Announcement

Collapse
No announcement yet.

Module Shading What's acceptable?

Collapse
X
  • Filter
  • Time
  • Show
Clear All
new posts

  • Module Shading What's acceptable?

    Hello everyone,

    Is there a standard/recommendation regarding the acceptable degree of shading of a solar panel?

    I am using PVSol to simulate shading from surrounding structures. The results of ‘Shade Frequency Distribution’, expressed in % for each module, is the annual average of irradiation reduction. This number goes from 0% (absolutely no shade) to100% fully shaded. I think I have read that this number should be less than 1%, but I can’t seem to remember the source of this info. Is it true? How much shading is acceptable, in %?

    Thanks

  • #2
    That is a good question. Generally it depends on the goal of offset. The right answer is to balance the production, and costs for the individual site.
    In some areas where utility costs are low, very little shade will make ROI difficult, in other areas where utility costs are high, you can get considerable shade and still have good ROI. Incentives also fall into this. Some incentives are structured such that there is a minimum shade per module or array that needs to be maintained. I haven't seen any that require less than 1% though.
    OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

    Comment


    • #3
      1% would be nice, but 10% or more may be acceptable. As Bruce notes, it depends, to a great degree, on how the shading affects cost effectiveness. There is no firm, simple answer.

      Comment


      • #4
        Originally posted by Esi View Post
        Hello everyone,

        Is there a standard/recommendation regarding the acceptable degree of shading of a solar panel?

        I am using PVSol to simulate shading from surrounding structures. The results of ‘Shade Frequency Distribution’, expressed in % for each module, is the annual average of irradiation reduction. This number goes from 0% (absolutely no shade) to100% fully shaded. I think I have read that this number should be less than 1%, but I can’t seem to remember the source of this info. Is it true? How much shading is acceptable, in %? Thanks
        Keep in mind that shading is only as simple as a panel by panel basis when micro inverters keep all the panels independent. When used
        in strings, one shaded panel can affect many others to a varying degree. A shadow covering only a part of a panel can degrade output
        of all the cells in the panel. Shadows are most important, but usually least present, when the sun peaks for the day.

        Here clouds are much more of an issue (but less predictable) than shadows. Bruce Roe

        Comment


        • #5
          Originally posted by bcroe View Post
          Keep in mind that shading is only as simple as a panel by panel basis when micro inverters keep all the panels independent.
          Micros Or optimized systems...
          OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

          Comment


          • #6
            Thanks everyone.

            I agree with all the above, though I was hoping for a quantitative answer
            I finally tracked down the source of that 1% , but it refers to inter-modular shading.
            "In general, if there is less than a 1 percent annual loss due to shading, then the row spacing may be deemed acceptable." (Utility-Scale Solar Photovoltaic Power Plants, IFC, pg 69)

            PS. I thought micro inverters had become redundant?

            Comment


            • #7
              Originally posted by Esi View Post
              Thanks everyone.

              I agree with all the above, though I was hoping for a quantitative answer
              I finally tracked down the source of that 1% , but it refers to inter-modular shading.
              "In general, if there is less than a 1 percent annual loss due to shading, then the row spacing may be deemed acceptable." (Utility-Scale Solar Photovoltaic Power Plants, IFC, pg 69)
              This is not talking about 1% shading it is talking about 1% production lose due to inter row shading on a tilted system. This is not typical of residential rooftop.

              Originally posted by Esi View Post
              PS. I thought micro inverters had become redundant?
              redundant for what?
              OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

              Comment


              • Esi
                Esi commented
                Editing a comment
                Ok, agreed. These percentages do not quantify the same phenomenon.
                However, they are proportional; Aren't the (system) losses caused by shading, proportional to the 'amount' of shade the module receives?
                So, the reverse should be true: 1% of system loses (due to shaing), should be caused by the module being 1% less exposed to the sun? No? This got too confusing now...lol

              • Esi
                Esi commented
                Editing a comment
                No. I didnt confuse optimizers with inverters. I know about solarEdge technology. But anyways...that's a whole other topic

              • ButchDeal
                ButchDeal commented
                Editing a comment
                no they don't. In a commercial tilted system. the installer puts the modules in place and creates the shadows during winter solstice.
                Other shadowing is at different times of year, day, etc. So 1% shadow does NOT equate to 1% production drop.

                For example a 10% shadow in the evening on an east facing array is going to have very little if any effect on production.

                I would question EVERYTHING that you have been told as the micro thing and this 1% thing are just wrong.

            • #8
              Originally posted by Esi View Post
              Thanks everyone.

              I agree with all the above, though I was hoping for a quantitative answer
              I finally tracked down the source of that 1% , but it refers to inter-modular shading.
              "In general, if there is less than a 1 percent annual loss due to shading, then the row spacing may be deemed acceptable." (Utility-Scale Solar Photovoltaic Power Plants, IFC, pg 69)

              PS. I thought micro inverters had become redundant?
              The quantitative part varied with location, application and time of day/yr. and application. There is no one, hard answer.

              Comment


              • #9
                Following link maybe useful for this topic:
                "Shade and solar arrays: How 10% shade tolerance is re-shaping project design"
                https://www.solarpowerworldonline.co...roject-design/

                Comment


                • #10
                  Originally posted by sajad View Post
                  Following link maybe useful for this topic: "Shade and solar arrays: How
                  10% shade tolerance is re-shaping project design" the amount of time of com
                  A problem is that the term SHADE TOLERANCE is incomplete. Here it refers to the percentage
                  of time for complete loss of module production from time of day/year hard shadows. But it could
                  refer to operation of bypass circuits in strings or reduction of intensity by dirt/clouding.

                  My own feeling is that if weather of the area has much impact, solar calculations to the second
                  decimal place are marginal at best. Bruce Roe

                  Comment


                  • #11
                    Purchase and install an expensive picture window.
                    Cover an acceptable portion of it with duct tape, knowing that the tape will fuse and stick to the glass, possibly being unable to ever be cleaned.

                    That's my view of shade. Shade stresses the panel by reducing electron pathways, bypass diodes are often factory embedded to prevent too much damage or power loss, but those diodes often fail themselves.
                    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 ||
                    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
                    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

                    solar: http://tinyurl.com/LMR-Solar
                    gen: http://tinyurl.com/LMR-Lister

                    Comment

                    Working...
                    X