1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Irradiance and Isc and Voc of a solar cell

  1. May 17, 2016 #1
    When irradiance increases what happens to open circuit voltage and short circuit current of a solar cell? Do they both increase linearly? Because temperature affects open circuit voltage, so I'd assume open circuit voltage doesn't increase linearly then...
     
  2. jcsd
  3. May 18, 2016 #2

    Baluncore

    User Avatar
    Science Advisor

    Voltage does not increase linearly with radiance. Current does increase with radiance.
    But you want power so you must find the point where the product of voltage and current is close to the maximum.
    That cannot be with short circuit current because then there is no voltage.
    That cannot be with an open circuit voltage because then there is no current.
    https://en.wikipedia.org/wiki/Maximum_power_point_tracking#I-V_curve
    Voltage drop across the resistance of the cell increases with temperature and dominates voltage reduction due to rising temperature.
    PN junction voltage falls slightly with temperature increase.
     
  4. May 19, 2016 #3
    Ok, so open circuit voltage doesn't increase with irradiance, so then it must decrease due to temperature effects.

    I was confused between light intensity and irradiance. As light intensity increases open circuit voltage and short circuit current increase, but light intensity and irradiance are two different things.
     
  5. May 19, 2016 #4

    Baluncore

    User Avatar
    Science Advisor

    Correct. All other things being equal, the open circuit voltage will have the negative temperature coefficient of the cell material, probably silicon.
    Avoid the confusion by referring to incident power. Only photons with wavelength, energy sufficient to overcome the semiconductor band gap are being considered.
    Twice the power, is twice the photons, is twice the electrons, is twice the current.
     
  6. May 22, 2016 #5
    As irradiance increases, we can assume temperature will increase (more irradiance=later in the day=temperature increasing), this means that Voc decreases due to temperature effects, and short circuit current increases due to more irradiance.
     
  7. May 22, 2016 #6

    Baluncore

    User Avatar
    Science Advisor

    A cell is never operated at open-circuit voltage or short-circuit current. It is operated close to the MPP.
    As output current increases the voltage falls since the cell internal resistance drops more voltage.
    There is also the smaller drop due to the temperature of PN junction.

    The rising panel temperature is is due to heat from;
    1. Internal I2R resistive losses.
    2. Incident long wavelength radiation with insufficient energy to overcome the bandgap.
    3. Thermal environment later in the day as angle to Sun changes and as air warms.
     
  8. May 23, 2016 #7
    "
    A cell is never operated at open-circuit voltage or short-circuit current.
    Solar cell is operated close to the MPP.
    That cannot be with short circuit current because then there is no voltage.
    That cannot be with an open circuit voltage because then there is no current."

    thank yall for this simple summary
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Irradiance and Isc and Voc of a solar cell
  1. Better Solar Cells (Replies: 29)

  2. Solar cell information (Replies: 2)

  3. Solar cells project (Replies: 6)

Loading...