Build a 60 Watt Solar Panel

Step 7 Glue down the solar cells

Gluing the cells in place proved to be a little tricky. I placed a small blob of clear silicone caulk in the center of each cell in a six cell string. Then I flipped the string over and set in place on the pencil line grid I had laid out earlier. I pressed lightly in the center of each cell to get it to stick to the pegboard panel. Flipping the floppy string of cells is tricky. Another set of hands may be useful in during this step.

Don't use too much glue, and don't glue the cells anywhere but at their centers. The cells and the panel they are mounted on will expand, contract, flex and warp with changes in temperature and humidity. If you glue the cells too tightly to the substrate, they will crack in time. gluing them at only one point in the center allows the cells to float freely on top of the substrate. Both can expand and flex more or less independently, and the delicate solar cells won't crack.

Next time I will do it differently. I will solder tabs onto the backs of all the solar cells. Then I will glue all the cells down in their proper places. Then I will solder the tabs together. It seems like the obvious way to go to me now, but I had to do it the hard way once to figure it out.

Here is one half panel, finally finished.

Comments

[Valence_4]

Another important thing to greatly improve the panel's efficiency: Solar cells do provide a 0.45volt FORWARD voltage when lit by sunshine but will act as a REVERSE biased diode if unlit. So if a leaf falls on one cell of your panel, the overall efficiency will be HIGHLY reduced by the unlit cell that will absorb a high reverse voltage. This will not only highly reduce the panel's efficiency but may also damage the unlit cell if the panel is loaded. To prevent this, i strongly suggest you to buy 3 ampere shottky diodes (1N5820 for example), one per cell, and solder them un PARALLEL with each cell. The polarity is important. For that, use one cell, put it under sunlight and using a voltmeter, test which side is positive and which is negative. If i remember well, the top side is negative. Then, solder long bare wire (AWG24 will do the job) to each end of the diode and then, solder the bare wires onto BOTH tabs of the solar cells with the CATHODE (banded) side on the POSITIVE side of the cell and the ANODE (no band) side on the NEGATIVE side of the cell. On normal use, the diodes will be REVERSE biased and will have NO EFFECT on the overall panel's efficiency. But in one or a few cells are shaded either by a leaf, a bird or a tree's shade, thee diodes will start to conduct as the solar cell is reversed biased. This way, the whole panel will continue to generate power and the shaded cell(s) will be protected by the diode that will limit the cell's reverse voltage to less than 1/2 volt. I suggest Shottky diodes rather than ordinary 1N5401because of their lower forward voltage (typ. 475mV) compared to classic PN junction diodes (1 volt Vf).

[Itchyzombie]

Or you can Buy more solar sells to provide power for fans to blow them off BTW he said his place is windy all the time.

[bhouse2]

so basically you're telling me that if a large leaf shades 1 solar cell in a series of 36 the voltage drops to 0 becauce it is essentially breaking the circuit that would be expensive to buy 1 diode per cell how come no one else mentions this

[speedstix]

I highly recommend doing this as well. All those cells in series are all affected if one of them is unlit. The current drops to the one cell that is unlit (0 amps).

[americanguy]

Another word of caution about using silicone is that IT IS CONDUCTIVE. BE VERY CAREFUL not to short solder tabs.

[speedstix]

 I had no idea this was true. Luckily the panel I made worked well. I used silicone in strips. 

[bruces]

another way to attach your cells would be to line them up perfectly on a table upside down,then put a dab of silicone in the centre of each cell ,then place your backing on the cells ,after curing you can turn them over and install them in the cabinet .

[Valence_4]

Another way to glue the solar cells in place is NOT to glue the cells themselves. Instead, start to solder all the cells together as shown in this instructable but with leaving 1/2 inch extra tab length between each cell. Place the solar cells on the pegboard, front side up then, using fine long nose pliers, form, with this extra 1-2 inch tab, two "U" shaped bridges, one on each of the joined cells and the "U"'s being bent on the FRONT side of the solar cells. and then tack the TABS, between the "U" shaped bridges, on the pegboard using silicone putty drops leaving the solar cells themselves free to fully expand/retract. And if ever one solar cell breaks, it will be much easier to replace by simply cutting the "U" shaped bridges and removing the broken cell away.

[fimjox]

Another way to go is to use he double sided tape they use for hanging Masonite. You can get it at any decent hardware store. It is gray and mailable and should work fine

[The Lightning Stalker]

I'm not sure I'd use caulk as a glue. I've seen cheap caulk give out in moist conditions and it takes forever to dry in the absence of good airflow. Flexible epoxy sticks much better and is impervious to moisture. Mixing it is a pain in the butt, but it will cure in the absence of air. At the very least, I'd use RTV silicone.