Shade effect on PV Modules

solemiosolemio Registered Users Posts: 16
What is the effect of partial shade on one panel in a string of say eight? Does it diminish the output of the whole string, or just the one panel?


  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Shade effect on PV Modules

    Shade falling across one of a series string of panels affects the whole output - like putting a weak battery in a string of good ones. Sometimes, depending on the size/severity of the shadow, the string will drop to no appreciable charge output.
  • Solar GuppySolar Guppy Solar Expert Posts: 1,973 ✭✭✭
    Re: Shade effect on PV Modules

    The battery analogy is wrong ... solar panels have bypass diodes, so when a panel is partially shaded, the diodes conduct and all that is lost ( using mppt type controllers ) it is that one panels production ( series ). If in parallel, again, only that panels generation is lost
  • mike95490mike95490 Solar Expert Posts: 9,363 ✭✭✭✭✭
    Re: Shade effect on PV Modules

    Do panels ALWAYS have bypass diodes, or only if listed as having them ?
    Powerfab top of pole PV mount | 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

    gen: ,

  • Solar GuppySolar Guppy Solar Expert Posts: 1,973 ✭✭✭
    Re: Shade effect on PV Modules

    I have never seen one or read a data sheet of brand that doesn't have bypass diodes. Its there for the protection of the panel itself, otherwise, all the energy of the string gets dumped into the shaded silicon ( heat ) and burns up the cell
  • peakbaggerpeakbagger Solar Expert Posts: 341 ✭✭✭
    Re: Shade effect on PV Modules

    Home Power had an article awhile back where they tested panel for shading by covering up various combinations of cells. THe short answer was a horizontal stripe of shading across the width of the panel was real bad for production while vertical stripes had less (but still significant impact as the diodes did their thing.
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