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Can solar panels be safely short-circuited?

Discussion in 'Electronic Basics' started by Pimpom, Dec 19, 2012.

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  1. Pimpom

    Pimpom Guest

    Can solar panels be safely short-circuited while they are fully
    illuminated? I've looked at the specs and I understand the
    concept of MPP, conversion efficiency, etc. I have no particular
    design or application in mind where short-circuiting the output
    plays a role - just that it might be useful to know.
     
  2. Pimpom

    Pimpom Guest

    I mean safe for the panel. Please disregard consideration of
    external circuits.
     
  3. Tom Biasi

    Tom Biasi Guest

    Usually not a problem. Most panels run close to their short circuit
    current capability.
     
  4. I use photodiodes 'short circuited' (into a TIA opamp circuit). It
    doesn't seem like short circuiting a solar panel could hurt it. (But
    I've never used one!) It might be useful as the short circuit current
    would be some measure of the total intensity. Are the panels all just
    single 'diode drops' or do they sometimes put a few in series?

    George H.
     
  5. Pimpom

    Pimpom Guest

    Thanks.
     
  6. Pimpom

    Pimpom Guest

    I didn't get that right away but let's see (basic college
    thermodynamics is >40 years in the past). The panel receives
    solar radiation, much (most?) of which is thermal and the black
    panel is efficient at absorbing it. So the panel gets heated up
    quite a bit. But some of the radiant energy is converted to an
    electrical potential. If that electrical potential is
    short-circuited, there's no change in the power expended in the
    cells, and therefore no additional heat produced. Is that the
    logic?

    But then not all the radiation is thermal and the non-thermal
    part is also converted to electricity. Wouldn't that produce
    additional heat if it's short-circuited?
     
  7. Pimpom

    Pimpom Guest

    I have one panel as a sample and it has 39 cells in series.
    Judging from the size, I'd guess the power rating as somewhere
    around 50W. Its open circuit voltage in bright sunlight is about
    23V. I haven't tested it yet to plot its characteristics under
    different levels of load and sunlight. No datasheet, and the
    company has only a rudimentary website.

    Someone gave me the sample to play with and see if I could turn
    it into something useful. It seems they have truckloads of the
    things but they don't know what to do with them. I didn't bother
    asking why they bought them in the first place. Probably with
    some vague idea of using them as backup power.
     
  8. Jasen Betts

    Jasen Betts Guest

    If you short circuit them they will heat up, there will be the
    same amount of heating as if you leave them open circuit and
    unloaded, just via a slightly different mechanism.
     
  9. That seems right. The energy has to go somewhere.
    But when the cell is open circuited there's no energy 'lost' from the
    cell either. The photo-generated e-h pairs recombind in the silicon.
    So the cell runs at it's coolist when you are pulling just the right
    amount of energy out of it.

    George H.

    - Hide quoted text -
     
  10. Right!... sorry I should have read to the end of the thread before
    posting.

    (Can you see the temperature rise 'in practice', as opposed to 'in
    theory'?)

    George H.
     
  11. Jasen Betts

    Jasen Betts Guest

    It was an issue for the builders of the sunshark
    http://en.wikipedia.org/wiki/Sunshark_Solar_Car_Team
    I had a chat with them around 1991 some time.

    In their design the silicon wafers are beneith a layer
    of fibreglass abd the overheating was causing delamination.
     
  12. Bret Cahill

    Bret Cahill Guest

    Can solar panels be safely short-circuited while they are fully
    Not as much hotter as they would get cooler in the shade w/o a short.


    Bret Cahill
     
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