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Measuring Solar Radiation based on Photovoltaic Cells

Hi all,

Many thanks @uncle_bob for all the information provided!
If I use a voltage+current measurement device with a solar cell, can I just easily find the W/m2 by multiplying the current with the voltage without needing to find Isc?


Thank you and best regards
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Hi,

Welcome to the forum.
Please read the theory behind using a solar cell as a cheap pyranometer. You can't use a solar cell for that purpose unless it is working very near the short circuit zone, thus the need to know the Isc to calculate the Rsh
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(18-08-2019, 21:37)HF_ATL Wrote:  If I use a voltage+current measurement device with a solar cell, can I just easily find the W/m2 by multiplying the current with the voltage without needing to find Isc?

Hi and welcome to the forum.

What type of "voltage+current measurement device" do you plan to use?    A normal "wattmeter" needs to be used in association with a suitable load (resistance) and selecting / controlling that is the "difficult" part of solar panel optimisation and management.

But with a simple multimeter you could measure the "Open Circuit voltage" on its Volts range and the "Short Circuit current" (of a SMALL solar cell) on the Amps range.  Multiply those and you might get "somewhere near to" (but more than) the maximum power the cell / panel might be able to produce.  Then you need to take into account the probable energy conversion efficiency of the cell (typically 10% - 20%) and its active area to estimate the solar watts/m2.

What type of "Solar Cell" do you have in mind?  Both the low cost "Epoxy coated" and the "Amorphous Silicon" types have various (long-term) accuracy issues.

Cheers,  Alan.
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Hello,

Thank you @AllyCat and @Werk_AG for your comments.
I have a 0.5 Watt Round Polycrystalline waterproof Solar Panel (2.5v, 250ma, 11.2cm diameter) which I would like to use to measure W/m2 in my home.
I have already some other sensors in my station (temp, humidity, etc.) and decided to include also the solar radiation measurement.
For voltage and current reading I have the INA219 (current shunt and power monitor with I2C interface), which I thought of using for this measurement but seems that the reading the voltage (with a accurate calc of the Rsh) seems the way to go...
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(18-08-2019, 21:37)HF_ATL Wrote:  Many thanks @uncle_bob for all the information provided!

Thank Werk. I only used google translate on Werk's Portuguese post.
I still don't understand it entirely, but then I'm a bit dense Smile
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Thank you both!  Smile
Indeed I'm also Portuguese so the portuguese post would be even better for me  Tongue
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Hi, I came accross this which is for weather stations and other coding boards that may help get the pyranometer off the ground   https://solardcsolutions.com/
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(07-03-2021, 20:27)SSHEEHY Wrote:  Hi, I came accross this which is for weather stations and other coding boards that may help get the pyranometer off the ground   https://solardcsolutions.com/

 Thank you for your info, maybe - it would be interesting...

   

Best Regards
Zdenek

[Image: banner.php]
My outdoor AQM-I: here
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Smile
Seems I should have to reconsider the ridiculously low price of our Solar Radiation / UV interface Kit

[Image: Solar_Interface_v330_kit01.jpg]

Solar Radiation / UV interface kit - 28.90€
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