerant versus the 60 not. In the context of the question, an east and a west string in parallel, I was wondering what it is about the 80 that helps vs the 60.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • Dave AngeliniDave Angelini Solar Expert Posts: 6,028 ✭✭✭✭✭
    The -80 is a 2012 design and has the memory to run an algorithm to keep track of various power points and not get stuck on one that produces less power. The -60 is from 2006 and can't keep track as well. They both are very fast but if I was adding power the cost is pretty low to do it right. There is a White paper on the Schneider site on shade tolerance that came out during beta testing.
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • EstragonEstragon Registered Users Posts: 4,495 ✭✭✭✭✭
    That makes sense. Thanks
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • WaterWheelWaterWheel Registered Users Posts: 340 ✭✭✭
    Dave,     The water wheel business is booming and I'm ready for a day off.       Thanks for asking and your info on the 60 being less able to deal with shading.       I'll wire in such a way that I can add another controller if I see the west facing panels not adding good power as the east facing panels begin to shade.

    Conext XW6848 with PDP, SCP, 80/600 controller, 60/150 controller and Conext battery monitor

    21 SW280 panels on Schletter ground mount

    48v Rolls 6CS 27P

  • Dave AngeliniDave Angelini Solar Expert Posts: 6,028 ✭✭✭✭✭
    Well it is Memorial Day weekend!  All gave some, and some gave all  :'(

    The toaster oven test is a good one (or similar cycling loads). On your system all you have to do is get an SD card and it can log the power every 5 seconds. You could also log the MPV during the day. Combox will do this for years on a small SD.

    Water wheels don't do well out here. We just drain it into the ocean and screw the Farmers. I am not sure most Californian know where the food at the grocery store comes from. Excellent documentary on PBS called "Tapped Out" 
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

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