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melting snow of PV-modules

Discussion in 'Photovoltaics' started by kriegsman, Oct 19, 2003.

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  1. kriegsman

    kriegsman Guest

    Does anyone know an easy way to get rid off the snow on the PV-modules on a
    roof?
     
  2. Steve Spence

    Steve Spence Guest

    install them at a higher pitch. winter elevation should be 15 degrees plus
    latitude.

    otherwise, a broom works well. don't let the snow build up thick either.
     
  3. kriegsman

    kriegsman Guest

    I mentioned the roof, because this is the only available place I have.

     
  4. kriegsman

    kriegsman Guest

    Building regulations in our country say, that the solar panels should have
    the same pitch as the roof . My roof is at 43°. The altitude where I live is
    about 55°.
     
  5. Steve Spence

    Steve Spence Guest

    at 55 degrees latitude, why don't you mount them vertically on your walls
    ....... Your summer months won't be optimum, but you will get better winter
    performance than you would at 43 degrees, and you won't have to worry about
    snow collection.
     
  6. kriegsman

    kriegsman Guest

    List'n guys,
    I have 124 Kyocera KC125-G2 Modules mounted on my roof.
    Same Angle as the roof. Building codes require this.
    So other slope's or tracking systems are no solution.
    I was thinking of using the modules as heating element for a short period,
    so that the snow will slide off. Anyone has experience with this?

    best Regards,
    Zwerius Kriegsman

     
  7. kriegsman

    kriegsman Guest

    List'n guys,
    I have 124 Kyocera KC125-G2 Modules mounted on my roof.
    Same Angle as the roof. Building codes require this.
    So other slope's or tracking systems are no solution.
    I was thinking of using the modules as heating element for a short period,
    so that the snow will slide off. Anyone has experience with this?

    best Regards,
    Zwerius Kriegsman
     
  8. Nick Pine

    Nick Pine Guest

    Silicone? :)
    "Much heat"? You might do a fine job melting snow at 1X.
    That's a hasty conclusion, according to various experts. This
    is one possible way to lessen snow loading and lighten framing.

    Nick
     
  9. Other postings on this topic have discussed reverse voltage to turn the
    photovoltaic (PV) modules into heaters.

    There are many practical and fundamental problems with this scheme.

    To produce heating in a solar cell the voltage across the cell must be either
    the reverse of normal operation or higher than the open circuit voltage.

    PV modules have a characteristic called hot spot heating that can lead
    to failure of the PV module due to partial shading of an array or module.
    PV modules are series connections of solar cells and these solar cells
    have differing reverse voltage breakdown voltages and voltage drops
    when subjected to voltages above the open circuit voltage.

    The typical problem comes in systems with several modules in series and
    several strings of modules in parallel. If a part of a module is shaded while
    the rest of the array is in sunshine, the higher voltage of the operating
    modules will tend to produce a reverse voltage in the shaded cells.
    Due to differenced in individual solar cell reverse current characteristics,
    most of the the voltage will appear across one solar cell and cause
    local heating called a hot spot (it does not produce even heating).

    Because hot spots can start fires, the PV modules are designed to
    incorporate bypass diodes that limit the voltage across sections of
    the series connections (typically at the 4 or 6 volt sections of a nominal
    12-volt module). Since these bypass diodes can be damaged by
    reverse voltages, the individual series strings of PV modules are
    usually protected by either blocking diodes or fuses. All PV modules
    that meet USA UL standards or international IEC standards have
    provisions for the diodes and instructions for the proper installation
    of the PV module.

    PV modules installed according to recommendations can not be
    used as heaters due to the diodes and fuses. If these are omitted
    and an attempt is made to reverse power the PV modules, the
    most likely result will be hot spots and damage.

    Bill Kaszeta
    Photovoltaic Resources Int'l
    Tempe Arizona USA
     
  10. How about just placing a couple loops of plastic or copper tubing
    under the panel and plumb it to a valve so you can pass some domestic
    hot water through it?

    My neighbor has a bunch of zig-zag rubber tubes that do his hot water
    heating. You might even be able to use thermal solar instead of
    tapping the water heater.

    How about a sheet of metal, painted flat black that is bigger than the
    panel and sits under it with fins sticking out each side? Picks up
    solar heat and carries it under the panel. Of course that could be
    bad in the summer. Maybe hinge it so the wings can be folded or
    removed.
     
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