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Solar panel output variation- Is this within the range of normal?

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  • Solar panel output variation- Is this within the range of normal?

    Hi everyone,

    I am the excited about my new solar install, but am concerned about how variable the ouput is between panels. I have a 12.16kw system with a 7.7kw solaredge HD Wave inverter. The system uses optimizers, is facing 282 degrees on a 22 degree angle roof. The only shadows would be from a large chimney, but no trees.

    Could I have a malfunctioning solarpanel or two?





    Attached Files

  • #2
    Originally posted by Spectrum1c View Post
    Hi everyone,

    I am the excited about my new solar install, but am concerned about how variable the ouput is between panels. I have a 12.16kw system with a 7.7kw solaredge HD Wave inverter. The system uses optimizers, is facing 282 degrees on a 22 degree angle roof. The only shadows would be from a large chimney, but no trees.

    Could I have a malfunctioning solarpanel or two?
    Why do you have such a small inverter?

    Your optimizers are cutting power to some modules to limit the power to the inverter .
    OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

    Comment


    • #3
      Screenshot_20180511-185923_SolarEdge.jpg
      QUOTE=ButchDeal;n376612]

      Why do you have such a small inverter?

      Your optimizers are cutting power to some modules to limit the power to the inverter .[/QUOTE]

      Thanks for the reply ButchDeal.

      I believe because my orientation is not ideal and Massachussetts supposedly gives you a hard time with an inverter greater than 10kw.

      Given that my system is expected to experience serious clipping, I'm surprised that I a have dips in my output. Today was a little cloudy, but not dark overcast. However my output dipped in the middle of day:


      Does this all look normal to you?
      Attached Files

      Comment


      • #4
        Originally posted by Spectrum1c View Post

        I believe because my orientation is not ideal and Massachussetts supposedly gives you a hard time with an inverter greater than 10kw.

        Given that my system is expected to experience serious clipping, I'm surprised that I a have dips in my output. Today was a little cloudy, but not dark overcast. However my output dipped in the middle of day:


        Does this all look normal to you?
        So your array is south west facing that just moves the peak later in the day, not reducing the peak.
        You could have easily installed the SE10000h inverter which is 10kw instead of a 7.6kw.

        clouds are the dips in production. Clipping is causing the optimizers to cut production in different panels to limit output though.
        OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

        Comment


        • #5
          Wouldn't 282 degrees be more West-Northwest?
          2.2kw Suntech mono, Classic 200, NEW Trace SW4024

          Comment


          • #6
            Originally posted by ButchDeal View Post

            So your array is south west facing that just moves the peak later in the day, not reducing the peak.
            You could have easily installed the SE10000h inverter which is 10kw instead of a 7.6kw.

            clouds are the dips in production. Clipping is causing the optimizers to cut production in different panels to limit output though.
            Unfortunately my panels face northwest . Pvwatts estimates me losing on 500w/yr. I guess I should have pushed for a larger inverter, but at the time i needed someone who could get me under the recently expired Massachusetts srec2 system and every installer was completely maxed out on installs.

            ​​​​​​Thanks for the replies ButchDeal. So it seems the system functioning appropriately for it's design?

            Comment


            • #7
              Originally posted by Spectrum1c View Post

              Unfortunately my panels face northwest . Pvwatts estimates me losing on 500w/yr. I guess I should have pushed for a larger inverter, but at the time i needed someone who could get me under the recently expired Massachusetts srec2 system and every installer was completely maxed out on installs.

              Thanks for the replies ButchDeal. So it seems the system functioning appropriately for it's design?
              It is much closer to west than to north west ( 12 degrees from west) and is that magnetic or true?
              500w/yr does not make since, it should be in kWh not watts or kw....

              yes it is working as designed, the installer not so much. You can see a little over 4 hours of clipping.

              OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

              Comment


              • #8
                Originally posted by littleharbor View Post
                Wouldn't 282 degrees be more West-Northwest?
                yes my mistake west by north west though I suspect that this is magnetic not true azimuth.
                OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

                Comment


                • #9
                  Originally posted by ButchDeal View Post

                  yes my mistake west by north west though I suspect that this is magnetic not true azimuth.
                  Looks like Magnetic declination would be about 15 degrees in Mass.
                  2.2kw Suntech mono, Classic 200, NEW Trace SW4024

                  Comment


                  • #10
                    Yes, it's 282 magnetic north, not true north. I tried to calculate what that would be in true north, but couldn't figure it out. Would the 15 degree declination make it 296 or 258 true north?
                    ButchDeal, I misspoke on the watts. Pvwatts estimated 500kw/hr difference over the year.
                    Thanks all for your responses.
                    Last edited by Spectrum1c; 05-11-2018, 11:22 PM.

                    Comment


                    • #11
                      Originally posted by Spectrum1c View Post
                      Yes, it's 282 magnetic north, not true north. I tried to calculate what that would be in true north, but couldn't figure it out. Would the 15 degree declination make it 296 or 258 true north?
                      ButchDeal, I misspoke on the watts. Pvwatts estimated 500kw/hr difference over the year.
                      Thanks all for your responses.
                      Subtract it, so your modules are facing almost west.
                      Most smart phones also have a setting to set the compas to true or magnetic...

                      how much is is that 1/2MWh/year to yu from the poco, it looks like a half an SREC is worth at least $130 per year. That
                      OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

                      Comment


                      • #12
                        Seems reasonable given the large chimney. That will cut the panels around it a good amount.

                        Also, the 7.7kw is an installers favorite because it requires a 40amp breaker with 38.5 amps of calculated protection.. (7700/240, *1.25).. 38.5a is as close as you can get to 40, and 40 is the most common maximum backfeed size on a 200amp service. Any larger requires panel work, or line side tap, which isn't always allowed. So if you have a 200 amp service, they traded some production for upfront cost savings on inverter and further electrical work.

                        Could they have done 10kw, sure. Not sure how much you really miss out on though. From your graph looks like maybe 3kw a day right now? Winter time, probably no clipping at all. 500kwh loss sounds reasonable.

                        Maybe ask what swapping to 10k would cost and do the math on what you're losing?

                        Comment


                        • #13
                          Thanks all for you responses and all the knowledge you have provided. I was concerned that I had some hardware defect in my system given my odd outputs and installers vague responses to my questions. I guess he did not want to talk about the system was being limited by the inverter. I did expect clipping from my system, but I was expecting the panels to decrease output uniformaly.

                          In my installers defense, I was originally suppose to be getting much less kw in panels, but given the non-ideal orientation of my system, I asked him to increase the panels numbers even though there would be clipping. He was very vague about why he did not want to increase inverter size to the 10kw/hr max, but now I see the real reason was likely the length of time it would tie up his crew. I was lucky to have someone who would guarantee me making the SREC 2 deadline and appreciate that his crew was already stretched razor thin. Maybe in the future I could upgrade to a larger inverter, but I don't know if this result in me losing out on SCREC 2.

                          Its also good to know that my output will likely be a little better than I thought now knowing that I'm pretty much at true west.

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                          • #14
                            The inverter is probably fine...Why size the inverter larger if the peak power will never exceed 10kw...I mean there is no way you will see a 7.7kw peak on that array.

                            The dirty truth of solar is that clouds exist and light only reflects so much...So don't feel bad or bummed.

                            I highly doubt you will be clipping much at all...Honestly why all this baloney about clipping? Mother nature has clouds, it's not cost effective to size a system based on potential clipping because if it happens, it happens rarely.

                            You are fine, relax, have a beer. It's all good.

                            Comment


                            • #15
                              Originally posted by Six4KilowWatt View Post
                              The inverter is probably fine...Why size the inverter larger if the peak power will never exceed 10kw...I mean there is no way you will see a 7.7kw peak on that array.

                              The dirty truth of solar is that clouds exist and light only reflects so much...So don't feel bad or bummed.

                              I highly doubt you will be clipping much at all...Honestly why all this baloney about clipping? Mother nature has clouds, it's not cost effective to size a system based on potential clipping because if it happens, it happens rarely.
                              It is a 7.6kw inverter and is clearly clipping ove 500kwh/y. And is peaked at 7.6kw in the graph provided above for hours, and will happen almost daily
                              OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

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