How to Build a Solar Panel
Solar Panel Construction
Currently, the limiting factor for widespread adoption of solar is the initial cost of the completed solar system. While a typical solar system will consist of many components, the solar panels often comprise more than 50% of the entire cost. This accounts for thousands of dollars even in the smallest of residential cases. Solar panels, when made yourself can be done for a fraction of the cost of what is available commercially and can ultimately save you a lot of money, whether you opt for building a small 65 watt solar system or for wiring several panels together and creating a larger system. Even with no experience and limited access to tools anyone can learn how to build a fully functional PV panel and can begin producing energy from the sun in just a few hours. For the purpose of this DIY panel we will be dealing with crystalline cells and the following is a basic guideline in what steps to take, which methods to employ and which tools to use to build your own metal framed and encapsulated solar cells panel.
Note: If you are not going to encapsulate the cells (an alternative for drier climates with little rain and humidity) people have simply attached the cells to a substrate with a dab of silicone caulk on the back side of the solar cells after the rows of cells have been soldered together and used a wooden frame with a plexiglass cover. While we do not advise this method because moisture will get inside the frame and onto the cells and regular exposure to oxygen will cause the cells to oxidize and loose efficiency, it is a cheaper alternative for beginners or for short term panels.
It is always better to build an aluminum frame and encapsulate the solar cells to the front glass of the panel. Also, when encapsulating your cells, do not use plexiglass as it will expand and contract in the sun and will delaminate from the cells within a few months.
Since the cells will last 25+ years, why not build a frame that will last just as long? The instructions below discuss the preferred way to build your panel, and while it may cost 2 to 3 times as much to build your panel(s) this way, they will last 5 to 20 times as long!
Tools and Materials
As stated before, most of the following tools and materials can be sourced locally. The rest can be found online and through national distributors that ship via USPS, FedEx or UPS.
- Eye Protection
- Metal File
- Rivet Gun and Rivets
- Clear Glass Panel
- Aluminum Angle
- Solder Gun
- Caulk Gun and Silicone II Caulk
- Carpenter’s Square
- Bond paper or construction paper
- Plastic Back sheet
- Solar cells and tabbing wire (contact our partner solar cell distributor Accessolar for these at email@example.com and tell them we sent you!)
- Bus Wire (available from Accessolar)
- Tab Wire (available from Accessolar)
- Encapsulate (available from Accessolar)
- Flux Pen (available from Accessolar)
Step #1 Determine the Frame Size
First, take the dimensions of your individual solar cells, in our case 3.25” x 6”. There are two main panels layouts that you may wish to work with. The first and the one we will outline are 4 rows of 9 cells wired together. The other option is to use 3 rows of 12 cells, but in any case you will want to use 36 solar cells to charge a 12 volt battery.
Working with the example of the 4 rows of 9 cells, we need to determine the width and length of the panel. If each cell is 3.25” x 6” and there are 4 cells wide we will need at least 24” (6” x 4 = 24”). Typically you will want to allow at least ¼” in between the rows, and an inch on the right and left sides. In total you get should 24 ¾”, but we’ll round this up to 25”. Do the same math to determine the height but allow a little more spacing on the top and bottom of the panel for your bus ribbon connections. That leaves us with 25” x 34.25”. This is the dimension necessary for the inside of the metal frame.
It is important to note that this is the minimum size for your panel. If you find a precut piece of tempered glass or a metal frame that is a little larger than the dimensions given that you can work with it, just add more spaces in between the cells or along the edges. The important part is that you provide enough space within the inner dimensions of the panel frame for all of the cells. Perform the same calculations for a panel comprised of 3 rows of 12 cells but make adjustments as necessary.
Step #2 Build the Frame
For building the metal frame aluminum is the best choice. One, it holds up very well against the weather elements and is very rust resistant. Second, it is lightweight and easy to work with. Plus, all this comes at a very competitive cost. For a 65 watt panel you will need about 10 feet of Aluminum stock angle. We have found that 1″ x 1/20″ aluminum angle provides a strong enough frame with proper bracing, and you can also cut 3/4″ sections of the left over angle to make corner braces. This can be found at any local hardware store and should cost less than $15 for the entire length.
Measure out the aluminum channel to fit outside of the solar cells. Take your measurements from earlier from the inside of the metal frame and then add the depth of the aluminum channel. This will give you your outside dimensions of the panel. Make sure the inside edge of the angle when completed will be able to accommodate all of the your solar cells.
Use a carpenter’s square and measure 45 ° angles. With your hacksaw, make perfect 45 ° angles on each piece of aluminum. Use the metal file to file down any sharp edges and make sure that when two sides line up the angles fit well together.
Measure how large the glass piece for the panel front needs to be and cut accordingly. Lay it in the cut frame pieces to make sure it will fit properly. Once you see it fits in properly, apply caulk on the inside edge of the aluminum angle where it will fit with the glass and lay the glass back down and apply enough pressure to get the glass firmly bonded to the aluminum frame.
The corners will be held together with the 3/4″ pieces you have cut out of the aluminum angle extra length. Line up the braces in each corner and drill a hole through both sides of the aluminum angle brace. Apply Silicone II Caulk to the backs of the corner braces, put them in place so the holes line up and then use your rivet gun to pop rivets into all 8 holes to securely keep the frame in place.
