Encapsulating with EVA

[conntaxman]

eva

http://cgi.ebay.com/1m-10m-Solar-Pan...item1e60e9be3f

why is this stuff so expensive? $15 per square meter?

Is it just thick plastic?

=======================
rolland .I agree,cost too much.But now dosen't everything.Watching that vid, I cant figure how he hooked up the vacuum cleaner to the Bottom side of the eva.Because he didn't have that in a vacuum Bag.I know he said he drilled a hole in the bottom of the table.
Im going to start to make my "autocave" I guess that is what they call it.It's a box that i'll beable to put a bag with a vacuum line going to it and also I can add pressure to the inside of the box and also have heat source in it to bring it to about 150 deg.. One guy here use a comercial one and he said it worked out pretty good.My box will be big enough for a 36 cell panel. Hope it works.
John
I made one panel using Surf Board epoxy , the company said that in FL., that is what they use. Up here it's not good, because of the cold ,below 32.It cracks. Well it's a learning curve. lol

[rollandelliott]

where to get tedlar?

http://cgi.ebay.com/1m-10m-Solar-Panels-Cells-Tedlar-backsheet-TPE-DIY-/130474950207?pt=LH_DefaultDomain_0&hash=item1e60e9be3f

why is this stuff so expensive? $15 per square meter?

Is it just thick plastic?

[rollandelliott]

this is what I'm going to try.

http://www.youtube.com/watch?v=QD5SYrubR_E&feature=player_embedded

He uses a heat gun, but that sounds slow and ineffcient.
I think a piece of sheet aluminum on top with bathroom floor heating strips would work great.

http://cgi.ebay.com/13-Sq-ft-120-Volt-Electric-Floor-Radiant-Heating-System-/330367265974?pt=LH_DefaultDomain_2&hash=item4ceb6c6cb6

http://www.briskheat.com/p-152-rh-plastic-bending-strip-heater.aspx

Yeah the heating wire is expensive but I actually have some already cause I'm gonna heat my bathroom floor latter on.

Also to put pressure on the top to the cells and help drive out and seal the membranes I have a 1/4" thick piece of foam sheeting that is used with perforated laminated plastic. I used to laminated photographic canvas and the sponge helps helps squeeze out any air spaces and acts as a leveling agent. I'll let you know in a few months if my plans worked out.

[conntaxman]

EVA vs Sylgard

May be or hope some one could let me know about these spec. for using this to cover the face of solar cells when making a panel.This would be in place of layer of eva on the blue side of the cell.
---------------------------Good or Bad
Visible Light Transmittance 86%

Total Solar Transmittance 74%

Total Solar Reflectance 8%

Total Solar Absorbance 18%

Visible Light Reflectance 10%

Winter U-Value 1%

UV Rejected 99%

Shading Coefficient 92%

Total Solar Energy Rejected 20%
............................
This would ease my mind alot, and save me money on wasted cells.
Thanks
John

[conntaxman]

vacuum

if you are using 2 hot plates to heat the entire panel, you have to rely on the air inside to move the heat around. if you vacuum first, you will only melt 2 spots. (at each hotplate)

Try it on a sample first. We freeze and bake stuff all the time here at work, and with huge 20x30' Ln2 cold plates and electrical heaters, it takes hours to change the temps in a vacuum chamber, when there is no air, it's real slow.

.
Hello mike. I have been looking all over net and wacthing vid's of sealing solar panels.not much help. But like you said hear first them vacuum.
I didn't get my EVA yet,so don't know what it looks like.
Im trying to figure out the steps to do this. would this be correct.Put glass down,then EVA,then cells,then EVA.next heat to about 120 to 150 degrees,next turn on vacuum.
Now if that is correct when do I put on the backing? I plan to use some kind of plastic, or if I could use "window security Film" here is the website http://www.geowindowfilms.com/clear4mil.php
But I dont know if the EVA will Stick to it.
Let me know if you think the sept's are in order.
Thanks. { But I NEVER though about heating it up with No air in the box]ha ha ha .
John

[conntaxman]

vacuum

if you are using 2 hot plates to heat the entire panel, you have to rely on the air inside to move the heat around. if you vacuum first, you will only melt 2 spots. (at each hotplate)

Try it on a sample first. We freeze and bake stuff all the time here at work, and with huge 20x30' Ln2 cold plates and electrical heaters, it takes hours to change the temps in a vacuum chamber, when there is no air, it's real slow.

.
Hi mike , I never though about NO AIR when heating. My box will be only the most 4foot long x 4foot wide x 5 inches tall.

