How do commercial panels eliminate moisture problems?

[somemathguy]

Hi, I got a 5lb box of the ebay cells a while ago but am still deciding what the best way to make the panels might be. I guess most people (including me) bought the ebay cells because the cost for a complete panel can be cut down to around $1-2cdn per watt if materials can be scavenged...in canada, the absolute minimum which you could buy panels retail for is about 7$/watt for larger panels (120W) or about 12$/watt for small non-amorphous panels (15W or less). From the discussions on this board, moisture problems in the home-built panels using the ebay cells seem to be the biggest technical problem...if a panel costs 2$/watt but only lasts 4 years before being destroyed by electrolytic corrosion, then you are actually spending much more $$$ than you would on a 7$/watt panel that is guaranteed for 20-25 years. There've been lots of proposed solutions including mineral oils, inert gas, sealing them up GOOD and hope for the best, or just plain leaving them open for ventilation - each with various problems and issues. It's hard to say how serious this moisture problem is going to be because nobody's ebay panels have been through an entire year of seasons yet...

Anyways, I've never heard of a commercial panel with moisture problems....how do they deal with this problem? As far as I've read, they are constructed in very clean environments - perhaps the air is moisture-controlled in the factory during construction? I did examine one commercial panel to see what i could learn - it was constructed with a white PVC backing material and a thin glass front, framed with aluminum. The space between cells and glass was negligible...in fact it looks like the cells are touching the glass. Also, the cells themselves have just a tiny space around them...less than 1/8" between cells. It seems to me that if you reduce the volume of air inside the cell this much, there is little air to cause moisture problems. This panel did not appear to be sealed with EVA or something similar, just sturdily constructed providing no place for moist air to accumulate and cause condensation.

Someone on this board made a lot of panels out of plywood and simply put sticky transparent plastic right over the cells on top of the plywood...with no moisture problems yet, presumably because there is no space for moisture to accumulate. Maybe we should follow his lead?

[ghurd]

Some of them at, least 2 brands, are solid. No place for air or moisture.

G-

[sandovalch]

I've made my panels with plywood backing, commercial glass in front of them and aluminum framing and had no major moisture problems. I left the back of the panel open, I even am trying to get more air to circulate inside of them. For me the problem is not that much moisture for now, but heat. I did not want to put holes in the back of the panel, but now I'm trying it with some of them.
We've had no major rain here so I couldn't tell if moisture is going to be a problem. My panels are constructed in a way that moisture won't get in, at least not from rain drops and hopefully the moisture will evaporate throught the heat again.
Tell you when it happens.

[pyrocasto]

Moisture will definantly get in through any hole, just maybe not a droplet of water or such.  I almost built my panel thicker to pump air through it, and use the heated air for my house.

[Tyler883]

One gentleman on a different thread talked about sealing the unit,

leaving a tiny hole on each end of it,

then flushing the air out by pumping anything like helium into the enclosure,

then of course sealing the two holes with silicone.

This could be repeated on an annual basis, if you like.

He claimed that many window manufacturers use this method, seems reasonable to me.

[pyrocasto]

It's been discussed, but you have to be careful what you use. Some stuff wont transfer heat well I dont think. Some will expand and contract more, and some can corrode your cells or wires.

[Jeff7]

They used PVC as a backing? Kind of surprising, at least to me, as this seems like it would tend to insulate the cells and cause excessive heat buildup. I was looking at aluminum as a backing. Obvious drawback of this of course is the expense - I'll have to see if I can price out something else though. The cells should be able to withstand the high temperatures; I'd just worry about the rest of a homemade panel not holding up to the hot air inside.

Granted though, I don't know exactly how well PVC transmits heat; as a plastic though, I can't imagine that it does a very good job of it.

Oh, this plastic backing - do you happen to remember how thick the backing was?