Several years ago I bought some remote property in Arizona. I am an astronomer and wanted a place to practice my hobby far away from the terrible light pollution found near cities of any real size. I found a great piece of property. The problem is, it's so remote that there is no electric service available. That's not really a problem. No electricity equals no light pollution. However, it would be nice to have at least a little electricity, since so much of life in the 21st century is dependent on it.
I built a wind turbine to provide some power on the remote property (will be another instructable in the future). It works great, when the wind blows. However, I wanted more power, and more dependable power. The wind seems to blow all the time on my property, except when I really need it too. I do get well over 300 sunny days a year on the property though, so solar power seems like the obvious choice to supplement the wind turbine. Solar panels are very expensive though. So I decided to try my hand at building my own. I used common tools and inexpensive and easy to acquire materials to build a solar panel that rivals commercial panels in power production, but completely blows them away in price. Read on for step by step instructions on how I did it.
You can learn more about this project and my other alternative energy projects, including my home-built 15 Watt solar panel, my home-made wind turbine, and my biomass gasifier on my web site.
I built a wind turbine to provide some power on the remote property (will be another instructable in the future). It works great, when the wind blows. However, I wanted more power, and more dependable power. The wind seems to blow all the time on my property, except when I really need it too. I do get well over 300 sunny days a year on the property though, so solar power seems like the obvious choice to supplement the wind turbine. Solar panels are very expensive though. So I decided to try my hand at building my own. I used common tools and inexpensive and easy to acquire materials to build a solar panel that rivals commercial panels in power production, but completely blows them away in price. Read on for step by step instructions on how I did it.
You can learn more about this project and my other alternative energy projects, including my home-built 15 Watt solar panel, my home-made wind turbine, and my biomass gasifier on my web site.
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Signing UpStep 1: Buy some solar cells
I bought a couple of bricks of 3 X 6 mono-crystalline solar cells. It takes a total of 36 of these type solar cells wired in series to make a panel. Each cell produces about 1/2 Volt. 36 in series would give about 18 volts which would be good for charging 12 volt batteries. (Yes, you really need that high a Voltage to effectively charge 12 Volt batteries) This type of solar cell is as thin as paper and as brittle and fragile as glass. They are very easily damaged. The Ebay seller of these solar cells dips stacks of 18 in wax to stabilize them and make it easier to ship them without damaging them. The wax is quite a pain to remove though. If you can, find cells for sale that aren't dipped in wax. Keep in mind though that they may suffer some more damage in shipping. Notice that these cells have metal tabs on them. You want cells with tabs on them. You are already going to have to do a lot of soldering to build a panel from tabbed solar cells. If you buy cells without tabs, it will at least double the amount of soldering you have to do. So pay extra for tabbed cells.
I also bought a couple of lots of cells that weren't dipped in wax from another Ebay seller. These cells came packed in a plastic box. They rattled around in the box and got a little chipped up on the edges and corners. Minor chips don't really matter too much. They won't reduce the cell's output enough to worry about. These are all blemished and factory seconds anyway. The main reason solar cells get rejected is for chips. So what's another chip or two? All together I bought enough cells to make 2 panels. I knew I'd probably break or otherwise ruin at least a few during construction, so I bought extras.
I also bought a couple of lots of cells that weren't dipped in wax from another Ebay seller. These cells came packed in a plastic box. They rattled around in the box and got a little chipped up on the edges and corners. Minor chips don't really matter too much. They won't reduce the cell's output enough to worry about. These are all blemished and factory seconds anyway. The main reason solar cells get rejected is for chips. So what's another chip or two? All together I bought enough cells to make 2 panels. I knew I'd probably break or otherwise ruin at least a few during construction, so I bought extras.
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I just wanted to say, I built 20 solar panels because of this instructable, so thank you. It helped me a great deal understand about solar power and saving real cash from buying from the electrical company.
Currently on top of my house, there are over 20 panels I made by hand using local materials here in asia using your specs. I bought solar cells from ebay marked as B grade or A grade, almost exact replicas of the images on this instructable. It took over 2 years to complete them (at least for me).
There are a few caveats I ran into while building the first panel, which I shortly learned then fixed on the 2nd panel. Then more problems happened on the 2nd panel until what I have is my 20th panel.
