Most people who get serious about prepping end up adding some sort of alternate power system to their homes eventually, usually solar power. Solar is abundant and doesn’t require any fuel, which is a real advantage in a post-disaster world. But the solar panels themselves are very expensive, especially if you consider trying to buy enough of them to go off-grid and power everything in your home.
But you can save about half the cost of solar panels, if you build your own. This is actually not all that difficult, although it is rather tedious. The only special skill you need, besides the ability to work carefully so that you don’t break the solar cells, is to know how to solder electronics.
A Note About the Electronics
A solar panel consists of a number of cells, all connected together electrically and mounted together in a sealed, glass fronted frame. Typically, 36 cells are used, to give an output voltage of 18 volts. Each solar cell produces 0.5 volts, regardless of size, hence the 36 cell total. The difference that the size of the solar cell makes, is that larger cells produce more watts of power than smaller ones do, even thought he voltage is the same.
There are two different ways of connecting solar cells together, both of which will end up being used to make a complete solar power system:
- Connecting in series – This means that the positive end of one solar cell is connected to the negative end of the next one in line, much like batteries in a flashlight are connected together. When we connect in series, the voltage is added, but the wattage stays the same.
- Connecting in parallel – This means that the positive ends of all the solar cells are connected together and the negative ends are all connected together. When we connect in parallel, the wattage is added, but the voltage stays the same.
Individual solar cells, like batteries, have a positive side and a negative side. The front of the cell, which is usually colored blue, is the negative side. The silver lines running through it are electrical contacts, where the electricity that the cell is producing is gathered, allowing you to connect the cell to others. The back side, which is usually grey is the positive side. This side will have some “pads” on it, which are the electrical contacts.
Connecting the Cells Electrically
To start with, wires, known as “tabbing wires” need to be soldered to each solar cell. Tabbing wire is a very thin, 2mm wide wire, which is pre-tinned. This means that it is coated in electrical solder. The silver lines on the front side of the solar cell are tinned as well. So, pieces of the tabbing wire that are twice the width of the cell need to be cut and soldered to the major leads on the front side of the cell. The major leads are obvious, because they are thicker.
The solar cell in the picture is a 3”x 6” cell, which is pretty typical for a homemade solar panel. As you can see, the tabbing wires go the full length of the major contact on the cell and extend beyond it by the width of the adjacent cell. The big socket in the picture is just there as a weight to hold the tabbing wire while it is being soldered.
Once you have all 36 cells tabbed, it’s time to connect them together, making strings of solar cells. With 3”x 6” solar cells, strings of nine cells work well. You’ll need four strings for each solar panel.
To make the strings, the solar cells are laid upside-down, with the tabbing wires from one cell overlapping the neighboring cell, as shown in the photo above. Then the tabbing wire is soldered to the pads on the backside of the cells. Notice how little space there is between the cells. Extra space is just wasted space; you’re better off keeping them close together. The stick on the right is there just to keep the string of cells straight.
The four strings of nine cells will need to be mounted, side by side, to a backboard for the solar panel. This backboard can be made out of thin plywood or plastic. If you use plywood, give it several coats of paint, especially on the edges, to make it waterproof. The easiest way to mount the cells, is to put a dollop of silicone caulking on the panel at each cell’s location, and gently press the cells down into it.
Remember, solar cells are thin glass, so they break very easily. So when I say gently, I really mean it. You have to treat these extremely gentle at all times. But even if you break them, they can still be used. As long as the cell is somewhat intact, it will still produce power.
When you attach the cells to the backing board, you want to do it head to toe. The positive end of one string needs to be sitting next to the negative end of the next string. That’s because the next thing you’re going to do is attach the strings together electrically, making one long string out of them.
In this diagram, you see the panels laid out, as mentioned above, with the positive and negative ends of the strings alternating. These are then connected together with buss wire, which is like tabbing wire, just wider, as shown by the thick black lines. The positive end of the string is in the upper-right-hand corner and the negative end is in the lower-right-hand corner. Regular zip wire will need to be attached to these locations and run out of the panel, to connect it to whatever you are going to power with it.
Building the Frame
At this point, you should have a functional solar panel. If you put it in bright sunlight, it should produce 18 volts. But it’s not real safe to leave it out in the sun, as rain could damage it, let alone hail. So, we need to mount it into a frame.
This can be done a number of different ways, even a glass-fronted picture frame will work, as long as it is big enough, and the glass doesn’t touch the solar cells. You can also buy frames specially made for building your own solar panels. While those work well, unless you get a really good price on them, it kind of defeats the purpose of building the solar panels yourself to save money.
Probably the easiest way to protect your solar panel is to make a frame out of ½” aluminum C channel. You can buy this at your local hardware store or home improvement center. You can also buy it online at www.OnlineMetals.com. If you are going to make several panels, I’d recommend going this route.
Since the backboard provides structural integrity, all you really need to do with the frame is hold the glass in place and seal the edges to prevent water from getting in. I’d recommend using tempered glass for your solar panel, as that is stronger, yet won’t become foggy from exposure to the sunlight, like some plastics will.
Attach the glass directly to the backboard with double-sided foam tape. You might need two layers of the tape, to ensure that the glass doesn’t touch the solar cells themselves. Align the glass carefully, before allowing it to make contact with the adhesive.
In order to seal the assembly, start by cutting pieces of the aluminum C channel, mitering the corners so that it will connect together, making a frame. These can then be glued to the edges of the panel with silicone caulking, holding them together with masking tape until the caulking dries. Double check all the way around, to ensure that there are no gaps in the caulking, where moisture might be able to seep in.
There you have it. All you need to do is mount your solar panel and connect it electrically. You’ll probably want to make some more too, so that you can generate more electric power. It takes a lot of solar panels to give you the power that you’re ultimately going to need.