After many hours of googling, I wanted to build a cheap panel to fit my requirements. I do not require a hailproof glass window for the cells, so I would not have to spend the extra money to protect the cells.
I came up with a simple cheap design. It probably won't last 25 years; it might not even last 5. But, considering the kind of conditions I set my panel in, it might just last quite a while. Anyways, I set this up to play with, not using it for serious power generation. I do charge my mobile devices with it though.
I live in a high rise apartment in Singapore, and it is summer all year long. The solar panel is set under a shelter with a shutter to protect it from rain. There is really no need for me to build those encapsulated or glass window panels.
So what did I use for my solar panel?
1. Polycrystalline ribbon solar cells. I used 3" x 6" cells (80mm x 150mm measured). You can get them from eBay. They come in many shapes and sizes. If I remember correctly, there is an instructable on solar cells.
2. Tabbing wire. They come in the solar panel kit. There are many resources on the internet for you to learn how to tab cells.
3. Bus wire. Part of the kit too. You use these to carry higher current.
4. Solder. I used a little bit of solder to connect the bus wires and tabbing wires together. Makes life a whole lot easier.
5. Flux pen. It helps to let the solder on the tabbing wire stick to the cells during soldering. Also part of the kit.
6. Glue. I used this to construct the backing of the panel.
7. Hot glue. Used it to glue some parts together. Used it to waterproof the connections.
8. Soldering Iron. Mine is rated 20W.
9. Pen knife.
10. Permanent marker.
12. Corrugated plastic. Used as backing for the panel.
13. Cling film, Cling wrap, whatever you call it.
16. Wires. Preferably 18AWG or below. Any expert on instructables please correct me if I'm wrong. If you use thin wire, you are going to lose a lot of power, or worst, start a fire.
17. A standard 12 volt barrel DC plug. Of course, you can use better ones like those shown in other instructables.
The construction of the panel was simple. I planned each and every step before starting to work on the panel; you won't make any mistakes if you follow your own detailed instructions. If you don't, you might snip off too much tabbing wire, solder the tabs wrongly, mess up electrical connections, etc. Please be patient and plan your panel.
My panel had only 12 cells. I'm planning to build another 2 panels of the same number of cells (why? read the end of the article). I placed them in a 4 x 3 configuration (you can see that white panel in the pictures).
I measured the length and width of each cell and multiplied the dimensions to get the size of the backing. Of course, you would have to add a little extra for the cells to fit in.
After that, I started tabbing the cells. The tabbing wires are already coated with solder. There are many youtube videos on how to tab the cells. Please take your time and tab carefully, otherwise you might just break them. Fortunately, I broke none:) Even if you do break them, as long as the break is not significant, you can continue tabbing them.
Test the cell voltage under sunlight or a powerful lamp using a multimeter. It should read about 0.5 volts or so. If you want to check current, put them under the sun and test using the correct range on your meter. The cells I got are rated for 3.6A of short circuit current.
After marking the dimensions on the corrugated plastic, cut them out using the knife. I cut out 3 pieces to create a 3 layer sandwich. I also alternated the "grains" of the corrugated plastic so that it would (hopefully) strengthen the board.
Glue the 3 layers together with glue(duh). I didn't use hot glue because hot glue solidifies too quickly. Instead, I used some general purpose adhesive. Try to avoid creating air pockets between the layers when you glue.
Place your tabbed cells on the board and check if it fits. Make any measurements if necessary. Take those cells away from the board and tab them to each other.
After tabbing, carefully place the cells onto the board. Cut a slot to let the bus wire go through to the back. Remember, be gentle.
When everything looks OK, use hot glue to tack the bus wires down. I didn't glue the cells to the board because I might replace it one day.
Hot glue the area around the slot where the bus wire exits the back of the board. Hopefully this prevents moisture from entering the front of the panel.
Now, wrap clingfilm around the board. Make sure you poke holes for the bus wire at the back. You can wrap as many layers as you like, but I'm not sure how it would affect its transparency. I only wrapped 1 layer.
Tape down the clingfilm at the back of the board.
Solder wires to the bus wires sticking out the back. Remember to check for polarity before you solder, so you know which color of wire to connect to.
Connect the wires to the DC plug.
And you are done! Test the panel out under full sun with a multimeter before using it. Make sure it reads the correct voltage and current.
Be VERY gentle with it. The cells are very fragile. Handle the panel by the edges and don't bend the panel.
Use it to power some small appliances. I used a voltage booster to boost it to 12 volts. Of course, if you build the full panel with 36 cells, you don't have to do that.
Why I built a 12 cell panel: As you can see, I am experimenting with alternative materials to build a solar panel. This design works only "indoors", because there is basically nothing protecting the solar cells except a thin sheet of cling film. I will use the rest of the 24 cells to build another 2 panels out of different materials to experiment. Expect to see an update soon.