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Which solar panels will work better in shaded area: Panasonic or REC

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  • Which solar panels will work better in shaded area: Panasonic or REC

    I am trying to decide which solar panels to choose. I have two contractors with about the same quotes (less than $1k difference) but one is using 19 x Panasonic HIT+ VBHN340SA17 (with Enphase IQ7X) and the other is 17x REC 370 Alpha Series (with Solaredge and Optimizer).

    I do get some shadings in the afternoon starting at 3pm onwards on two sections of my roof. Based on my research, REC have half cut cells (6 strings in series) so it works better in shaded areas.
    I am not sure about Panasonic though. Is Panasonic better than REC in regards to shading?

    Another option that I consider is to use the small roof section on top of my garage as well. It can fit 4-5 panels on that section. I can cut the tree to remove shading on the right side during early morning. The left side will get some shading as well but not until 6pm (due to my neighbor's house).


    House_shading (2).pngSite Plan_REC (2).png
    Site Plan_Panasonic.png


    Thank you.

  • #2
    The operative question is not which solar panels but the micro inverters versus the optimizers. Not enough information to be able to advise.
    It all depends on how much shading. If every panel is shaded but one the single microinverter will put out power. A string inverter would probably not have have enough voltage to put out any energy. You need someone with a device that can quantify the shade throughout the year. I was lucky to find someone in Norther California that could do that.
    9 kW solar. Driving EVs since 2012

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    • #3
      Your daily power curve will start dropping shortly after 2pm. As panels get small areas shaded, their amp output of shaded cells is reduced, throttling the whole panel , The panels internal bypass diodes will help alleviate the voltage drop, but at the expense of daily heating of the diodes, which are not meant for poor install locations. Then the diodes go bad.
      You might look as panels that have embedded "Active Bypass" devices, which are FET based switches instead of diodes.....
      here's a tech article about that
      https://www.digikey.ca/en/articles/a...nd-performance

      With partially shaded panels, there is not much to regain, but you can cut the losses. And partially shaded panels will always slowly be sustaining damage.
      Powerfab top of pole PV mount (2) | 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 ||
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      • #4
        Originally posted by Ampster View Post
        The operative question is not which solar panels but the micro inverters versus the optimizers. Not enough information to be able to advise.
        It all depends on how much shading. If every panel is shaded but one the single microinverter will put out power. A string inverter would probably not have have enough voltage to put out any energy. You need someone with a device that can quantify the shade throughout the year. I was lucky to find someone in Norther California that could do that.
        One is using Enphase IQ7X (240V) and the other is SolarEdge with Optimizer SE6000H-US (240). Solar system size is about 6.5kW.
        Correct me if I'm wrong, but SolarEdge with optimizer will be able to handle the shading the same as micro inverters (Enphase) do right? If not, then I need to go with micro inverters.

        The shading starts at the lower left, as indicated in the photo, and moves towards upper right. For example, those 4 panels will be shaded starting about 3pm - 5pm.

        House_shading_LI.jpg

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        • #5
          Originally posted by utsug View Post
          .......
          Correct me if I'm wrong, but SolarEdge with optimizer will be able to handle the shading the same as micro inverters (Enphase) do right? If not, then I need to go with micro inverters.
          It all depends on how much shading you have. The only way to quantify that is with a survey. Some installers have the equipment to do that. I paid a guy to give me that analysis. There is also a device you can rent that will give you the same info. I forgot the name but a few well framed queries on the internet may turn up the device or another poster here may remember.

          Generally micros and optimizers should perform the same with moderate shading. Moderate is not a defined term and there are those that say a string inverter can be cost effective compared to both optimizers or micros with moderate shading. My earlier point was about serious shading that would drop the minimum voltage below what a string inverter with or without optimizers would be able to produce. In that situation having a few micros producing might be better that nothing, especially if that was in the afternoon when you might be earning $0.50 per kWhr.
          The bottom line is the answer is a quantitative result that requires quantitative input. There is not enough data for anyone to give you anything more than a coceptual answer.
          9 kW solar. Driving EVs since 2012

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          • #6
            If your shading starts at 3pm, you will still be getting most of the possible
            energy. If bypass diodes do fail, they can be replaced at the panel junction
            box. Another way, wire a couple more diodes in parallel with each of the
            existing diodes, or get some much bigger diodes. The problem would be
            weather proofing them. Bruce Roe

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            • #7
              FWIW, I rarely have seen or heard of diodes being a major issue due to shading. I live in the relatively cold shady northeast so maybe our lack of temperature extremes offsets potential diode failure?. I would be far more worried about company longevity to back up any long term warranty issues. Panasonic was early on in the game and seems to be sticking around. Does the other panel firm have the same potential longevity?. I am not a fan of any rooftop mounted electronics but in this case it looks like you need them so the simpler is better approach leans towards the optimizers but in each case its the individual companies reputation. Sad to say both are moving target on reliability as I have not seen any third party comparisons of MTBF for optimizers and microinverters.

              Enphase sells a truck load of micros to solar firms as they are the ultimate plug and play solution, if there is an open space on the trunk cable they can plug in a panel while optimizers do require some string sizing and possibly multiple inverter models in stock depending on array sizing, this means more inventory on the floor of the installer versus micros. Mounting the inverter also takes a bit more planning and space although my guess is the Enphase gateway probably takes up at least some of that inverter mounting time.

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              • #8
                Depending on what you have on hand but my solution would be to do Time lapse photography on each section of the roof over a 10 hour period from a proper vantage point. If you have a GoPro or some other camera that can do snapshots every minute you will be able to stitch together a very good video of what is happening with the shading. Any installer worth their salt should be able to look at the video and advise you.
                Also its really handy to use one of the Solar sun trackers Apps that have VR or allow you to move through the months to see the sun angle for each month. I am not going to name any of them in case that's not allowed but one of them on the Apple App store has a very good Polar Map function that puts your house using Google Maps in the center and allows you to slide through the months and see the suns angle changes. Couple that with the Time Lapse and you will have a good idea of how the shadows will change through the months.

                If it ends up being really bad then yes micro inverters might be the best way to go. If it's not that bad then let the bypass diodes take care of the shading and go with a string inverter system.

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                • #9
                  Originally posted by utsug View Post
                  Based on my research, REC have half cut cells (6 strings in series) so it works better in shaded areas.
                  An article titled Half Cut Solar Panels: Higher Efficiency & Better Shade Tolerance explains half cut panels.

                  "To make their voltage similar to standard panels the half-cut cells are wired together differently. There are 2 lots of sixty series-connected cells that operate at 30V each. These two 30V halves are then connected in parallel. Voltages in parallel stay the same, so the panel remains at the standard 30V."

                  Panel orientation might make a difference depending how shade progresses across your roof. The article is a good read.

                  Also, I sound like a broken record on this forum, but Tigo optimizers with a String inverter might be an option worth considering.

                  I know you didn't ask about other things, but for me, how installers plan to route wires and roof penetrations are important to me.

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