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  • #46
    Originally posted by AzRoute66 View Post

    Yes, I presented that chart into post #38 but felt it was Sdss + Srss + [Whatever]. The Whatever is what I thought I might find in the 'DC Module modeled loss' parameter.

    Any insight into the "Shading Mode input = Self Shading" TRM reference given? (I mentioned above but didn't explicitly ask) I don't see anything like that on my SAM Shading page. Don't put any additional time into it, I think I'm losing interest. It only caught my eye as half of the flat roofs in this area have snow white cool-coat and the other half have gravel or asphalt - got to be a difference between those two when you start splitting hairs to the extent SAM models do.
    I think the manual is referring to the "Shading and Snow" entry screen. To engage the self-shading model (for conventional panels), the entry needs to be changed from "none" to "Standard (non-linear)".

    Now is probably a good time to mention that your goat seems to have eaten whatever image you had put into post 38. For what its worth, when I post images, I usually use the windows snipping tool to take a screenshot and upload the file it creates.

    For different roof surfaces, you can manipulate the albedo setting. The model will give a difference between those surfaces if it is set up to show it.
    CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

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    • #47
      Originally posted by J.P.M. View Post
      A fourth point I was trying to make, or a comment, was that perhaps all the discussion about the relatively small difference (if any) of the merits of a 13 vs. 23 deg. tilt may have on lower diffuse fraction due to shading was shifting discussion away from what are perhaps more important other design considerations such as possibly tightening up row pitch made possible from a 13 deg. tilt, or the efffects on performance that a lower tilt may have due to greater fouling that often accompanies such lower tilts.
      I'm not really sure what tightening up the pitch would gain for the OP here. If it tightened up enough to add another row, that could be interesting, but it looks like if the OP wanted more production, a 5th panel could be added to one or more of the four northernmost rows. My interpretation is that no increase in rated power is desired, and the challenge at this point is to install the panels in a way that maximizes their output.

      In post 29 I agreed that it is worth thinking about whether tilt might affect fouling. I don't know if the difference between 23 deg and 13 deg will significantly affect the rate of fouling. The 13 deg tilt is modeled here to give 390 kWh more output over the year, about 2.2%, which feels like a bigger number than the fouling difference between those tilts would take back. But, maybe 15 or 18 would be better. If the racking is infinitely adjustable, maybe I'd split the difference and go with 18. If there are discrete choices that the framing support, I'd probably look for whatever was greater than, but closest to, 13.

      As I also said in post 29, there is a point at which the stress of optimization is not worth it. I've gone deeper into it in this thread because it sounds like in post 3 the OP made a point of specifying 23 deg, and I'd like for others reading this who might find themselves in a similar situation to consider that sometimes, the obvious answer isn't necessarily the right one (but the burden of proof for the less obvious answers should be higher).
      Last edited by sensij; 10-15-2017, 10:35 PM.
      CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

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      • #48
        Originally posted by sensij View Post
        I think the manual is referring to the "Shading and Snow" entry screen. To engage the self-shading model (for conventional panels), the entry needs to be changed from "none" to "Standard (non-linear)".
        OK, the manual is just out of date on how it is labeled/activated. Gotcha.

        Now is probably a good time to mention that your goat seems to have eaten whatever image you had put into post 38. For what its worth, when I post images, I usually use the windows snipping tool to take a screenshot and upload the file it creates.
        That (snipping tool) is precisely how I did it and it looks fine to me. (shows run#/tilt and numerical outputs at top, with three bar graphs below, the lowest of the three being the 'POA shading loss %')

        For different roof surfaces, you can manipulate the albedo setting. The model will give a difference between those surfaces if it is set up to show it.
        Found it. Where you set the surface from 0 - 1, default 0.2. Thanks again.

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        • #49
          Originally posted by sensij View Post

          I'm not really sure what tightening up the pitch would gain for the OP here. If it tightened up enough to add another row, that could be interesting, but it looks like if the OP wanted more production, a 5th panel could be added to one or more of the four northernmost rows. My interpretation is that no increase in rated power is desired, and the challenge at this point is to install the panels in a way that maximizes their output.

          In post 29 I agreed that it is worth thinking about whether tilt might affect fouling. I don't know if the difference between 23 deg and 13 deg will significantly affect the rate of fouling. The 13 deg tilt is modeled here to give 390 kWh more output over the year, about 2.2%, which feels like a bigger number than the fouling difference between those tilts would take back. But, maybe 15 or 18 would be better. If the racking is infinitely adjustable, maybe I'd split the difference and go with 18. If there are discrete choices that the framing support, I'd probably look for whatever was greater than, but closest to, 13.

          As I also said in post 29, there is a point at which the stress of optimization is not worth it. I've gone deeper into it in this thread because it sounds like in post 3 the OP made a point of specifying 23 deg, and I'd like for others reading this who might find themselves in a similar situation to consider that sometimes, the obvious answer isn't necessarily the right one (but the burden of proof for the less obvious answers should be higher).
          Understood.

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          • #50
            This became quite complex for the average Joe. From my understanding, 13 degree tilt will, in conclusion result in a higher annual output vs the 23 degree. I appreciate everyones response and thoroughness. This forum is remarkably helpful and I'm always lurking on it passionately. I'm sure this thread will be quite informative for the next person down the road with the same questions. Unfortunately, after talking with the contractors, they won't budge with the 23 degree tilt so I'm afraid that's what I would have to go with, and later consider changing things on my own if needed. Thanks again to all! I'll post some pics when the installation is complete. Recently got the call to set up a site survey for 2 Tesla Powerwall batteries. Exciting times.

