Once built the wind turbine to provide power during the windy days, it is time to make a system to meet power when the wind does not blow. The solar panel seems like an obvious choice to supplement the wind turbine. This is the reason because I have chosen to integrate the power from the wind with two solar panels into the roof of the Neverland structure.
I have started out the way I start every project, by looking for information on internet about diy solar panels. As mentioned before for the wind turbine, nowadays, there are a lot of guides and videos on internet about how to build a home-made solar panels. The windmills can be of different types, like vertical axis windmill or horizontal axis windmill, but the solar panels are in general the same, with a box for the array of solar cells and a glass above to protect them.
I have never tried to built a “diy” solar panel, but I think it could be possible even using common tools and inexpensive materials. Also the solar cells can be found as second hand or recycled material. The main problem is that the old cells have to be checked and this operation is for expert people, then I suggest to buy new solar cells indeed they are inexpensive and easy to find, furthermore they should be the only things to buy because the others materials, useful for the system, are easily to find as recycled materials.
The following picture (Figure 1) shows the solar panel how should be at the end of the work.
How they are made
First of all, we should consider the dimensions of the roof structure in order to install the two solar panels. There are two surface in the roof: the first one has the dimensions of 1×1 m, while the dimensions of the second one are 0,85×1 m. Since we have these surface I have thought that could be interesting build the panels to cover the whole roof with solar cells and then have as much as possible sun power relative to the area available. The following (Figure 2) picture is a drawing of the roof to understand how should appear at the end of the work.
The quantity of the solar cells to buy depends on the surface where we have to dispose them. After a little research on internet I have chosen to use a 6×6 inches (circa 16×16 cm) mono-crystalline solar cells. The total area of the roof is 1,85 meters square, so dividing by the surface of each cell (0,0256 meters square), we have the total number of the solar cells we need: 70 cells. Each cell produces about 0,5 Volt, so 70 cells in series would give about 35 Volts which would be good for charging two 12 Volt batteries. In the following picture (Figure 3) is shown an example of solar cell. Take note that they are very thin and fragile as glass, therefore they are easily damaged.
There are a lots of sizes of solar cells; you could choose larger or smaller cells for your panel, but the only important thing is that they have to be all the same size. Cells of the same size produce the same voltage no matter what type they are, while if you use different dimension of cells, the current will be limited by the smallest cell in the group and the larger cells will not work to their full potential.
The solar panels box are two shallow boxes. They could be made with a recycled wooden materials, I think it is very easy to find, probably you have them somewhere in your home. The dimensions of the two boxes, as mentioned before, are: 1×1 m and 1×0,85 m. In the following picture (Figure 4) are represented a simple scheme of the two panels. To protect the solar cells from the weather, the panel will have a plexiglass front, also glass could be used for this, but it is too fragile so I would avoid. Even the wooden parts of the panel should be protected from the action of the weather, so it is useful use a waterproof paint to protect them from water and moisture.
Once the wooden bases are complete it is time to make the solar cells ready. The first step is to solder and merge the cells. I read something about this operation and the best way to merge the cells is using a low-wattage soldering iron and fine rosen – core solder. Remember the cells are thin and delicate, if you push too hard, you will break the cells. The cells have to be soldered in series: the negative tabs from the top of one cell are soldered to the positive part on the bottom of the next. This connects the cells in series, and adds their voltages. The operation has to be done until you have a string of 6 cells then the whole process has to be repeated twelve times to get 12 strings of 6 cells for the two panels. Even the strings of cells need to be wired in series, so the strings must be staggered. In other words the second, fourth, sixth etc. strings must be rotated 180 degrees respect to the first, third etc. strings. To interconnect the strings of cells could be used copper braid, solar cell tabbing material or even regular wire. The operations mentioned before are shown in the next picture (Figure 5;Figure 6).
It is time to attach the cells in their box. In this step a tool is very useful: the silicone. There are many methods to merge the cells in the shallow box, but I think that the best is to place a small blob of silicone caulk in the centre of each cell. It is recommended do not use too much glue and do not glue the cells everywhere but only in the centres. The cells and the panel, once mounted, will expand, contract, flex and wrap with change in the temperature in the humidity. If you glue the cells too tightly to the substrate, they will crack in time while gluing them at only one point in the centre allows the cells to float freely on top of the substrate.
Each solar panel in a solar power system needs a blocking diode in series to prevent the panel from discharging your batteries at night or during cloudy weather. Once the strings of cells, the diode and all the connection are ready it is recommend to test the voltages and ampere of the system by ammeter as shown in the next picture (Figure 7).
If the system it is well connected and the test has a good results you can proceed with closing the solar panels with the plexiglass. The best way to attach the glass on the shalow box is to screw it and create an isolation around the frame with silicone to make a waterproof system. After some hours to dry the silicone the solar panels are ready to be mounted in the roof of Neverland structure. Finally should be add a polarized two-pin jones plug to the end of the panels wires. Mating female plug will be wired into the charge controller of the windmill system, so the solar panel can supplement its power production and battery charging capacity.
As in the past step I will write a table with a list of the things you need to build the solar panels (Table 1).