My DIY solar panels

[Dave Turpin]

As promised, here is the write-up for the solar panels I am making.

These are going to look as professional as I can get them. They are 30 volt, 240W panels. They are a lot thinner than most professional machine-made panels that I have seen. The performance is good. Both panels I have made so far made 20v just from the fluorescent lights in the garage. I figure with some sunlight on them they should make the advertised 30 volts.

Design:
6"x6" polycrystalline PV cells, 60 per panel, in 6 columns of 10.

Material list:
Plywood, external, 5/16", 37"x64". $11.67 each at Home Depot.
Glass, 1/8", annealed, 37"x64". $50.00 each from a local glass shop.
Inside corner moulding, 3/4", about 18 feet worth, at $0.45 a foot from Home Depot. (The cheapest plastic crap you can find, because it is not structural, and you can join pieces of it together with a soldering iron)
PV cells, 6"x6", from eBay, pre-tabbed. I got 250 of them for $410 shipped, with about 10 broken in shipping. ($1.70 each)
Epoxy, UV stable, non-blushing. 1.5 gallons for $80 from a local shop. Use about 1/3 gallon per panel.
Construction adhesive. 1 tube, 24 ounces. $3.50 from Home Depot.

Total cost per panel: $191.27. That's $0.80 per watt.


Construction:

My prototype was not the prettiest panel. But it works. Took a couple days of swearing and bleeding until I figured out the best way to tackle the construction. I basically did everything backwards the first time. So these pictures are from my second panel, which took 5 total hours to make.

Step one:
http://i207.photobucket.com/albums/bb21/bpestilence/IMG_0609.jpg

Lay some spare plywood or cardboard flat on the ground. Then carefully lay down the glass, and lay a sheet of plywood over that. Center it up as best you can. The cuts that I got from Home Depot were about 1/4" off, so I centered it will a little glass visible from each edge. The moulding takes care of this discrepancy.

Step two:
http://i207.photobucket.com/albums/bb21/bpestilence/IMG_0610.jpg
http://i207.photobucket.com/albums/bb21/bpestilence/IMG_0611.jpg
http://i207.photobucket.com/albums/bb21/bpestilence/IMG_0612.jpg

Don't go crazy measuring the moulding with too much detail. Butt the moulding flat against the glass and plywood, and screw it together with 1/2" screws. I had the screws laying around. Mark the corners and cut at 45 degree angles, so that the line of the angle intercepts the corner of the glass or plywood, whichever is bigger.

http://i207.photobucket.com/albums/bb21/bpestilence/IMG_0613.jpg

Here is the benefit of the cheap plastic moulding. No waste. If one piece is not long enough to make an entire edge, ust cut another piece to fit and melt them together with a soldering iron. Remember, these are not structural, they just hold the glass in place.

Step 3:
http://i207.photobucket.com/albums/bb21/bpestilence/IMG_0614.jpg

Before putting on the last piece on the bottom edge, cut some 6" lengths of bus wire and fold them around the plywood. Put them about 3" in from the outside edge. These will be the positive and negative leads.

Step 4:
http://i207.photobucket.com/albums/bb21/bpestilence/IMG_0615.jpg

Now that this is done, pick up the plywood. Carefully move the glass aside (stand it up to prevent damage) and then place the plywood back down with the open edge of the moulding upward.

Step 5:
http://i207.photobucket.com/albums/bb21/bpestilence/IMG_0616.jpg
http://i207.photobucket.com/albums/bb21/bpestilence/IMG_0617.jpg
http://i207.photobucket.com/albums/bb21/bpestilence/IMG_0618.jpg

[Dave Turpin]

http://i207.photobucket.com/albums/bb21/bpestilence/IMG_0619.jpg
http://i207.photobucket.com/albums/bb21/bpestilence/IMG_0620.jpg


Now we start working with cells. These cells were delivered sandwiched between layers of cardboard. Take the first piece of board off. If you are looking at the blue side, put the cardboard back on and flip the stack over. Once you are looking at the bottom (the positive side) decide on what polarity you want. I did negative on the first, lower right cell. When flipped and turned on end, the right side will remain the negative side. So make sure the tabs extending from the TOP of the cell faces downwards. If you have untabbed cells you choose which way to go on this, and this would be the step when you would attach the positive leads on the underside of the cells. It doesn't matter which polarity you choose, so long as you alternate polarity between columns to keep the panel in series arrangement.

