Solar energy is the coolest energy source in the world. But because of its cost of energy harvesting systems, it’s not very popular among a lot of people. However, while I was looking for some cheap option for a DIY solar system, I found some sellers on eBay, selling solar cells for considerably lower prices. So after careful consideration, I ordered 100 pieces of solar cells, which cost me a 8.38$ with free shipping. It was branded as AIYIMA 100pcs Solar Panel Solar Cells. However, it’s specification says one cell provide 0.5V 320mA of current with an efficiency of 17.4%. And with that specification I could have maximum of 16W (0.5Vx320mA) from all of the cells combined together. Which isn’t much, but since 0.5$ per a watt is really a cheaper option for me. I’ll add a link below the post to eBay seller if anyone needs to take a look.
In a few weeks I received it with a well protected package including nothing but 105 solar cells. I had to check several of them to make sure they are working and all of them was given me an acceptable result.
Once I had satisfied with cells I had to decide what kind of panel I had to make. After a quick research I found for 12V system I had to make a Panel with peak voltage around 18V and for a 24V system, it’s going up to 36V. The reason behind that is, when a load is connected to the panel, voltage is going to drop as our setup. The more current draw from the load, the more voltage drop is occurring depends on various factors. At least if I am going to charge 12V or 24V battery for storing energy, I need a larger voltage than battery voltage for make it work.
In my situation, I went for 24V system for oblivious reasons. First one is preventing energy lost while transferring. Second one is I have planned to use inverter which work with 24V. The first reason is valid for everyone and in every system, unless if you use bigger wires or something. If you transfer the same amount of energy through wire in different voltage, According to P=IV, lower the voltage, current become higher and because of resistance of wire most of energy become a heated and lost way through the battery. So prevent that happening, we can use wires with lowest resistant, which is thick wires. Or use higher voltage to lower the current which is more likely less energy wasted as heat. In that way we can use thin wires which is more cost effective.
Here are 2 panel systems I planned. For 12V, Its use 36 cells in parallel to create around 18V. And for 24V system, it should be used 72 cells in parallel to get around 36V.
First, I had to solder each cell for connecting them each other. I used, excess pins from LED’s for my previous project for connecting each cell. However, in this process I had to scratch the back side of welding tape a bit of a make surface more appealing to soldering.
However to finish this process you might need tons of patience because of cells are very fragile, you most likely broke every one of them in this process. In my case I broke 20 of cells before the work done. So this might not be very cheap after all. But after a few practice rounds it can handleeasily without breaking.
After prepare 4 of 18 cell panels I used a plain glass to mount them using glue and connect them together for complete the panel.
In testing I was able to get 40V max in direct sunlight average to 38V. To be honest, I wasn’t expecting that much result from it. However, when I connect to load which is 12V DC cooling fan with 0.15A rating on it, the voltage drops 17.6V max to 3.6 V min depend on light intensity of the sun. But at the end, I could able to run that cooling fan with a maximum speed (I guess) without paying any electricity bills.
These cells are working and provide sufficient power for small scale projects. But preparing these cells is very hard. However, I’m planning to go for complete system with batteries, charger, controller and so on, and then I’ll be able to tell whether this cell are cost effective than commercial products or not. Then I can accurately calculate the maximum power they can provide and hopefully I will do that soon.