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            • #51
              Originally posted by Techm7 View Post
              This became quite complex for the average Joe. From my understanding, 13 degree tilt will, in conclusion result in a higher annual output vs the 23 degree. I appreciate everyones response and thoroughness. This forum is remarkably helpful and I'm always lurking on it passionately. I'm sure this thread will be quite informative for the next person down the road with the same questions. Unfortunately, after talking with the contractors, they won't budge with the 23 degree tilt so I'm afraid that's what I would have to go with, and later consider changing things on my own if needed. Thanks again to all! I'll post some pics when the installation is complete. Recently got the call to set up a site survey for 2 Tesla Powerwall batteries. Exciting times.
              FWIW, and while I believe 23 deg. is a nominally better choice, I also believe the real world differences in annual output, and cleaning & maint. requirements between the two tilts will be slight, but honest opinions can certainly vary.

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              • #52
                Originally posted by Techm7 View Post
                This became quite complex for the average Joe. From my understanding, 13 degree tilt will, in conclusion result in a higher annual output vs the 23 degree.
                In the world according to the SAM simulation, 13 did produce [slightly] more. The thing about a simulation is that the most interesting question about them is how well they reflect the real world. I wouldn't be especially shocked if it was a bit off-kilter in this case (nor would I be shocked if it was correct).

                [...] after talking with the contractors, they won't budge with the 23 degree tilt so I'm afraid that's what I would have to go with, and later consider changing things on my own if needed.
                Hooray. This is what I proposed in Post #38. In about 1.3 years, when the new car smell is somewhat faded, you will see some sticks that you could install to give you 13 degrees tilt. This exercise will come to mind and you will start designing an experiment. Hopefully, you'll come back and include us either with the result or to help set up a good definitive test.

                Speaking of Post #38, my fantastic Snip-Tool photo with the SAM run graphs is now missing for me as well. (see sensij's comment in Post #46). What do I have to do to get it back in there? - the whole post doesn't make much sense without it. Also, lots of 'Best Of' posts, including some of SunKing's stickies, have references to crucial photos that are no longer are included. Between missing photos and the whole special characters / cut/paste fiasco this board needs a serious tune-up.

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                • #53
                  Originally posted by AzRoute66 View Post

                  Speaking of Post #38, my fantastic Snip-Tool photo with the SAM run graphs is now missing for me as well. (see sensij's comment in Post #46). What do I have to do to get it back in there? - the whole post doesn't make much sense without it. Also, lots of 'Best Of' posts, including some of SunKing's stickies, have references to crucial photos that are no longer are included. Between missing photos and the whole special characters / cut/paste fiasco this board needs a serious tune-up.
                  You might try to edit your post, removing the faulty inline image and attachment and attempt to upload it again.

                  Many of the missing images in Sunking's posts are because he changed the 3rd party service he was using to host his images, and updating all the posted links is tedious. The forum server wasn't always as image friendly as it is now (really, it used to be much worse) so older posts tend to have more linked images than locally hosted images.
                  CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

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                  • #54
                    Originally posted by sensij View Post
                    You might try to edit your post, removing the faulty inline image and attachment and attempt to upload it again. [...]
                    Done. The 'faulty' Snipping-Tool-generated .jpg image is opened and viewed fine by quite a few viewers here, looked great (to me) every time I re-visited the thread until today, and is the same image (renamed) that I originally loaded. It will either persevere, in which case we can wonder how it was originally 'faulty', or it will disappear again, in which case we can wonder how it is 'faulty'.

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                    • #55
                      Originally posted by AzRoute66 View Post
                      Done. The 'faulty' Snipping-Tool-generated .jpg image is opened and viewed fine by quite a few viewers here, looked great (to me) every time I re-visited the thread until today, and is the same image (renamed) that I originally loaded. It will either persevere, in which case we can wonder how it was originally 'faulty', or it will disappear again, in which case we can wonder how it is 'faulty'.
                      Thank you, looks good, and I have no idea what went wrong. It has happened to me before too.
                      CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

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                      • #56
                        To close this topic! Here's the final install !
                        Attached Files

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                        • #57
                          Some things to note:

                          in the end, I went with 15 degree tilt. LG 335's with P370 and SE10000 inverter. No issues with self shading

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                          • #58
                            I'm confused, you're in Miami Florida, right? the SE15k-AUS is a 15kW Commercial Three Phase unit for Australia. There is no 15kW 3-phase for the North America market (at least on the SE website) -- only 10kW and 20kW.

                            Is this residential (split phase 240VAC) or Commercial (three phase 208 or 480 VAC)? If residential (not sure it is). Why not just get the 11.4kW? It's typically priced almost the same as the 10kW. Similarly, when I was getting my system the P400's were actually slightly cheaper (whatever reason) than the P320's.

                            If commercial, then 10kW is your best choice, I believe. From SE specs, you are well within the limits of 13.5kW DC STC for the 10kW AC inverter. Similarly the P320's would be fine for 320W PTC panels. But if you go to any solar wholesaler / retailer and look up the prices. For example www altestore com (fairly expensive as retailers go), you'll see the cost difference between the two residential inverters is (10kW vs. 11.4kW) is only ~$100 or so. (for 3-phase the 10kW is obviously a lot less than 20kW), and the optimizers (P320 vs P400) are the same price @$64 each.

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