Moving right along from
http://fieldlines.com/board/index.php/topic,144982.msg982556.html#new ( part1), we now have an oven to cook the panel in.... we have bought the vacuum pump, and are now prepared to make a test panel/cell..... just to see if it is true.
I decided that it would be best to do a show and tell for a single cell at this point, in a step by step approach.
So here we go:
First get a piece of glass that will fit your cell on.
Wash/dry the glass with alcohol (Methylated spirits).
Grab the bit of your EVA your going to use, I have chosen to build a single 6x3 cell, with some other bits thrown in just to give an interspace between cell and cell bits..... like this:
Next throw on the top EVA piece:
Now a piece of tedlar, or (tyvec I used here) anything you want the rear of the cells to wear. It must be non-porous, rot proof, water proof and everything else proof. It only performs the role of keeping the EVA away from anything that may want to harm it.
The EVA sets a bit like silicon. It is very rubbery, and not especially strong..... although try getting it off the glass once crosslinked properly and you may decide that it is very strong.
Here we are with a piece of tyvec on the back
Now we have all the ingredients to make it work, we just need something to allow the vacuum to suck the air through..... an air wick if you will. This can be any porous material you can get hold of. I find for small 60watt panels, that a few thick teatowels covering the back do ok, for bigger panels, it is best to find something a bit better.... beach towels? Glass matting would be good if you have it, I tried shade cloth on the 2mx1m panel, but found that it shrinks a little when it gets heated. Not enough to damage anything, but enough to make the cells not line up as I had placed them. For this show and tell I just folded up a rag that was lying around near me... and so you get this:
Next we need a plastic bag big enough to place our panel in. Unless your into building big ones like i have, most likely a big garbage bag will be the best for the job... cheap, plentiful, and plenty strong enough for the job. Here I used a transparent one for demonstration of seeing the stuff in the bag
Next we poke a hose into the bag and seal it up I use plastic wire ties. This seems to hold the bag opening onto the vac hose pretty well.... except tor this time. The plastic bag must have a hole in it, as I could not get down to max vacuum......
Do NOT place the rubber suction hose over a cell. It would crack that cell, so just place it between your airwick material and the glass... or inside the folds of the material, but away from the cells themselves, and let it suck from there. Provided there are no leaks, it will all eventually seep through the wick. If there is a tiny leak, your wick will need to be very porous to still work. If it is a bit difficult for the air to move through, a leak will kill this project.... if it is a very free wick material, a leak may be tolerated.... best without though.
So I have replaced the clear leaky bag with a trusty black garbage bag....
Note the wire ties:
Now for this exercise I won't use the big oven, but instead will show just how simple this can be.......
Here is the latest you beaut high tech laminating machine...... or the 1 minute oven..... and it will work every bit as well as an expensive laminator
Of course we know there is more to it than this ......like the heater.
For this size ... and up to at least a 60W panel, a fan heater pinched straight from the loungeroom would do to get it up to 80-100C..... or if you wanted to prove a point, perhaps broil it in boiling water.....ie half a 44 gallon drum parked over the camp fire........simmer till cooked.
This does not need to be high tech is what I'm getting at, to get a perfect result.... just temp and time.
If you are going with very low temp, then it will take a very long time... ie 80C for 80 minutes, or 140c for 5-10mins
I have toyed with the idea of using the sun... ie use the some of my spare solar glass from the hot water heaters, and make a solar oven... very similar to the solar panel itself... as the oven.... I haven't tried it as yet, but if you can boil water on a hot day with a sheet of glass and the black backing..... then , it can crosslink the EVA easily too.
Your trial one will give you an idea of how long to cook it with what equipment you have to get your brand of EVA it to crosslink properly and stick to the glass VERY well. If it has not been left for long enough, you will be able to peel it off the glass, simply put it back in and cook some more... noting how many minutes gets the required bonding...
Our trial one looks like this
and the whole sophisticated arrangement looks like this:
And yes, it got to .....and stabilized at about 112c... so I cooked it for 45mins anyway. Note the improved insulation (brown towel) pushed the temp up another 20 degrees from the picture first showing the box oven
I don't think you can overdo the time on these low temp crosslinking exercises, although it is probably worthwhile exercise to use a normal cooking oven with a good thermostat to get an accurate picture of how the stuff bonds to the glass... how long for how well. That is the only critical figure in all of this.... and even then you can always put it back in the oven without any problems at all.
And here is what we have got ourselves.:
So it does work, and it is dead simple, and very easy to get right, and very forgiving if you dont..... stick it in for longer...
The only difference to doing this size
or this size:
is how much time you have, how many cells you have, and how much glass you can scrounge up
..............oztules
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