Resin?

[Zipster]

Hi there,

I have started to build a 72 cell panel. I have my backing made, the perspex and the cells all soldered. I am now looking for a good resin type that will last for years without going yellow or crack. Can you help?

I will proceed to a back encapsulation: Line the cells onto the backing plate, use glue to make them nice and flat then pour a layer of resin that just covers all the bumps, let it dry, then add another layer before applying the perspex on top, one end first then lower the other end slowly to avoid any bubble.

I have not seen this technique anywhere so I will make a small test with some off cuts first.

z.

[stl-outlaw]

I am also wanting to go this route with my first solar panel. I am planning on the same method except I plan on using a tape to secure the cells directly to the glass and tape all outer edges and contacts in between, then finish up the backside with a epoxy resin such as "CLR-HP A/B" as seen in the tutorial http://www.youtube.com/user/GREENPOW.../8/0UM3DgyG_BQ , I'm going to use a aluminum frame though. I have been researching solar information for months now trying to prepare for my first build and I guess the reason why people dont use just backside encapsulation is due to the small amount of air that would be placed in front of the cell, but at the same time I dont want to use full encapsulation because I dont want any kind of blockage of the cells and people always seem to have trouble with air bubbles. I am in no way a solar expert or even close but I will post my results of my panel as soon as it's complete.

[russ]

For good information on DIY check the following links.

The green power site has all sorts of flaky stuff on it as I remember - hho etc - when a site lists that type of stuff I never go there.

http://fieldlines.com/board/index.php/topic,144982.0.html

http://fieldlines.com/board/index.php/topic,144995.0.html

http://fieldlines.com/board/index.php/topic,145004.0.html

[stl-outlaw]

Thanks for the links, good information. What would be your opinion on taping the cells to the glass as to not let the sylgard penetrate to the front of the cells and then creating a dam of sorts around the outside parameter to help hold the sylgard only to the back of the cells ? Would you think this would be strong enough for a 36 6x6 panel measuring roughly 30x60 ? I've ordered my sylgard and the CLR-HP A/B with intentions on using both but would like some professional advice first before jumping in. You hear so many different opinions that it's hard to pick which route to take so I guess in the end you almost have to just do it and find out for yourself. Thanks in advance !

[Mike90250]

1) I don't build panels. It's a dead end for the time and $ wasted on them.

Thermal expansion. You must allow for it, or the cells will be torn apart

Stiffness. Cells must be supported rigidly, bending will break them.

Heat Dissapiation Air is a lousy thermal conductor, factory cells use a material to bond the cells to the front glass to help dissipate the heat.

[Zipster]

@stl-outlaw: How are you are going to use tape if you are back encapsulating? The front of the cells will be face up... Unless its double side tape I dont see how you'd do that. You must be front encapsulating otherwise i'm confused here.. So you say CLR-HP A/B, where can I find this? Normal hardware store or specialist? I'm in Australia BTW.

@Russ: All your links are referring to EVA, I'm not using any of that stuff on this project, thanks for that Greenpowerscience link I have seen the whole series already and they are interesting.. Meanwhile, its about front encaps so no complete use for me.

@Mike90250: Do you have anything more constructive to say? I think having the skill of being able to build my own panels is definitely relevant, even if my plan is to possibly buy them cheap from china if I run out of time. Do you have any story of failure you want to share?

.z

[stl-outlaw]

My plan was to place glass into frame like normal, then lay down strings of cells and solder them together, then using a clear shipping tape that would be purchased at "UPS" or "Office Max" to tape the cells directly to the glass covering all bus lines and connections and outer edges of all cells, basically sealing the cells to the glass so when the epoxy is poured onto cells it will prevent it from creeping in front of the cells. It sounded like a pretty good idea when I saw it because of the "yellowing" that can happen with UV exposure to sun with epoxy and also I like the idea of not having anything in front of cells to block any UV transmission at all.
I called it "back encapsulation" because the epoxy would only be in contact with the backside or positive side of cell and wouldnt contact the blue or negative side of cell in any way due to the tape sealing the cells and connections to the glass. I could be wrong on that I'm not sure but that was what I thought it would be referred to.
The only thing I have reservations on as far as the whole epoxy thing goes is the "expansion" of the cells under heat, but from what I understand the "CLR-HP" cures similar to slygard but I dont know this for sure yet because I havent tried it yet. I also purchased the epoxy from the internet on "ebay" and the seller was "polymerproducts", price was only $25 and another $16 for shipping.
I just received the epoxy yesterday so I'll let you know how it turns out when I get it finished , I think I might try it on a small panel and see how it goes. Like I said before I'm new to the solar scene and have no prior solar panel building experience whatsoever.

The most logical solution to the whole solar panel encapsulation really does seem to be the "slygard" route, but the only thing that bothers me with that is the bubbles that almost every single person complains about for the end result. If it was not for that I would go that route for sure.

[Mike90250]

@Mike90250: Do you have anything more constructive to say? I think having the skill of being able to build my own panels is definitely relevant, even if my plan is to possibly buy them cheap from china if I run out of time. Do you have any story of failure you want to share?

Asking the right questions, providing the answers to questions folks don't know to ask, and correcting the many "just wrong" assumptions, IS constructive. IF I get the info to folks BEFORE they have spent a boatload of $ to take their house off grid with one DIY panel.

Failures all over here.

[Zipster]

@stl-outlaw: Sticky tape onto the glass? I guess you are saying that you will tape the strips together and the tape will not be directly on the glass, like on the greenpowerscience video. I would personally not worry about the slight yellow tinge of the resin being in front of the cells as it would be only a fraction of a mil. This is ny first solar panel as well, I'm glad we can share our results. My encapsulation went fine, no bubbles, due to the low viscosity of the resin probably. Finishing the framing when I get a chance, and we'll see how it goes after a week in the hot sun.

@Mike90250: A solar panel fire caused by expanding materials? Can you be more specific on that mate

[Mike90250]

....
@Mike90250: A solar panel fire caused by expanding materials? Can you be more specific on that mate

I don't know the exact cause, but as cells move ( expand/contract day/night) the tab wire has to take up the flex. If not designed right, too little wire and it cracks instead of bending. Arcs at the crack. heat. plastic and wood = fire.

[Zipster]

Theoretically the wires have more tensile ratio than the surrounding expanding materials and thus have a coefficient of expansion too but why not, expansion could have provoked arcs. In short if I get all the expansion coefficients of materials and work around that I should be out of trouble right?

[Mike90250]

Getting the materials matched will go a good ways to increase the relibality

[russ]

Theoretically the wires have more tensile ratio than the surrounding expanding materials and thus have a coefficient of expansion too but why not, expansion could have provoked arcs. In short if I get all the expansion coefficients of materials and work around that I should be out of trouble right?

As you will not get that information I guess you are stuck - Cells on Ebay you are going to ask for component specs? Good luck as it won't happen.

[Zipster]

Cells are made of 100% silicon crystals, they have their exp coefs very close to glass. My only worry is to find the ones for epoxy but in any case I still can work it out myself via tests. Or maybe someone in here knows about it that would save me time..

[digimart]

Stl-Oulaw & Zipster,

How did things for both of you ? Please post your feedbacks.

Thanks