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Best Panel Position for Maximum Snow Shedding (8/12 Standing Seam)

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  • #16
    Mounting panels near vertical will not eliminate snow accumulation entirely. But the amount of
    accumulation is far less on the near vertical than on a a best summer angle, as demonstrated
    by both setups next to each other here. It took some real work to clean inches off the 35 degree
    angle panels, but just a tap on the near vertical panels might cause remaining snow to fall off. In
    some cases so much of the near vertical panels was already clear, that first appearance of good
    sun immediately finished the job. Panels were mounted enough feet above the ground that
    accumulation of snow was no problem.

    The other benefit here was panels gave more output using summer and winter angles, than a
    single fixed setting. Bruce Roe

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    • #17
      My roof is two stories. How I reach the bottom edge of the panels and the strip of roof below them is with standard roof rake with 4 extensions. Definitely not something to do on a windy day as the combination of 4 poles leads to quite a bit of flex but it works. No issues with the strip of roof above the panels. Firemen like the ridge area of the roof clear so they can ventilate the roof if need be. Some areas require it clearance up the sides of the roof

      I have a Iron Ridge mounting system that has top clips that stick up a bit from the seams between the panels. Those little stubs are enough to keep the snow from sliding and make it a PITA to rake the panels. I have even put up an extension ladder off to the side of the array and have raked my panels off from the side in the past.

      Just below my roof array is another smaller wall mount array (my original) that is pivoted at the top and then the bottom is held out from the wall with adjustable brackets. When set at winter angle (30 degrees) the combination of the roof overhang and the velocity of the snow sliding off the roof makes the majority of the snow sliding off the roof miss the lower array.

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      • #18
        My system consists of three rows of panels on a 7:12 pitch roof. Snow will slide off panels with that pitch, I have no doubt it will on yours as well. I am able to reach the first two rows with a squeegee and will pull the snow off if the weather is not forecast to warm up. I attached a picture with some snow on them. A couple of points to consider:

        Make sure that the panels are installed so that they are like shingles, with the bottom edge of the top panel slightly higher than the top edge of the panel below it. Note that mine weren't all installed like that and thus snow will sometimes stick between panels. See picture "snow partial melt". When that picture was taken, my system production was near zero.

        I mounted my panels as close to the bottom edge of the roof as possible. This was so snow would mostly miss the gutters when it slid and not pile up at the bottom. Not necessarily an issue with a metal roof as I assume the snow will just keep on sliding. But I would probably mount near the bottom of the roof.

        An issue with portrait mount is that a small strip of snow across the bottom of a panel is all it takes to eliminate the production from that panel. At least that is the way my Hyundai panels appear to work. They have three bypass diodes so in theory part of the panel can be blocked and you will still get production from portions that are unblocked. I think if my panels were installed "landscape" that the strip of snow along the bottom edge would result in a loss of 1/3 power instead of 100% as it does installed "portrait". Maybe someone who understands how bypass works can chime in and confirm or correct me. I have a string inverter system so this my not apply to you.

        The picture "snow on panels" illustrates another problem you may have. This particular storm came with north wind and I got a big drift on the top of my panels. Had to wait a number of days for warm weather and rain to make that slide.

        And just for fun, here is a video of snow sliding off. https://drive.google.com/open?id=1cP...AthTa-5wWAP8zX
        Attached Files
        Last edited by plannersteve; 04-14-2019, 04:44 PM.
        Sunny Boy 7.7
        30 Hyundai 290RG

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        • #19
          Originally posted by plannersteve
          An issue with portrait mount is that a small strip of snow across the bottom of a panel is all it takes to eliminate the production from that panel. At least that is the way my Hyundai panels appear to work. They have three bypass diodes so in theory part of the panel can be blocked and you will still get production from portions that are unblocked. I think if my panels were installed "landscape" that the strip of snow along the bottom edge would result in a loss of 1/3 power instead of 100% as it does installed "portrait". Maybe someone who understands how bypass works can chime in and confirm or correct me.
          If you look carefully at your panels, you will most likely see the cells are in series columns running
          up and down the long way. With 6 columns, typically 3 bypass diodes each cover 2 adjacent columns.
          With a portrait mount snow across the bottom kills all 6 columns and the 3 bypass sections. If mounted
          landscape, that strip of snow would only cover cells in the bottom bypass section.

          I highly suspect, that very few panels regularly collecting snow, continue to be cleaned
          off for the life of the system. Self cleaning is not very effective here where temps stay
          well below freezing for long times. Bruce Roe
          Last edited by bcroe; 04-14-2019, 04:40 PM.

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          • #20
            Here is a method to estimate loss from chimney. I attached a curve from my system. I've got 8.7 kW of panels oriented at 170 degrees, slightly east of true south. I'm at 48 degrees latitude.

            if you look at the curve I've identified the time of day the chimney would cast a shadow. Then assuming that I'd lose 5 of 30 panels during that time, I'd have a loss of 17% during the morning and afternoon shading time. That comes out to be about 0.68 kWh loss for this day when I generated 61 kWh. You can decide if that is significant. If you moved panels lower on roof, you'd have less shading than this.

            As JPM noted, you'd only have this loss for half the year. My estimate was for a curve from June 24, just about the maximum loss day.

