DIY Solar Panel

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Member of Weather Underground

I have always been intrigued with solar and while living in Arizona, my friend, an electrician installed solar units on his parents house and then his rental home. It gave me an opportunity to ask some questions. Then while living in Hawai'i, I became friends with a couple of people that were living off the grid. While living in Hawai'i, the desire to get involved with solar was really growing, though it wasn't the right time. No, I waited until I moved back to Michigan, ya you have got that right. The area that probable gets the least amount of sun.

So, this is going to be about the things to keep in mind when thinking about going solar, some you may not be aware and other things you want to know if you do go solar.

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I went to school for electronics so I was familiar with the math equations that are necessary to understand what I was working with. I will pass that along to you and explain how it works, a little bit later. For now let's start at the beginning. I know you probable want to jump to the end to get the answer you're looking for. That's me. In all fairness I will take you through the ups and downs that I went through, by the end you will have a pretty good understanding. I will also include all the links to what I came up with so you can access the same information.

On the left, these are the solar cells that I choose to work with. They are from Everbrightsolar.net . There is a lot of money to be made in this industry which means you could accidentally end up paying a higher price for something that was yesterday news. There are some big bargains out there if you start looking. Let's look at those bargains, many times you will find huge bargains on "Mono Crystalline" solar cells verses "Poly Crystalline" solar cells. What does it mean? First of all, stay away from "Mono Crystalline," if you are serious about what your doing. Here's the difference, "Mono Crystalline" is one layer of conductive material where as "Poly Crystalline" has several layers of conductive material. You will usually see higher volts, amps and watts with a poly crystalline cells.

Before you get started building your solar panel there are some things you might want to think about first. Why do you want to build a solar panel? What are you planning to use it for? I was surprised to find out that if you want to build your solar panels and then use them on your house, you probable won't be able to. You have to check and see what your local codes require to get permitting most times they require UL and possible CEC certification. Now your back to big bucks for just one panel. If you are planning on installing solar panels on your home, you maybe required to have a licensed electrician overseeing the project. I know, you're only working with 12 volts maybe 24 volts. Here's something else to think about. If your home is currently using line voltage, (AC) you may have to get permitting from your utility company to put solar on your home. Yup, you got that right! How about this, if you plan on selling back the extra electricity that you aren't using, on top of getting permits from the utility company, they may not buy your extra electricity. They may offer you, for example five cents per kilowatt hour meanwhile you pay them thirty one cents per kilowatt hour. It may seem like I'm throwing in the towel on the idea, I'm not. I am pointing out the little surprise I discovered. This is where we the people have to step in and demand changes. Keep in mind if you bought your home and it has line voltage, you installed your panels and now a neighbor is complaining that it's an eye soar, you could have some big problems that run into big bucks. The same applies to wind generators too. The neighbor has a better chance of winning in court.

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Ok, you decided to build a solar panel. Congratulations! Let's start off simple, you decide you are going to do four rows with nine cells in each row. That means your going to require thirty six cells, 4 x 9 = 36. Never just buy what you need for the project maybe get 46 cells instead. Every cell must be tested and every cell will vary in it's readings, by having a few extra, you will be able to replace any bad cells. The other reason why you want to have extra cells, they can brake. I know I said I would be supper careful, it happened. Have you ever soldered a potato chip? That's what it's like soldering these cells. If your soldering iron gets to hot, it can cause the cell to warp.

Let's begin testing the cells. You will need a multimeter. A few words on multimeters, Fluke makes great meters, though with that said it can also cost you a pretty penny too. For just experiencing making a solar panel, buy a meter that is inexpensive though be careful, the one I bought from Everbright was bad right out of the box. It helps if you have two meters, that way if you are getting some weird readings you can check with the other meter. I went with a medium price range Radio Shack meter.