Step #3 Solder the Solar Cells
If you have pre-tabbed cells (the ones with the thin tab ribbon coming off of the face) you will only have to solder the cells together at the back, or negative side. If untabbed, apply solder to the tab ribbon and connect the tab ribbon to the front bus bars that run from the bottom of the cell all the way to the top of the cell on the negative side. You will have to do this twice for each 3” x 6” cell as you will have two bus bar strips. Allow enough tab ribbon lead to come off of the cell to attach it to the back side of the next cell in series, roughly twice the height of your cell.
Once you have 36 cells with tab ribbon coming off the face of the cell you will want to begin soldering the cells together in series. A good trick here is to build a template for the cells so that the solar cells are evenly spaced apart and when you are soldering they will not move very much. A template can be made with tile spacers attached to a piece of plywood. Measure carefully and attach a tile spacer in the spacing between each solar cell if you don’t want to eyeball it.
Lay each cell in place to begin connecting them in series. Each cell will be laying face down with the tab ribbon leads coming off in the same direction. Apply a little bit of flux to all six exposed contact points on the back of each cell with your flux pen. This will help draw the solder onto the cell and will make a stronger solder joint.
Once the cells have been fluxed take your solder gun and apply a little bit of solder to each tab ribbon. This will save you time when connecting the tab ribbon to the back of the next cell. Use a solder pen or similar object to keep the tab ribbons in place and apply a press the ribbon down onto each exposed contact point that you have pre fluxed. Do this along each string of cells until you have connected each string of cells in series.
Once each string is completed, cut a strip of tab ribbon to attach to the back of the first cell in each string. This will ensure that you have tab ribbon leads coming off each string. You will need tab ribbon leads on both ends of the strings to connect each string together with bus ribbon when on the glass.
When all of your strings are wired together go test them in the sun to ensure the series connections were done properly. If there is a problem in one of the strings this is your best chance to isolate it and fix the issue before the cells and all connected on the panel and the encapsulate has been poured.
Connect the strings together using your bus ribbon. Connect them so that the flow of power goes through each solar cell in a series circuit to get the proper voltage.
STEP #7: Pour Encapsulate
Take out the Sylgard 184 Silicone Elastomer Base and its Curing Agent. You will want a clean container to mix the two chemicals together and something to stir it with. A Food Saver jar works especially well since it can be capped with a hand pump attached to it to vacuum the air bubbles out of the mixture.
The 0.5 kg kits are the perfect amount for one panel, although with some practice you can get by with using only 90-95% of the kit per panel. Take the entire contents of the Curing Agent and slowly pour it into the container with the Elastomer Base. It is very important that you completely mix the two together so that the curing process is even throughout the panel.
Once the encapsulate has been mixed you will have at least an hour before the solution starts to harden. Colder climates will make it where the encapsulate has more time to cure. You can take your time and do it correctly here. The bubbles that emerge in the mixture will eventually be transferred to the panel and become bubbles on the face of the glass if they are not removed. By vacuum sealing the jar with the mixed encapsulate inside you pull the air out of the container and the air bubbles will naturally draw out of the mixture. The container should ideally be vacuumed 29 Mercury (Hg) of pressure, if possible, to remove all of the air bubbles from the mixture. If you cannot achieve 29 Hg of pressure in the container and some bubbles remain you will have the opportunity to mitigate the bubble factor later on.
Lay the panel out with the front face down and place the cells on the glass. You will want to ensure that all of the soldering is done before you pour any encapsulate. Make sure the panel is completely flat. pour the encapsulate over the cells slowly and evenly. Don’t create air bubbles by pouring on all 4 sides of the cell. The encapsulate will flatten out and fill the space between the front of the cell and the glass.
Next, place the bond paper on the encapsulate. This bond paper will absorb some of the encapsulate and become attached to the cells. This provides some strength to the encapsulation of the cells, as the fibers in the bond paper harden in the mixture to add rigidity. Place a weight over the back of the panel so that the cells are lightly pressed against the glass nice and flat. Carpet matting or newspaper under a piece of plywood cut to size would work.
You will want enough pressure to flatten the cells, but not too much to break the cells. This is where good, flat solder joints will help out. If your soldering on the faces of the cells was sloppy it could make the cells harder to lay flat on the glass and cause more air bubbles to form. Once all of the encapsulate has been poured and the bond paper has been placed on top, let sit for a few hours before checking back on it.
STEP #9: Lay Back Sheet & Wire Junction Box
At this point you are almost done. All you need to do now is lay the plastic back sheet to further protect the cells from the elements and wire the two bus ribbon leads into a junction box. Cut holes in the plastic back sheet and pull the bus ribbon leads through the plastic. Using an adhesive like spray adhesive or silicone caulk, secure the back sheet to the encapsulated cells and attach the junction box to the back of the panel with glue. Make sure that the wires coming out of the junction box have strain reliefs of some sort so that if the wires are pulled on they will not pull the bus ribbon from the front of the panel.
Go and test in the sun and install. Congrats!
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