Science Buddies: "Ask an Expert"

How do we detect the energy levels of blue, red and green through a solar panel? More specifically, what is the most affordable way to detect energy from a solar panel? I have a multi meter but it doesn't have watts. Any ideas on how I can compare the energy levels? I read blue would have the most energy but I need to prove it or see it for my project. Thank you so much.

Annelurch - It seems to me that you will have several variables to contend with in this experiment. It sounds like you are trying to measure and quantify the spectral response of the solar panel responding to various wavelengths of light. In this kind of measurement the calibration of your light source will also be a problem. Are you using some form of colored transmission filters to create broad categories of red, green and blue light? You will not know how much energy is absorbed by/passed through the filters assuming you are using a white light source? The white light source is also suspect in that it probably has a varying energy output that varies with wavelength.

With regards measuring power, you can connect the solar panel to a resistive load and measure the voltage across the load to calculate power output using the equation I(current in amps) = V(voltage across load)/R(value of resistor). Using the derived current value (I), multiply it times the voltage to get power dissipated in the load in Watts. Alternatively you can use the multimeter to measure the current directly and calculate the power in Watts using the equation I^2 (current squared) times R. This may not be optimized to the characteristics of the solar panel, but at least is a relative measurement you can use in the experiment.

Perhaps some other experts are more familiar with this experiment and can offer some different approaches.

Rick Marz

Thank you for answering. I am 12 and I think your answer is above my understanding. Can you simplify your answer for me please?

I was planning on having 1 shoe box with a solar panel in it. 3 lids with each lid having its owN colored filter. I want to show when using a blue filter the numbers in the multimeter would be higher than a red filter. Is this possible to show? How can I prove that blue is stronger than red using the light from the classroom going through the filters. Will my multimeter work?

Thank you again.

Annelurch - Sorry about the too technical response. One of the goals of a science experiment is to show, through the scientific method, that your hypothesis is supported by measured results. Your hypothesis seems to be that the blue filtered light is transmitting more energy as converted by the solar cell than red or green filtered light. Why do you believe this to be true? How did you come to this hypothesis? My first response was to suggest that there are too many uncontrolled variables in your presumed setup. What is the 'light' in your classroom made up of? More red or more blue energy? Sunlight? What is the conversion capability of your solar cell to blue or red light. If the lighting in your classroom comes from incandescent light bulbs, it may be producing more energy in the red spectrum, while if the lighting is from a fluorescent, or mercury vapor bulb, it may in fact be more blue in spectral content.

For additional reading, look at this Science Buddies experiment that deals with measuring the input energy and solar cell output as its experiment. Under 'Variations' at the end it touches on the matter of different colors or wavelengths and their effect, but it seems to be a more advanced procedure. It does require an understanding of the nature of your light source as I mentioned. In any case, your multimeter can be used to measure voltage across, or current through the load on the solar cell. Those values can be converted into power comparisons as I mentioned before. Hope this helps.

https://www.sciencebuddies.org/science- ... p014.shtml

Rick Marz

Thank you so much!! This is very helpful.