I encapsulated my first panel today with EVA and Tedlar. I soldered up 36 1.5v 3x6 cells to get a 60watt panel. I have access to a vacuum pump and autoclave so I wanted to see if I could do a profesional grade encapsulation. The laminate was stacked as follows:
2. EVA sheet
3. Solar cells
4. EVA sheet
5. Tedlar Backing
The laminate was placed in a vacuum bag and the pump drew a 27hg vacuum. This sucks all the air out of the bag and squeezes the laminate together.
The bag was placed in an autoclave and heated to 175 deg and pressurized. When the pressure got to 15psi the bag was vented and the preasure was increased to 20psi (i.e. 20psi outside the bag, one atmosphere inside the bag) and was left for 20 min. Pressure is preferable to vacuum becasue any air inside the bag is compressed though the vacuum pump should remove 99.9% of the air.
I wasn't sure what the correct pressure should have been but I was nervous about the glass cracking or the cells splitting so I didn't increase it any further. I let autoclave cool to 135 and then removed the laminate.
This process seemed to work well. The cells are flat against the glass with no air bubles. The EVA seems to cure clear and bonds the cells to the glass and the Tedlar to the back. Tedlar is an opaque smooth plastic sheet that should keep moisture from migrating through the EVA and into the panel.
The only thing I will do different next time is to let the pannel fully cool before removing the panel and possibly leaving the panel in longer at the max temp. I think taking the panel out at 135 degrees the EVA isn't fully cured and might be susceptible to delaminating.
Anyone out there know what temp/preasure/time the factories use with their laminating tables?