20Mar 2012

Indoor solar energy harvesting: 3 months data

3 months after having set the solar platforms in an indoor environment, I'm happy to show you here the extracted data :-)

3 months of logging data

First, a little recap from my last article on this topic.

2 monts ago, we concluded that:
- don't even think about extracting solar energy when your solar panel is attached to a wall in a room where no light from the outside can penetrate
- in december, it is a fair assumption to expect more than 20uW if you place your 55*70mm solar panel less than 2m from a window with the curtains partially shut
- in december, if you know that at some point in the day the sun will directly face your solar panel, then you can be sure you'll have more than 150uW in average

So now let's see what we can find with 3 months logging data:

3 months of logging data
Obviously, we clearly see a progression between the 15th of December and 15th of March.

Why this strange 2nd group of 3 bars? Well, in december there were some days where the sun was directly facing the solar panels :

Comparison between 3 months
But that doesn't explain why we can't find the blue peaks in the picture above in January or February. Well... the guy working in this office closed his blinds!

Anyway, let's go back to the logs for the first group of 3 bars (small progression) :

3 months of logging data
Without any surprises, February is brighter than December. Extracted power in February is twice the one of December.

And let's have a look at the platform facing North, placed closed to the window. In my opinion, this is a relevant case as it will only receive the light bounced off the different walls and objects of the room :

3 months of logging data
In this case, average extracted power went from 24uW to 161uW!

Anyway, what conclusions can we draw from these 3 months logging data :
- in february, you can extract in average at least 60uW regardless where you put your solar panel in a room with a window
- power extracted in february is at least twice the one of december
- this project is getting interesting ;-)

Thanks for the visit guys, and don't forget to check out my indiegogo campaign for the toktoktok project!!
Please also have a look at the new online harvesting data repository made by the university of southampton, which seems very promising.

And as usual, here is the excel file!

one comment

1. On Wednesday, October 9 2013, 16:21 by Juno

Thank you for publishing the schematic & following up on the logging. I just found the BQ25504 and now I know it's exactly what I was looking for.

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