Radio Shack Multimeter - DT33C testing.jpg (92533 bytes)

When you are testing the cells you will want to have the brightest of light, that way you can see the highest reading possible. The picture on the right was done on a sunny day. The majority of my cells were tested under a Halogen lamp, 500 watts. Be careful it gets hot fast! When your testing your cells it can be tricky almost like you need four hands and then one hand blocks the sun. The gray side of the cell is positive ( t ) and the blue side is negative
( - ). To test the cell your positive lead from your meter goes on the back of the cell and the negative goes on the silver line. The silver line is called tabbing wire. On the gray side of your cell, you will see six squares, you will want to have them all connected to do the test right. Now you are probable starting to see what I'm talking about when I mentioned earlier you need four hands. There is an easier way! Buy a small piece of copper. You might have to look around for this, I bought mine at ACE Hardware, of all the places you might think of getting it. The have a small arts and crafts section look there. As you can see in the picture on the right, I have the copper plate laying on the table. Lay your solar cell on top of the copper plate, the positive lead of your meter then can be attached to the copper plate. Make sure that the tabbing wire from the other side doesn't touch the copper plate, you can short out the cell. There is a pretty good video on YouTube that shows you how to solder your cells together, check it out.

Ok, you've tested all your cells now you're going to need to put them in a frame. What to know first before moving forward. If you make your frame out of wood, the wood will become weather damaged over time and need repair. If the solar cells are exposed to air, the air will shorten the life of the cells. If you use plexiglass, over time the plexiglass can yellow or develop a haze, which blocks the sunlight. If you use white plexiglass for the backing of your solar panel and seal it with chalking, eventually the seal will break and air will get in. Solar cells work better when the are keep cool. That's right. So, in the summer when your roof is hundred degrees or more, you will produce less electricity then in the cooler months. The point here is you want the back of the cells to be sealed yet open to the breeze to cool them. I'll get back to that in a little bit. The best material to work with is tempered glass. Tempered glass can better protect your solar panel if a branch or something like that was to hit it. I had a custom frame made for my panel. I went to ASF and had the panel shipped to me. I think it was just under $100.

How big should my frame be? Good question! Solar cells come in all different sizes and shapes so there is a formula to help answer that question. Lets use the size cells that I worked with, they are 3 x 5. Three inches tall and five inches long.

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We are going to figure the width of the frame. Here's the formula step by step... You have 4 cells going across at 5 inches each that's 20 inches. We want a 1/4 inch between the cells including the front of the first cell and again after the last cell. That equal 1.25 inches. Then we want 1 inch for the frame on the left and on the right, that's 2 inches. That equals 23.25 inches.

Now let's do the length. That's going to be a bit different.

length_measurement.jpg (36248 bytes) Here's the formula step by step... You have 9 cells going down the row at 3 inches each that's 27 inches. We want a 1/4 inch between the cells skipping the first one and the last one, so that's 8 x .25 which equals 2 inches. Now we want to add 1inch for the bus wire and add 2 inches for the bus wire and junction box ( j-box). Now add the 1inch for the frame at the top and bottom that equals 2 inches. That equals 34 inches.

A little side note here the bus wire is thicker and wider tabbing wire for a simple explanation. You use the buss wire to connect your rows together. So your panel would be 23.25 inches wide and 34 inches long. Once you have your measurements you can make adjustments to the length as you desire.

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As you can see I made adjustments to my math. A few things to keep in mind here, you may notice in this picture some of the gray backing is missing on a few cells... No problem. At this point and time you really want to keep the tabbing wire off the frame. If light gets on the blue side of the cells they will conduct electricity and possibly short out cells.

When you are arranging your rows, you will want to set them up so they either run in series or in parallel. I will explain that when I get into some of the math. After you have the rows arranged the way you want then the bus wire is soldered to the tabbing wire ends. What I have found to be helpful is to use some silicon in various places to hold the cells in place. Once the silicon has dried and the cells are in place, now would be a good time to test the solar panel. The worst thing to find out after you've sealed the panel would be to discover you have a bad solder joint but you can't do anything about it, because it's to late.

