PV Gap

Edith Said:

how to measure the power output from a solar cell over a 24 hour period??

We Answered:

Although, I did this quite differently in college:

I would build a circuit that switches a capacitor from the solar cell to a resistor. So that when you set your solar cell, you couple the capacitor to the solar cell and allow the cell to charge the capacitor for one hour. When you come back, set two probes to trigger and capture the voltage and current waveform across the resistor on an oscilloscope. Then flip the switch to couple the resistor the cap. Once the capacitor dissipates its charge, make sure to reset the switch and face the panel spatially perpendicular to the sun.

I cannot tell you the capacitor or resistor values, as I haven't tried this method, but I know that with the waveforms, you can calculate the energy accumulated every hour in the capacitor by the solar cell. From that you can calculate power. It should be fun to design the values though!

Good Luck!
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In college, basically, I did it the way they described below. The problem was that the solar cell acted differently when I connected a resistive load across it and my professors told me that the readings I got in the lab were not correct. I think the quick explanation is that you would be reading an instantaneous reading of the voltage; the solar cell acts more of a current source rather than a voltage source, so reading the voltage across the resistor instantaneously would not give a correct estimate of what the current is really doing.

If you want to attempt it that way, you should switch a load resistor directly rather than a cap-resistor circuit. Take down the waveform across the load instead of just putting a resistor in series.
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I am curious if a full moon would give any readings in this experiment.

Floyd Said:

Does the angle at which the sun's rays fall on a solar cell affect the power thats produced?

We Answered:

Yes, photovoltaic cells produce in direct relation to the intensity of the input. If the cell is not at an Optimum Angle the output rate is affected. The Solar Collector does not have to be +-24d in alignment, but every little bit helps.