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Photovoltaic problem

  1. Apr 10, 2009 #1
    Im working on a problem that involves a PV module consisting of 40 cells each at .5 volts. The problem models the module as having all 40 cells in series. The PV module is connected to a 5 ohm load. The problem also says to assume that the same current and voltage flows through the PV module and load. So solve for I, V, and P.

    I just need to find the current, power, and voltage for 3 conditions.

    a) when in full sunlight

    b) when 1 cell is in shade

    c) when 2 cells are in shade.

    my question is:

    I know the voltage to be 20 volts in full sunlight and 19.5 volts when 1 cell is in shade....so when 1 cell is in shade I noticed the book saying that one .5 volt cell will now act as a 5 ohm reisistor.....is this true....and why?

    and if that is the case for 1 cell in the shade would I have a total of 10 ohms resistance to calculate the current flowing?
  2. jcsd
  3. Apr 11, 2009 #2
    any ideas?...I can understand a cell not functioning acting as a resistor....but why 5 ohms?
  4. Apr 12, 2009 #3


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    Gold Member

    I would guess it is because that's what someone measured when they shaded an individual cell. Silicon is a semiconductor, so with no light falling on the cell, it turns into a resistor. That resistance will depend on the physical dimensions of the cell.
  5. Aug 19, 2009 #4
    its true , for this case the PV module must protect it by bypass diode
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