Way back in 2010, I bought a pile of 6" square solar cells, with the intention of making a bunch of solar panels. I had no idea that it would take me this long to finish this effort. This was a low-priority project, dependent on acquisition of used shower doors for free. Thanks to craigslist, I was able to find the necessary shower doors, but this took way longer than I anticipated.
Nevertheless, finished it is. By the time I had built 5 panels, the remaining cells I had were not enough to build that sixth panel, due to breakage in transit, breakage due to my clumsiness (these things are *fragile* - in comparison, a potato chip is way robust), and missing collector busses. The seller had included extra cells to cover breakage in transit, but sadly none to cover for my clumsiness. I might be able to resurrect those cells with missing collector busses, but I don't know if that would give me the required 40 cells. So for now, I am finished.
For each panel, no-load output voltage (at zero current) is about 22V, and short circuit current approaches 8 amps, as advertised. But as I have mentioned earlier, you don't get to have short circuit current and no-load circuit voltage at the same time.
Something else I have learned is that the output of solar cells is temperature dependent. The cells produce significantly more power when they are cool than when they are hot. And that dark color means that they will be hot in the sun. The highest output I have seen from my array is on a day that is mostly cloudy (panels are shaded), when the sun breaks thru (panels are in direct sun, but still cool).
So, a realistic assessment of the power output from these panels is about 100 watts each, at our lattitude. This means that I have the capability to produce a little more than 500 watts (including the three little panels that came with Eolian when we got her). That power is directed into a grid-tie inverter... there are no batteries in our system. In essence I am using the power grid as my battery bank. The inverter turns the output of the panels into 110V, 60 Hz and pushes it back into the line, synced with the line power (if the line power disappears, say during a storm, the inverter automatically shuts off to prevent back-feeding the line). If my home is drawing more than 500 watts, part of that draw is supplied by the solar panels. On the other hand, if the house is drawing less than 500 watts, then the solar panel system runs my electric meter backwards. (With a maximum output of 500 watts, I don't think I will ever need to worry about what happens if I end a month with a negative meter reading.)
Sadly, the day that Jane and I got the last panel up onto the roof of my shop was the first day of the fall rainy season. I have yet to see what the finished system can deliver in sunshine. Nevertheless, it feels good to tie the ribbons on another long term project.
(The remaining posts on this project can be found here.)
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