            Bruce Roe, thanks for clearing up how bypass works.
            Attached Files
            Last edited by plannersteve; 04-14-2019, 11:23 PM.
            Sunny Boy 7.7
            30 Hyundai 290RG

            Comment


            • #21
              Originally posted by John_Dumke View Post
              Billroe, I see that you have room for 13 panels in width for portrait mounting. You will be able to save quite a bit in mounting costs if you go with the commercial sized panels. May I susggest a 385 watt panel from Hanwha that I used. 2 rows of 13 panels equals 26 x 385 = 10,010 watts which gets you the system size you are looking for.

              In addition you will save on optimizers or micro inverters if you go that route.
              Those 385 Watt panels likely are 72-cell panels , with a size of around 1x2 metres ,
              instead of the standard 1x 1.65-1.70 metre .


              Both 13 x 60cells and 13 x 72cells would likely not be possible for a common
              string inverter at 600 Volt maximum OpenCircuit at 270+ Watts each panel ,
              especially in cold regions of this globe (≈30V*≈9A) .


              300 Watts divided by 60 cells would be 5 Watts at around 1.5 Volts and 3 Amps .


              The 72cells should have +6V more , than the 60cells ,
              roughly 40 Volts at Umpp and 50 Volts at Uoc .

              600 Volts / 50 Volt-oc ≈ 12 panels in a string .


              Overall , the Tread Starter should consider to leave one
              column out , if portrait , and use that empty space as maintenance walkway .

              From what I have gatered , that portrait installed panels are
              more prone to snow freight damage , than landscape mounted ones ,
              at least in the Alpine region of Allg

              Comment


              • #22
                Originally posted by John_Dumke View Post

                More expensive..... Not Really, because the Renvu price is for a minimum of like 272 or something. The Alt-e price was very competitive. A little expensive for shipping to SoCal, but will be cheaper for you.
                hey john... i was reading about your install and noticed that you had to use solaredge p505 optimizers for your 385w panels. did you figure out why you couldn't use the p400 's? i'm looking at a seraphim 375w panel which isn't in the solaredge designer tool (i had to manually add it) and it only gives me the option of the p505 's.

                i gave solaredge a call and the guy seemed to think that the p400 's would work. then again, he didn't give me confidence that he really knew what he was talking about...

                wrt to alt-e pricing, they seem about 10% higher when i can compare like products (like the solaredge inverters, etc.). they did say they may do price matching but i haven't gone there yet...

                Comment


                • #23
                  Originally posted by billboe View Post

                  hey john... i was reading about your install and noticed that you had to use solaredge p505 optimizers for your 385w panels. did you figure out why you couldn't use the p400 's? i'm looking at a seraphim 375w panel which isn't in the solaredge designer tool (i had to manually add it) and it only gives me the option of the p505 's.

                  i gave solaredge a call and the guy seemed to think that the p400 's would work. then again, he didn't give me confidence that he really knew what he was talking about...

                  wrt to alt-e pricing, they seem about 10% higher when i can compare like products (like the solaredge inverters, etc.). they did say they may do price matching but i haven't gone there yet...
                  RE the p505 - The only tip off was that when using the SolarEdge designer, SE showed the Hanwha 385w panels only being compatible with the P505's. The SE sales rep said that if it is on the website, this is how the SE engineers want it. No real explanation.

                  With regards to having to manually input your panels. Maybe you have made an error and they are listed. Explanation, when I was spec'ing out my system. The Hanwha panels didn't show initially either. I think it was because I had already selected my optimizers. So only panels that were compatible with the p400's showed up. Or maybe I had done something else. Try to go back into the SE designer and select your panels first. Maybe they will show up.

                  Comment


                  • #24
                    Originally posted by John_Dumke View Post

                    RE the p505 - The only tip off was that when using the SolarEdge designer, SE showed the Hanwha 385w panels only being compatible with the P505's. The SE sales rep said that if it is on the website, this is how the SE engineers want it. No real explanation.

                    With regards to having to manually input your panels. Maybe you have made an error and they are listed. Explanation, when I was spec'ing out my system. The Hanwha panels didn't show initially either. I think it was because I had already selected my optimizers. So only panels that were compatible with the p400's showed up. Or maybe I had done something else. Try to go back into the SE designer and select your panels first. Maybe they will show up.
                    FWIW, Good thought. Nice heads' up ball playing there. At least worth a shot.

                    Comment


                    • #25
                      Originally posted by John_Dumke View Post

                      RE the p505 - The only tip off was that when using the SolarEdge designer, SE showed the Hanwha 385w panels only being compatible with the P505's. The SE sales rep said that if it is on the website, this is how the SE engineers want it. No real explanation.

                      With regards to having to manually input your panels. Maybe you have made an error and they are listed. Explanation, when I was spec'ing out my system. The Hanwha panels didn't show initially either. I think it was because I had already selected my optimizers. So only panels that were compatible with the p400's showed up. Or maybe I had done something else. Try to go back into the SE designer and select your panels first. Maybe they will show up.
                      yeah... i did try starting from scratch and selecting the pv panels 1st. still no seraphim 375 panel choice...

                      i also selected a couple of other 375w 72 cell panels from different manufacturers and they too only gave the p505 as an optimizer choice... seems pretty strange because the p400 seems to meet the specs of the 375w panels!?!?

                      thanks!

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