Sealing the back of your solar panel. Ok, you checked your panel and you soldered the wires that will become the positive and negative lead onto the bus wire. As I mentioned earlier, aim to keep the solar panel as cool as you can when it is in use. You can put a back panel on or you can use a product called Sylgard 184 . I used Sylgard and it will dry as a clear silicone. Good stuff, a little pricey. The only thing I didn't like about Sylgard was the drying time. I can take several weeks for it to dry and even more time depending on humidity and temperature. Another note on Sylgar, make sure you run about a 1/2 inch bead of silicon about 1/4 of inch out from the edge of the solar cells. You are creating a well to keep the Sylgar from running into the corners of the frame. A mistake I made and a mess I had to deal with. Remember once you pour it on your panel there's no turning back now. There are two good videos on working with Sylgar on YouTube, Video 1, Video 2. Notice in Video 2, how he has a silicon bead going around the outer part of the solar cells. The last two things to install is the j-box and an appropriate sized diode. The j-box can be siliconed on top of the dry Sylgar. The diode gets soldered to the positive lead with the silver line side attaching to your positive lead coming from the solar panel. The diode keeps electricity from flowing back into your solar panel, which would burn-out the cells in time. Remember, most importantly run your solar panel into a charge controller never directly to a battery or device. I picked-up a simple charge controller for about $15.00.

Let's take a look at some terms and formulas that you will need to understand to do this correctly. When you look at solar cell ratings you may see W, V and A. W is watts, V is for Volts and A is for Amps. Sometimes you will see Imax, no this isn't a movie theater. The "I" is also used to express current or amps when you see Imax, you are being shown the maximum amps. Here is a good video on YouTube, check it out. In electronics there is what is called Ohm's Law. It is a way of figuring out Volts, Amp, Resistance, Watts and more then what is needed here.

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Picture from http://www.electronics-tutorials.ws/dccircuits/dcp_2.html

In the far corners you see V, for volts, R is for resistance measured in Ohms and so on. So if you want to work with Wattage issues, "P" you would go to the green quadrant for your formulas. This site has very good explanations about electronics.

Let's try this: Your solar panel is 12 volts, V and your Amps is 3.5A. What is the Watts or Power?

To find Watts we take 12V x 3.5A = 42W
To find Amps we take 42W ÷ 12V = 3.5A
To find Volts we take 42W ÷ 3.5A = 12V

So in the above picture, "I" being Amps... I x V = P, P ÷ I = V, P ÷ V = I. For now there is no reason to deal with resistance. Now the next thing that is very important to understand is circuits. There are three different types of circuits, though when you're building a solar panel you will only use two. They are series and parallel. In series you are just connecting negative to positive. In parallel you join the positive together and then all the negatives are joined and you end up with one positive and one negative. In electronics the effects of a series circuit is very different then a parallel circuit.

Here's what happens: When you connect your rows of solar cells in series, the voltage goes up though the current, Amps stay the same.

So let's say for example you connect in series two solar cells. Each solar cell rating is 1V, 2A. Your end result will be 2V, 2A. See how the amps stayed the same.

Now working with the same solar cells though connected in parallel. Each solar cell rating is 1V, 2A. Your end result will be 1V, 4A. Now the volts stayed the same.

So what's better? They both work great and can be used in combination to achieve your desired result.

Keeping things simple let's create a 12V, 2A solar panel. We have 12 solar cells, each solar cell is 2V, 1A. The first thing is to create 2 rows of 6 cells, they are wired with tabbing wire in series. We now have 2 rows of 12V, 1A. Now we connect the rows in parallel. All the positive tabbing strips are connected with bus wire and all the negative tabbing strips are connected together with bus wire. What you end up with is a 12V, 2A solar panel. What's the Watts? You should get an answer in the twenties.

I realized that I simplified some of the information and examples. This information should only be one of many resources that you have looked into. Good luck with your solar system. I am currently running my Hydroponic system pumps off my solar panel.

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Checking out the system - Back to the top

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