Plexiglass UV resistance

[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.

[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

[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]

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

[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.

[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

[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.

[lanada]

Plastic spray

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

[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

[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]

Thanks for the nifty update. Got any pics of the assembley ?

[mrfrisky]

Here is a pic. White splotches are cloud reflections.

[dogsbody]

Did similar on solar hot water panels in 1970's. Many still working but slight crazing of the surface, which does not apparently affect the solar gain

[woodypynes]

(Finally) Getting my feet wet with solar panels

Tomorrow, I am about to install my first solar panels. I have the accessories (battery, charge regulator, inverter, etc)...but I am curious about something. Will it hurt or help if I "protect" them with a piece of plexiglass or tempered glass? I only considered this option b/c of hail and "weathering" in general. They just look SO pristine right now, I'd hate to see them rusted (frames) or cracked (hail). I'll take any suggestions, as this is my first go-around with SP.
Thanks guys!!

[Mike90250]

"Factory Built" commercial panels have tempered glass fronts and are generally resistant to small hail. Adding another sheet of glass or anything, will reduce the light, increase heating, and lower output power.