How do I measure the irradiance of a particular wavelength?

In summary, Dilan is a high school student planning to conduct an experiment on a solar panel. They want to filter out red light and focus it onto the panel to measure intensities and their relation to power output. They are unsure of how to measure irradiance and are seeking resources to learn more about the field. Suggestions include measuring the transmission spectrum of filters, using different color LEDs instead of filters, and taking apart a single solar cell from a large panel for testing purposes. It is recommended to use precise power measurements and to check LED power requirements from data sheets.
  • #1
dilan
72
0
I am still a high school student and I want to do an experiment on a solar panel. I want filter out red light and then focus is it onto a solar panel and measure various intensities and how it relates to the variation of power output from the solar panel.
For this I suppose I should measure the irradiance. But I am not exactly sure on how to do this. Because I am measuring the Irradiance of a particular wavelength does the unit W·m−2 change?
I actually haven't got a good knowledge in this field, but if anyone is kind enough to provide me a link to learn more about this field, I would be really thankful.

Thanks alot.
Dilan
 
Physics news on Phys.org
  • #2
dilan said:
I am still a high school student and I want to do an experiment on a solar panel. I want filter out red light and then focus is it onto a solar panel and measure various intensities and how it relates to the variation of power output from the solar panel.
For this I suppose I should measure the irradiance. But I am not exactly sure on how to do this. Because I am measuring the Irradiance of a particular wavelength does the unit W·m−2 change?
I actually haven't got a good knowledge in this field, but if anyone is kind enough to provide me a link to learn more about this field, I would be really thankful.

Thanks alot.
Dilan

Cool project.
For irradiance, check out:
http://rredc.nrel.gov/solar/spectra/am1.5/ASTMG173/ASTMG173.html

Here are a few books:
1) Jenny Nelson. (2003). The Physics of Solar Cells. Imperial College Press, Covent Garden, London.
2) Harold J. Hovel. (1975). Semiconductors and Semimetals. Academic Press, New York, New York.
3) Antonio Luque, Steven Hegedus. (2003). Handbook of Photovoltaic Science and Engineering. John Wiley & Sons, Hoboken, NJ.

I highly recommend using (3). If you have access to a university library, you can check out an eBook copy.

(1) is a very difficult read - it's grad level.
(2) FANTASTIC book. I would also get this.

I don't know how long this link will be up:
http://www.eas.asu.edu/~roedel/eee498s07/index.html

but take a look at "Analytical Paper - Solar Cell Operation"
 
Last edited by a moderator:
  • #3
Sounds like an interesting project, here are a couple of suggestions.

Depending on what you are using to filter the incoming light, you may want to consider measuring the transmission spectrum of your filters. Good quality commercial filters will have the transmission spectrum supplied to you, in which case this won't be necessary, but if you are using something crude like cellophane, a direct measurement would be very useful.

Typically to measure irradiance you simply take a power measurement and divide it by the area of your detector. There are a number of different detectors you can use, thermocouples and PIN photodiodes are probably the most common.

The units you should use should be W.m^-2 as per usual. You may come across something called the spectral power or spectral irradiance if you do some reading, which will have gnarly units like W.nm^-1 or W.m^-2.nm^-1 - something like that - this unit is essentially power (or irradiance) as a function of wavelength, with the integral of the curve being the total power (or irradiance) across all wavelengths. Since you are inevitably integrating over a finite bandwidth, you should continue to use W.m^-2.

Claude.
 
  • #4
If you are trying to measure spectral response of the solar panel. Then different color LEDs could be a possibility instead of filters. You could get a fair idea of the output intensity from the data sheets for the devices.
 
  • #5
That's a good idea, using LEDs, I would say that would be the cheapest way in fact to get a known spectrum going into your solar cell.

Claude.
 
  • #6
thanks

hi,
Thanks a lot guys, really helpful.
Claude, yes as you have mentioned I am going to use cellophane (or glass paper). I've searched for 1 week in my country for colour filters and couldn't find any. Even to find a solar panel it was really difficult, but I managed to get a panel that's of dimentions 46cm *29.5cm. The only solution for this would be LEDs, but I am not sure whether the power of LEDs will be enough for a fairly large solar panel. Using LEDs will give me precision, but I was wondering whether the power given of by a lot of LEDs will be enough for me to collect sufficient data. :frown:
 
  • #7
Large panels like the one you have, are a collection of single solar cells. For purposes of testing it will far easier to illuminate a single cell (a few cm^2) than a panel as the parts of the panel that don't get illuminated will just be resistors and diode drops.
A few LEDs will cover a single cell, but for the panel you have it might be hundreds.

You can work out the LED power requirements from the data sheets.
 
  • #8
NoTime said:
Large panels like the one you have, are a collection of single solar cells. For purposes of testing it will far easier to illuminate a single cell (a few cm^2) than a panel as the parts of the panel that don't get illuminated will just be resistors and diode drops.
A few LEDs will cover a single cell, but for the panel you have it might be hundreds.

You can work out the LED power requirements from the data sheets.

They are designed to withstand the environment. I have heard that they can be quite difficult to take apart, so be careful.
 
  • #9
You can buy a single cell for a couple $ or salvage some from somthing like an old solar calculator
 

1. What is irradiance and why is it important to measure?

Irradiance is the amount of radiant energy per unit area received from a particular source. It is important to measure because it can help determine the intensity of a particular wavelength and its effects on materials or organisms.

2. What tools are needed to measure irradiance of a particular wavelength?

The main tool needed is a spectrophotometer, which measures the amount of light absorbed or transmitted by a substance at a specific wavelength. Other tools may include a light source, a detector, and a computer for data analysis.

3. How do I calibrate the spectrophotometer for accurate irradiance measurements?

To calibrate the spectrophotometer, you will need a blank sample with no light absorption. This could be a sample of pure solvent or a blank cuvette. Once the blank is in place, the spectrophotometer can be set to read 100% transmittance, which allows for accurate measurements of absorbance for other samples.

4. Can I measure irradiance of a particular wavelength with a standard light meter?

No, a standard light meter is not capable of measuring the irradiance of a particular wavelength. It is designed to measure overall light intensity and cannot differentiate between different wavelengths of light.

5. How do I convert irradiance measurements into other units, such as radiant flux or photon flux?

To convert irradiance measurements into other units, you can use conversion factors based on the specific units you are using. For example, to convert irradiance to radiant flux, you would multiply by the surface area over which the light is being measured. To convert to photon flux, you would need to know the energy of each photon at the particular wavelength being measured.

Similar threads

Replies
11
Views
1K
Replies
11
Views
2K
Replies
5
Views
882
  • Other Physics Topics
Replies
8
Views
1K
  • Precalculus Mathematics Homework Help
Replies
9
Views
4K
  • Other Physics Topics
Replies
4
Views
4K
Replies
2
Views
6K
Replies
6
Views
2K
  • Quantum Physics
Replies
1
Views
772
Back
Top