Plexiglass UV resistance

[mrfrisky]

Plexiglass in the Tropics

Started making panels back in '08 for use in the tropics where it rains a lot. Here is the correct procedure for plexiglass after 3 years of tinkering.

1. We use 1/16" aluminum sheet for the back, framed by 3/4 x 1/4" aluminum bar. We use U/V resistant .093" thick plexiglass. We do not enclose with aluminum channel (c-bar) and will explain why below.
2. After attaching to the panel, you must encapsulate cells with Sylgard, Corning, etc, applying a good layer of liquid encapsulant, using a brush. One batch of encapsulant is good for every two panels that are 36" x 30". (36 3x6 cells)
3. Must glue plastic, transparent "necklace beads" in the middle of panel, in between the strings of cells, so that plexiglass does not touch the cells upon contraction.
4. Everything is held in place with stainless steel screws (#10).
5. When attaching plexiglass to the panel, only apply silicone GE-II to the top. Leave sides and bottom attached only by the screws/nuts/washers. These are the areas that cannot be totally sealed.
6. Channeling will only destroy panel. It is impossible to get a 100% waterproof seal here, so panel needs to "breath". When we used channeling, the panels developed moisture/condensation and when daytime brought the sun at its hottest, water became hot vapor and the plexiglass literally exploded outward, became brittle and did not last weeks.
7. After testing for many weeks and months, panels are now totally moisture free and working at its highest rating. Whenever it rains or condensation forms, it quickly dissipates as soon as the sun starts shining.

[Mike90250]

Can i use plastic spray for mosture problem on the front of the cell ?

You can do anything you please with you cells.

If you already have moisture building in them - they are toast, and will soon fail, regardless what you do

[lanada]

Plastic spray

Can i use plastic spray for mosture problem on the front of the cell ?

[russ]

The type of plastic they use for greenhouses is UV resistant - guaranteed for many years.

Plexiglass or polycarbonate for solar thermal can be a good solution.

[dogsbody]

We built thermal panels in the 1975-6 with glass. Thereon for 12 years we used acrylic ( Plexiglass) and most ofthe panels are still in use today.
The panels were made with a GRP case, and the acrylic fixed to the edges of the GRP case with adhesive mastic strip.. It is absolutely essential that the adhesive mastic is of the right type otherwise, plasticisers can cause stress cracking of the acrylic. This is surface microcracking, which through not fatal does reduce the clarity of the panel.

The reasons we stopped using glass were damage in transit, and installation, and weight.
My panels here were built in 1974 - still producing hot water at about 80 degrees C

[Mike90250]

Do not use Plexi. I used it and encapsulated the cells. Due to the expansion and contraction of plexi if the cells are bonded to the plexi they will crack. If you are not going to encapsultate them then it probably would be ok.

Except that Plexiglas (along with nearly all plastics, paints, epoxies and sealers) leaks water vapor like a sieve. Water vapor in an enclosed space = condensation. Condensation inside your solar panel is just as bad as condensation inside your watch.

[lanada]

Do not use Plexi. I used it and encapsulated the cells. Due to the expansion and contraction of plexi if the cells are bonded to the plexi they will crack. If you are not going to encapsultate them then it probably would be ok.

Thanks a lot for your information

[chp]

Do not use Plexi. I used it and encapsulated the cells. Due to the expansion and contraction of plexi if the cells are bonded to the plexi they will crack. If you are not going to encapsultate them then it probably would be ok.

[lanada]

About plexi glass or glass

Can some one helpme,i need to built a new panel but i have my doubts which i can use plexi glass or glass?

Thanks

[Naptown]

actually they are not cheap low end panels, but if you are biased and never did any further research I can see how one might come to the faulty conclusion.

they have a unique market niche. a powerfull portable panel that weighs half as much as a glass one, etc.

Power to weight Ratio is only important in boats cars etc.
Or if you are going to be carrying these around on one of the above.
For most if not all fixed or even tracking modules weight is the least of the issues.

[russ]

I was wrong - these are expensive cheap panels - their big claim is power to weight ratio - important only in regards to carrying panels around.

A unique market niche? Military maybe but in the civilian world no one will pay the premium.

Their advertising BS gets a bit deep for sure!

[Solar-dude]

nope.

actually they are not cheap low end panels, but if you are biased and never did any further research I can see how one might come to the faulty conclusion.

they have a unique market niche. a powerfull portable panel that weighs half as much as a glass one, etc.

[russ]

"I wonder what the reasoning is behind every commercial panel company in the world using low Iron tempered glass is?"
not true
http://www.sbmsolar.com/ does NOT use glass

You can find an exception to anything - probably cheap low end panels

[Solar-dude]

http://www.sbmsolar.com/

"I wonder what the reasoning is behind every commercial panel company in the world using low Iron tempered glass is?"
not true
http://www.sbmsolar.com/ does NOT use glass

[hoodeeet]

Not worth a damn. There is no problem with yellowing of plexiglass despite what some claim. It will never be out in the sun that long.

The main problem is the first sunny warm day the plexiglass is going to expand and shatter all your solar cells leaving you with a pile of garbage. So tempered glass is much less expensive.

Glass is the way to go. The hard part is to figure out a way to sandwich it all together without having an aluminum "c" border around it. i have used plexiglass before becasue it was easy to drill and screw it together.