Well I finally got round to making the solar panels. Here is the process.
These things are really fragile. You have to slide them apart as lifting the top one directly off the stack is enough to break it.
Once you have one off the stack, you apply the flux to the strips on the surface of the cell. Then solder the (precut) tabbing wire to the cell. No additional solder is needed.
40 of these later you have a stack of tabbed cells hopefully with none broken.
This is low iron glass which gives the highest efficiency for Solar panels.
On a commercial panel they lay down one sheet of EVA, then the Cells, then another layer of EVA then a sheet of Tedlar. I didn’t have the tedlar but this is used on the commercial panels from what I can tell to stop the EVA sticking to the vacuum press and for physical protection. As I won’t be using a vacuum press and it will be going straight onto my van I didn’t bother with the layer of Tedlar.
I made a little jig, which was simply a length of wood with an L shaped piece of plastic stuck to it. The back side of the cells are positive with the front being negative. You connect them much as you would a set of batteries with + on one cell going to negative on the next and so on.
this is the first string layed down.
I won’t bore you with pictures of each string being layed out. Here are all the strings layed out. You may not be able to tell but the are layed in alternating rows with the tabs sticking out on opposites sides on odd and even rows.
DISASTER!!!! I layed the second sheet of EVA on and started to heat it all with a hot air gun. Everything was going ok and it appeared to be sticking ok. I lifted the panel up to see how it was going on the other side and if I need to apply more heat. A certain person who shall remain nameless said that they couldn’t see so I lifted it up a little more and the top row of cells decided to go walk about pulling 2 further rows off the panel. This effectively brought the experiment to an end as the cells were destroyed and they couldn’t be separated out.
This happened because I was working from the center to the outside and the outer cells hadn’t been bonded yet. So a certain person who said “I told you so” didn’t really understand the full story. This was a failure of common sense not of materials or technique….
Would I do it again? Probably not. I live full time in a Motorhome so I don’t have enough space for projects like this. It is also fairly time consuming. From a financial point of view it would be worth it still. You could probably make a decent 140Watt panel for around £180. An 80Watt panel will cost you at minimum £150. So for an extra £30 you are getting an extra 60 watts. From a fun point of view. If you like interesting projects this is one that is well worth doing.
If you decide to take on this project I would either look for someone who has a vacuum press. Photographers sometimes own them for laminating images. If you don’t have access to one then use the QSIL method. QSIL will increase the cost by £30 but will make the project much easier to complete with less chances for disaster.