0
\$\begingroup\$

I'm wondering what the frequency response of a solar cell is. Does a solar cell behave like a low pass filter e.g if i switch a load at 1 MHz, 10 MHz, 100 MHz ? Does the output power decrease if the frequency is too high ?

I'm asking because there exists a Maximum Power Point Tracking Method which is called "Pertub and Observe" . I'm wondering how fast you can change the load and measure the voltage at the load (e.g with a high speed adc) and still get accurate readings.

Will i have problems regarding the frequency response of a solar cell if I change the load 1 Million Times(e.g with a appropriate Transistor) and read the result with a high speed ADC, let's say with 1 Mega Samples per Second.

\$\endgroup\$
  • 1
    \$\begingroup\$ What would be the point of using such a ridiculous sample rate? Conditions that affect the output of a solar panel simply don't change anywhere near that fast. \$\endgroup\$ – Dave Tweed Oct 3 '17 at 13:01
  • \$\begingroup\$ You say "solar cell" so I think: large cells for converting sunlight into electrical energy. The sun's light intensity changes are quite low in frequency so how would the frequency response matter? Unless you mean photo diode or photo transistor which are light sensitive sensors? \$\endgroup\$ – Bimpelrekkie Oct 3 '17 at 13:11
  • \$\begingroup\$ @Bimpelrekkie I mean solar cell, yes. At both: Yes you are both correct, the environment doesn't change that fast but this is not the reason for my question. The reason for it is, that the solar panel powers a circuit which needs to be disconnected during the mppt measurement . That means in the meantime the circuit needs to be powered by Capacitors. The shorter the measurement time the smaller the capacitors may be. I'm aware that there a alternatives, but i'm currently researching the feasibility about this method hence the question regarding the frequency response. \$\endgroup\$ – KoKlA Oct 3 '17 at 13:28
  • \$\begingroup\$ OK, but then you're not really switching the solar cells themselves then. You're switching the load of the solar cells. \$\endgroup\$ – Bimpelrekkie Oct 3 '17 at 13:34
  • \$\begingroup\$ @Bimpelrekkie yes exactly. I should have worded the question a little bit better. \$\endgroup\$ – KoKlA Oct 3 '17 at 13:49
2
\$\begingroup\$

Solar cells have a capacitance, like all diodes, and the leads have an inductance. That will cause a filtering effect at higher frequencies.

But the transistor also has a soft limit on effective switching

\$\endgroup\$
  • \$\begingroup\$ Thank you for the response and the link to the paper. In the paper there is a clear difference between 1kHz and 2.5 kHz. So using extrapolation I assume it will be really bad at 1MHz. \$\endgroup\$ – KoKlA Oct 3 '17 at 13:08
0
\$\begingroup\$

The solar cell is a forward biased diode junction. At one amp, the slope of the resistance is 0.026 / 1amp = 0.026 ohms. If Cjunction (forward bias) is 1uF, the timeconstant is 26 nanoseconds, or 40/6.28 = 6MHz F3dB.

Now what is the capacitance of a forward-biased solar cell?

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.