Solar Panel Building

[wayne]

Hi

I have some cells coming soon and been reading alot on building. One thing that bugs me is some prefer for Ventilation and the other side is Seal it all up!

My plan was to mount the cells on 3/16" Plexiglas back plate and for front too. Seal with 3/4" plex strips. No holes on edge and use L bracket for top/ bottom to hold panel. So all sealed between Plex. Might use thin aluminum U around edge and silicon this on for looks.  Has anyone done this and would the plex bend and warp over time. Using Temp glass seems to much for a few pieces. Or some I have seen just a wood back, open vent it and cover it.

Thanks

Wayne

[disaray1]

Hi Wayne. This is kind of a catch 22. If you seal it up, any air inside will contain some moisture, and will condense on the inside of your plexi. If you leave it ventilated, the cells , solder joints etc. will be exposed to the elements which can lead to corrosion.

 I think the thing to do would be put it all together sealed up, then drill a small hole in one corner, flip the panel and drill another small hole in opposite corner. Flush the entire panel with nitrogen for a minute or two and immediatley fill the two holes with RTV silicone. That will stop the condensation.

 Happy building...

 David

[fungus]

I just had a thought; what about using silica dessicant sachets inside a sealed panel? You know the ones that come in packaging saying 'do not eat'..

Although I wonder how much they'd actually absorb..

[wayne]

David

I see the problem when I go too seal it now. I saw someone used Helium also to flush it out. There was a guy called Fred and used motor oil I remember some time ago. His web site is gone and seemed to cure all problems. There is so many pro's and con's with DIY's. The factory ones have no problems for 20 years. Seems most I have looked over work for a few years then trouble, from corrosion having it open to elements then sealed with condensation, maybe the motor oil might be better, does know his web site.

Thks

Wayne

[AbyssUnderground]

I had that idea a while back but I also wondered if it would work. Maybe someone can enlighten us with the answer :-)

[stop4stuff]

i'd always wondered that too...

experiment time

0.5g desicant silica gel + 2g water sealed in a cling film packet (wieght accurate to 0.01g). I don't know how long to leave it tho... i may have some sort of visual reference in 24 hrs.

back on topic...

mineral oil can be used inside a sealed panel (rather than auto oil)

[dogger2k]

you have to be careful with plexi glass, it can warp and expand at a different rate than the "u" chanel you put around it. You may end up with a panel that will warp in the sun. i have made a few pannels and the best one is with clear glass front and back. tha glass wont retain the heat. i use 1/4 x 1 aluminium flat bar (that i put a grove in for silicone) around the edges. I sealed it with some loose silica inside. dont forget to dry your silica before you seal it in there.

[Volvo farmer]

Dessicant is almost always installed in the frames of double pane windows. The aluminum box around the outside has little holes toward the inside space which let the dessicant soak up the moisture but the little beads can't get in between the glass panes.

I've had four 100W, 24V panels out in the weather now for several months, only two showing in this picture.

Anyway, I had a moisture problem in one of them, so I just drilled a little hole in the  top and bottom of the frame and the problem dissapeared. The other three are still sealed up with dessicant in the spacer, no moisture problems yet, though they seem easy to fix by just venting them.

Back when I did my project a couple of years ago, I tried to take what definitely worked and improve on it. So far, so good, though I only have four months of real-world testing out in the elements.

I know that I would not use plexiglass front and back until I found someone else who had used it with good results. Tempered glass and double-pane window channel has worked great for me so far and I based my design on someone else playing with these Evergreen seconds, back in the Ifred days, who used tempered glass in their design Sorry, can't remember who it at the monent. Maybe go searching stories back in the fall of 2004, that's when I was doing my reseach on how to build my panels.

[wayne]

Thanks Guys for all your input and nice Panels Volvo and hope they hold up. Last night I made a single cell 2 by 4" inclosed in Plex. This will be a test once it dry's for 48 hrs. Going to test extreme cold and heat. See if any problems and measure output. Then if all fails try oil and see if any loss and do the same thing. Another thought is to put reflective backing as not to heat up panel. Like to build that will last for years and be the same as bought ones. I found out plex does expand about 1/16" per 100f, so locking it down or U channel would cause problem over time. L channel would be better. We see

Wayne

[ghurd]

Someone had a homemade PV with plexi.

It bowed up... a lot.  Like it was pressurized.  There were photos but I can't find them.

G-

[wooferhound]

I made an anamorphic panel sandwiched between 2 pieces of glass  and sealed all the way around the edges except for two holes in the bottom and 2 holes in the top. The top holes were shielded by the roof of the house and the bottom holes were open totally but pointed down. The holes were about ½ inch square.





It was up for 8 years before i took it down 2 years ago when I moved. It has worked great all this time and showed no signs of corrosion or separation, just dust tracks from the airflow.

[Nothing40]

It probably was pressurised,if the panel was sealed.

The air inside would expand as it got heated up. ;-)

[wayne]

Hi

I got one box shipping from USA to Canada and was a broken mess. A warning if you order silicon make sure its wax dipped. Seem Customs like to play cards with these. Not happy with this. Will see what I can save and measure each piece. Now I wish I never started this but will use min cost for this panel.

Wayne

[Lust4PV]

Optically clear mineral oil like the kind used in the fermi lab accelerator (drakol 6?)might make a nice combo magnifier and moisture proof sealer. Google terms like "immersed solar cell" patents etc, m.i.t. types say 50 PERCENT more power.

mineral oil has been used as a liquid lense on slides for microscopes etc.

it could eliminate the optical losses from the cover glass, refractance = 1.52?

Most commercial glass outfits have a stack of mis measures in the back.

maybe leave space at top for oil expansion? I have had a test cell in a jar of mineral oil (fda laxative walgreens type) for a year (one of the ebay cells) no deterioration shows, other cell just moisture in air has pitted slightly, they are metal after all. oil specs are important ie moisture content, wax content,flamability etc.   Lust4PV

[wayne]

I did a single cell test in plex box, and measured with and without oil. I had greater power output with the oil vs with none. Have had temp drop to -20c and still seems okay. Think is acts like a lens but will it act like a coolent also. Not summer yet and  might try a small panel first. I would only fill 3/4 to leave for expansion etc. It would increase the weight of panel, but mine would be on ground level and maybe better for the wind anyhow. Seems no body has done this and long term effect on the silicon I don't know.

Wayne