I call GE Silicone II "poor mans RTV". It works great. I had problems with a tube of "Brand..X" Silicone which must have had some kind of acid in it. After a few months it rotted the copper wires I had potted. I like your idea of thinning it with mineral spirits, I will try that. I know all the products that are marked "latex" or "clean up with water" are useless.

The other thing that comes to mind with two sheets of glass is the side facing the sun would expand a lot more than the back side. Would it be possible to bond to front sheet of glass and maybe use a very thin Mylar sheet behind the cells?? I know the double glazed windows have to be "spaced" to accommodate this in their frames.

My final note, I have recently noticed some imported panels that have a "folded" interconnect in the long dimension of the panel. Only seen a couple like this from "offshore" I figured they did that to help eliminate the expansion problem as well.

Silicone is thinned by acetic acid - essentially very strong vinegar.  This is corrosive due to both the acidity and conductivity, especially when it is bathing electrodes with a voltage between them and encouraging electroplating / galvanic corrosion.  Not what you want to soak your cells in.

I built six (72) cell panels from Evergreen surplus cells and wired them for 12/24V. I did like you first mentioned and glued the cells to one pane of glass, then sealed them up like a double pane window. I used heated butyl to seal, and primerless auto glass adhesive to mount, not silicone though.

Anyway, 4 of them survived my rough handling with no glass breakage.  They have been mounted and making power for three years now. I have seen moisture in a panel or two after almost every heavy storm we have had here. I have seen no deterioration in any of the connections between cells. My panels are more-or-less vented to the atmosphere, through small holes, and I live in a very dry climate, away from the ocean, with 300+ sunny days/year.

Because I used chipped/broken cells, I get about 10a@24 volts out of my array at noon. I am grateful for all those watts, but I am one of the people that say they would have been watts ahead buying commercial panels. For one thing, I have 2 panels sitting in the garage that need new front glass, because I shattered it, Then there's the experimental 12V 50W panel I made that I cannot implement into my system, because it is 12V.

Don't get me wrong, I really enjoyed soldering over 2400 cell connections  by hand, it was like a meditation. I can point to the panels when people visit and say.. I did that myself! and feel satisfaction in their open jaw reaction... But honestly, dollars to watts, I might have done better buying panels.

Here's my story when I first mounted these panels.
http://www.fieldlines.com/story/2006/9/16/05931/0581

I say, mount the things in silicone. It's better to be an innovator or a failure than a copycat ;-)

Volvo Farmer

I've tried to pluck out the glass pieces out from the silicone, without success...

As the panel is now, it produces around 15W, because of the shattered glass...

Something to have in mind if one are going to bath the cells in silicone. :)

Here are some pictures of the solar sandwich.  This is the cells on the glass waiting for the silicone.

Here are the materials I used.

Mineral Spirits, GE Silicone II, Glycerine, eyedropper, strong mixing stick, and empty 2 liter bottle.  I ended up using 8 tubes of 10 oz silicone.  To 1 tube of silicone I added 8 oz of Mineral Spirits and 80 drops Glycerine.  Next time I will probably add 10 oz of Mineral Spirits to make the mix a little thinner.  I left it thick so the mix did not get under the cells (I hope).  Also had gloves on as it's messy.  Working time with the mix was acceptable although next time I will use a bigger container and mix it all at once.

Here is a finished picture of the sandwich assembly.

I placed wooden strips on the glass over the tile spacers and applied slight pressure a little at a time with the clamps.  I stopped when I saw no more silicone coming out along the edges.

http://www.sungroper.asn.au/project/solar-panel.html

They built their own for a solar car because commercial panels had too much weight.

Today I picked up some 1/2" aluminum U channel and attached it to the edges with Silicone II.  It's just the right size.  This is a rear view.

So another day or two of drying and I will take it outside.

One other note.  The unit seems very solid.  There is basically two sheets of glass with a solid core of silicone between them and I wonder if tempered glass is really required?????

With the u channel frame it feels even more solid.  Next step is get it mounted and see how it handles the elements.  The days are getting shorter here (North of Chicago) and winter is on the way, so it will not see much heat for a while.

I feel confident it will hold up, we shall see.  I think I am going to build another one.

Will update how it works as time goes by.

Cells   75.00
Glass   50.00
SiliconeII  and Such  45.00
Aluminum Channel 15.00

Total  185.00

http://www.acc-silicones.com/products/encapsulants/opticallyclearsiliconeencapsulants.ashx