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i knew shade would perform poorly but 3%?

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  • i knew shade would perform poorly but 3%?

    I have an off solar system with 10 300 watt panels with 5 strings of 2 in series each. they run to an MPPT inverter. When they are all shaded (5pm) the panels only deliver 3% of their rated capacity. There is still sun all around them and shining on the trees. All panels are fairly new. I knew panels perform poorly in shade but 3%? something has to be wrong. Thanks

  • #2
    Bummer, you bought the wrong panels. You need Shade Panels, not Solar Panels.

    Sad but true, if the panels are not in strong sunlight, they are pretty much useless. Even the angle of the sun is strongly related to the amount of power they produce. Most arrays produce best between 10am and 2pm. those 4 hours are better then the other 6 hours of lower light.

    In the rain (shaded by clouds) my array puts out about 1% of it's nameplate power. That's why we off-gridders have generators.
    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

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    • #3
      I expect panels to perform in the 10% to 25% range under moderate clouds. Shade can
      be worse, but you might be able to do something about that. I have a chain saw.
      Bruce Roe

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      • #4
        Your eye is log and panels are linear to intensity. I've seen even a wisp of a cloud drop panel output to a small fraction. I live in shade. If I can get 60W out of 500W of panels I am happy.

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        • #5
          PAR is a way to measure light. The sun is 1000 par and the lights in your house are 15 par....be happy you are getting anything.

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          • #6
            I experiment with a lot of solar circuits and it is helpful to know about what your panels could produce. I have two small pilot panels in parallel on different corners of my array. They go into a 56 ohm resistor and will only produce about 7V, less than half the power point voltage. This insures I'm getting close to the Isc current. Two in parallel give me a good average. A voltage divider adjusts that voltage to 1.00V at noon on my best day. Today it is cloudy with rain and the reading is 0.06V or 6%. Nothing worse than wondering if your panels are producing when your only source of information is those panels. For a couple bucks you can build one with a couple old solar lawn lights.

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            • #7
              5 PM in the evening and the panels are in the shade? The panels aren't going to produce anything meaningful at 5 PM even if they were still in the sun. By 5 PM around here, the solar day is over and what is left of any direct rays of sunlight is shining on the backside of my south facing panels.
              Dave W. Gilbert AZ
              6.63kW grid-tie owner

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              • #8
                Originally posted by diptotto View Post
                I have an off solar system with 10 300 watt panels with 5 strings of 2 in series each. they run to an MPPT inverter. When they are all shaded (5pm) the panels only deliver 3% of their rated capacity. There is still sun all around them and shining on the trees. All panels are fairly new. I knew panels perform poorly in shade but 3%? something has to be wrong. Thanks
                Nothing is wrong. What the others have posted might explain the issue but in true sense you really need to study how a solar pv cell works and why it will not produce if the sunlight is not directly pointed at it.

                Sorry your system is not performing as you expected but at least you are getting some production when the panels are not in the shade.

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                • #9
                  Thanks all. Good to know that this is normal. It's a shame though because when the sun is shining I have to throttle my current to not charge my batteries with too much current. I guess my system is just not working. And winter is coming! I would be curious to know how off-grid people survive winter if their system produces only 3% for a whole, cloudy winter week. And even if I had an annoying generator, I cannot quick charge my batteries without damaging them. Confusing. Thanks

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                  • #10
                    Originally posted by diptotto View Post
                    Thanks all. Good to know that this is normal. It's a shame though because when the sun is shining I have to throttle my current to not charge my batteries with too much current. I guess my system is just not working. And winter is coming! I would be curious to know how off-grid people survive winter if their system produces only 3% for a whole, cloudy winter week. And even if I had an annoying generator, I cannot quick charge my batteries without damaging them. Confusing. Thanks
                    Noon and cloudy can be a lot more power than 5PM and in the shade.
                    Really depends on how much cloud cover.
                    FWIW, my grid tie system I have some panels in the shade at 5PM and some pointing west in the sun. The ones pointing west were doing ~130W (285W panels) at 5pm yesterday. The ones in the shade pointing east were doing 10-15W. At noon they were both doing ~165W (west peaked at ~2:30PM, east peak at ~9:30AM)

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                    • #11
                      Which is more annoying:
                      a) buying new batteries
                      b) obtaining & running a generator to avoid buying new batteries

                      Those are your winter choices. it sucks, but even with my reduced loads in winter, if I don't get 2 hours of good sun (noonish, not 3pm) I have to run generator.
                      here's my past winter reality: ( which is why I went NiFe batteries instead of lead acid, they don't care about SOC )

                      CloudCover_11-2018.gif
                      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


                      • #12
                        There is also a min voltage level that has to be met before the electronics in the inverters will turn on and start using the power from the panels at all. This level is different for almost all inverters and micro inverters.

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                        • #13
                          I am considering panels from REC, that are split. The goal is to harness the most power, when shade starts peeing in your Wheaties: https://www.solar-electric.com/rec-s...ine-panel.html

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                          • #14
                            Originally posted by Buck Rogers 2000 View Post
                            I am considering panels from REC, that are split. The goal is to harness the most power, when shade starts peeing in your Wheaties: https://www.solar-electric.com/rec-s...ine-panel.html
                            It all depends on whether it is partial shade and the nature of of it. One would almost need to see a time lapse video of the location during the seasons to really give you any meaningfull advice. There are camera type devices that can plot how much trees will block the sun.I saw one being used in Mendocino for a barn that had partial shading. Is your location plotted on Google Sunroof? That may give you some crude approximation about your roof.
                            9 kW solar, 42kWh LFP storage. EV owner since 2012

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                            • #15
                              Originally posted by Ampster View Post

                              It all depends on whether it is partial shade and the nature of of it. One would almost need to see a time lapse video of the location during the seasons to really give you any meaningfull advice. There are camera type devices that can plot how much trees will block the sun.I saw one being used in Mendocino for a barn that had partial shading. Is your location plotted on Google Sunroof? That may give you some crude approximation about your roof.
                              I can't speak for the OP but my roof hasn't been built yet. Google Sunroof seems interesting, my area isn't covered by the program.

                              You may have just cost me $1000.00, cause now I have an EXCUSE to by a drone!!! I actually don't think I'll need one. I had my trees pruned WAAYYYY back and my roof will be southern facing.

                              Regardless, the REC 315 panels are the right price and power output I should need. Mounting is another thing I'm trying to figure out. My Tuff Shed garage will have a beefed up roof, for snow and panels. In the summer, I'd love to figure out a way to keep my panels cooler than ambient absorption. I'm considering some sort of radiator system or even just having an adjustable rail. Something that I may lower in the Winter, to transfer heat to the garage and raise in the Summer so it won't. I would hope the added space will allow for heat dissipation. We'll see.

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