1) Rain. It rains about 6 months of the year. I used silicon caulk bought from Home Depot., to seal the panels as per your instructions. However, water eventually made it through the wood, regardless how many layers of external paint I applied to each panel and upped the amount of silicon to seal.
To solve the problem now, and in the future, I read somewhere else that people bury there solar cells inside clear epoxy. That did the trick. I no longer had problems with water seeping in. However, it did dramatically increase the cost of making the panels. Resin or Epoxy is not cheap even in big quantities.
2) Plexi-glass didnt cut it. It immediately warped the the shape and size and domed. I replaced the plexi-glass with standard window glass cut to size.
Due to the other 6 months, where it doesnt rain, nothing but pure hot sunlight.
3) Amperage is dropping over time. My panels are giving me an open voltage between 18V and 21V. Under load, the voltage drops to around 13.7. (when everything is all connected) The amperage is dropping on some of the panels
The amperage varied when first built gave around 1.8 amps to 2.4 amps.
Now each panel 2 years later, dropped to 1.1 amps to 1.6 amps.
That's a pretty big drop in total amount of wattage. Its also a huge red flag to anyone building their own panels.
4) Repair. If you ever need to repair the cells, you're going to need to open up the panel. For areas that doesnt have extreme weather, resin/epoxy is probably not necessary. But at first, one of the instructions was to glue
the solar cell to the wooden backing, so that it stays put. I'm sure this instructable, never thought about having to repair the panel itself. But gluing the cell to the wooden backing is an absolute no-no. Not only is it frustrating hard to remove, it is almost impossible ( at least in my own experience )
Anyways, thanks for the instructable. Im not sure if DIY is a good way to go now, now that I learned more about the process and building them. The factory stuff bought from the store is already pre-made for outdoor environments. The savings between a panel and building your own these
days is negigible.
this video goes into great detail
this video goes in depth with the whole process
Plastic of any kind will fade in time.
You will also need to pot the solar cells in a special silicone that
is way more translucent then regular silicone.
Otherwise the light is really not getting in.
If your solar panel gets way hot, you will need to spray the underside
to get the wattage back up...heat kills the efficiency of the cells.
The cost to self-make a 100 watt panel is not that much different than buying a panel if you build it correctly. You also have the possibility of running into bad cells, user error and poor materials.
I would only go the DYI route if you’re building a huge system like 1000 watts. You could save 50% over factory panels building a lot of them, then again you may get poor panels. Check Ebay and Amazon for new panels. And remember, don’t buy small panels <50 watts, the cost per watt goes way up due to labor and other materials which are involved in making a panel of any size.
The author claims it produces 18.88 volts OPEN CIRCUIT with NO LOAD. No problem there. This is pretty much typical for 36 cells in series.
The author claims it produces 3.05 amp SHORT CIRCUIT CURRENT. Again, no problem as this is typical of this size solar cell.
And it's true that volts x amps = watts.
However, you can not multiply 3.05 amps short circuit current by 18.88 open circuit volts and come up with ~60 watts (57.584 watts to be exact).
Why?
When the solar panel is short circuited you get 3.05 amps at ZERO volts. 3.05 x 0 = ZERO WATTS.
When the solar panel is open circuit you get 18.88 volts at ZERO amps. 18.88 volts x 0 amps = ZERO WATTS.
What you need to look at is the IV curve (I=current in amps and V=voltage in volts) for the solar cell being used. When the solar panel is producing the maximum amount of power that it can produce the voltage will ALWAYS be LESS than the open circuit voltage and the current will ALWAYS be LESS than the short circuit current. Do NOT expect to see anywhere near the 60 watts claimed for this solar panel if you decide to build it. Depending on the exact solar cells that you get, expect to see more like 30 to 40 watts under load and you will not be disappointed.
This author makes the same error in his "How I built a folding 15 Watt Solar Panel" instructable where he also multiplies SHORT CIRCUIT CURRENT by OPEN CIRCUIT voltage and comes up with 15 watts for 40 cells (or 2.67 watts per cell) which is impossible considering that those cells are only capable of producing ~0.25 watt per cell under IDEAL conditions and more like 0.15 watts per cell under typical conditions.
Again, NICE PROJECT but the author REALLY needs to correct the mis-information he is posting in these instructables and on his website.
Good 'ible and all the comments/discussion has been helpful, too.