[Mike90250]

if you are using 2 hot plates to heat the entire panel, you have to rely on the air inside to move the heat around. if you vacuum first, you will only melt 2 spots. (at each hotplate)

Try it on a sample first. We freeze and bake stuff all the time here at work, and with huge 20x30' Ln2 cold plates and electrical heaters, it takes hours to change the temps in a vacuum chamber, when there is no air, it's real slow.

[conntaxman]

Heat layup

Heat that layup up BEFORE you pull the vacuum. Pull vacuum slowly, to let parts adjust, or you will crack all the cells. Vacuum conducts NO heat (thermos bottle) so heat & get it all melty before you vacuum.

Mike have you ever done a panel like this before?This sound backwards to me.wouldn't it be harder to remove the air if this eva is melting and sticking together,What would happpen if I pulled a vacuum first? and then I still have to find out how much of a vacuum on a gague.
tks for your reply
John
I just dont want to screw it up, cost too much.

[Mike90250]

Heat that layup up BEFORE you pull the vacuum. Pull vacuum slowly, to let parts adjust, or you will crack all the cells. Vacuum conducts NO heat (thermos bottle) so heat & get it all melty before you vacuum.

[conntaxman]

eva/vacuum

The Teddar is bonded to the backs of the solar cells with a sheet of EVA. The EVA bonds when it is heated. Commercially this is done with a vacuum press. If you don't have access to a press you might apply pressure with two aluminum sheets clamped together and heated in an oven. You would have to be careful to get even preasure and not to break the glass. The tough part will be to ensure you get no air bubbles without a vacuum.

.
I have a question.I ordered some eva , Im making 36 cell panels. Im trying for figure out how this eva works.I guess their is a sticky side to it. Now I know that you have to heat it up to bond it together. Im going to build a Box large enough to put in the solar panel.Say 35Lx35W x12 high with an heating element in it,and also a connection for a vacuum pump. Would i first put the glass down then the eva sticky side to the glass,then the face down of the cells onto the eva and then next peice of eva not the sticky side on to the back of the cells,then a back sheet will say of plastic. Now put this in the box and pull a vacuum on it to remove the air,then turn on the heat to about 150 degrees as you mentioned. let it stay in their for about 30 min. DON'T know the time for the heating part. Last let it cool. and then remove it.
would that work?? Please correct me if any part is wrong.
thanks John

[Sandman57]

It is possible to get a vacuum bag that size though it may be difficult to find material for a "one off" project. Vacuum bag material generally is sold on rolls 52" or sometimes 60" wide. To make a 52" x 96" bag you would roll out 194" of 60" wide material, fold it over and use vacuum sealing tape around the edges to make a bag slightly bigger than the your 52"x96" panel.

Without vacuum sealing you might be able to get the Tedlar to stick to partially cured encapsulant. The purpose of Tedlar is to seal up the back of the panel with a weather resistant material. Most folks seem to have good luck with the liquid encasulate so the Tedlar may be unnecessary if you go the liquid route vs EVA

[Tazman]

Thanks

Thanks for the reply. I guess I am out of luck. My panel is 52" x 96".
Do you think the liquid encapsulating might work with enough pressure evenly applied as it dries?
I have made several panels of increasing level of professional look. This one has an aluminum frame with the liquid encapsulation (took 4 jars). So far cost about $350 CAD so I figure it's a good deal if I can get it to last.

Is it possible to buy a vacuum bag of that size?
Cheers

[Sandman57]

The Teddar is bonded to the backs of the solar cells with a sheet of EVA. The EVA bonds when it is heated. Commercially this is done with a vacuum press. If you don't have access to a press you might apply pressure with two aluminum sheets clamped together and heated in an oven. You would have to be careful to get even preasure and not to break the glass. The tough part will be to ensure you get no air bubbles without a vacuum.

[Tazman]

New question

Can this be done without the autoclave? I have the Tedlar (TCP) but no info on how to apply it.

[Sandman57]

In the process I used a vacuum pump sucks all the air out of the bag and forces eva and cells against the glass. The difference between inside the bag and outside air preasure creates this force. When I put the laminate into an autoclave and increase the pressure outside the bag the force on the laminate increases because the differential between inside and out increases. At 15psi I shut off the vaccum pump and open the inside of the bag to outside the autoclave. The 15psi presure creates sufficient laminating forces and "venting" the bag ensures that if there are any small leaks in the bag the preasure inside and out won't equalize causing the bag to stop pressing down on the laminate. This is a common technique for building composite laminates. Preasure is preferable to vacuum because any air bubles in epoxy resin will enlarge under vacuum and shrink under pressure.

I used to work as a boat builder and have access to a large autoclave that is used to create carbon fiber hulls, masts, and components. When they fire up the autoclave they don't mind me putting a pannel in with a boat parts.