Put a dab of construction adhesive on the grey side. As in the pictures, gingerly flip the cell using the cardboard to handle and arrange the cell. But the edge of the cell against (or very nearly against) the moulding. With a width of 37", there is room for 6 cells wide (they are 6.15" each) with about 0.05" to spare. There is plenty of room on the length, so that you have room for bus wires.

Shimmy the cell around, spreading the glue, using the cardboard to touch the blue side. Remember: These things are wafer thin and as fragile as butterfly's wings. Once you are happy with the location of the first cell, leaving room for the bus wire, move on to the next cell.

http://i207.photobucket.com/albums/bb21/bpestilence/IMG_0621.jpg

The next cell should be prepared and placed the same as the last cell. If you are going up the column, leave this much room between the cells to allow for soldering. If you are going over to the next row, butt one cell up against the next one, and make sure the polarity of the cell is flipped. When you connect the bus wire, one end must connect to the positive tabs of one row and the negative of the next. The cell up-column it the same, but each cell is arranged the same. So if you are doing the second cell in the first column, the negative tab should be adjacent to the positive tab of the first cell. Solder as you go. After a few rows are done, you will want to turn the whole panel around (if you didn't start at the top to begin with) so that you can finish the rest of the cells without having to precariously perch over the fragile cells.

http://i207.photobucket.com/albums/bb21/bpestilence/IMG_0622.jpg

My cells were pretabbed, but there were still some tabs that did not extend beyond the edge. Just solder a small length of tab wire to extend them. About 3mm over the edge is all we need to connect to the next cell, longer tabs at the ends with the bus wire.

http://i207.photobucket.com/albums/bb21/bpestilence/IMG_0623.jpg
http://i207.photobucket.com/albums/bb21/bpestilence/IMG_0624.jpg
http://i207.photobucket.com/albums/bb21/bpestilence/IMG_0625.jpg
http://i207.photobucket.com/albums/bb21/bpestilence/IMG_0626.jpg
http://i207.photobucket.com/albums/bb21/bpestilence/IMG_0627.jpg
http://i207.photobucket.com/albums/bb21/bpestilence/IMG_0628.jpg

[Dave Turpin]

More pictures of the process....

Step 6:
http://i207.photobucket.com/albums/bb21/bpestilence/IMG_0629.jpg
http://i207.photobucket.com/albums/bb21/bpestilence/IMG_0630.jpg


Now we mix epoxy. I did each panel in two pours. About 1/3 gallon per panel. Even this leaves some air bubbles in the finished product. You might want to splurge and double the epoxy amount, which will be enough to pot all the cells without air bubbles. It doesn't matter, though. The panels make the same voltage with or without this glazing. The epoxy simply ties the plywood to the glass, making it a tough composite. At also protects the cells from cracking. The glass protects them from hailstones and dirt.

http://i207.photobucket.com/albums/bb21/bpestilence/IMG_0631.jpg

Use a spatula or a piece of cardboard to spread around the epoxy. At least make sure every cell is completely wetted. Again, this ensures no piece of a cell can crack off. Besides this, try to spread it evenly so that at least some of the epoxy touches the glass, making a good solid composite layer.

Step 7:
http://i207.photobucket.com/albums/bb21/bpestilence/IMG_0632.jpg

This is where a cluttered garage helps. After the epoxy is spread, clean the glass and then carefully, carefully lay it down over the epoxy. It should fall in place perfectly because it was there previously when you put the moulding on. Now put some more spare plywood on top of the glass, and then stack a couple thousand pounds of crap on top. This is almost as good as vacuum bagging. (Although vaccum bagging and more expoxy would definately make it look a lot more professional, since there would be no bubbles in the glazing)

24 hours later, the epoxy is set up and the cell is ready! Take the stuff off, and set it aside. Now wire the leads however you want. I did mine very simple. Since I am using 3 panels in series to make 90volts for a grid-tie inverter, I am not using diodes at all.

Performance data to follow!

[Dave Turpin]

Performance data:

Still to follow. These panels unfortunately met a bad end as the family dog knocked them over and they slammed into the concrete floor. But... I have smaller 100W panels in the works for my sump pump battery backup and I will be able to generate performance data soon.

I am also going to build them with about 2x as thick OSB backing, and more epoxy potting.

[Steven Fahey]

Oh no!

All that work is gone.

Hope you're not frustrated, because the cost savings is very impressive!

Your trick of using wood moulding opens the potential of making your panels "architecturally" integrated to the house. Though I'm not 100% comfortable with you using OSB. It's not as dimensionally stable as you'd probably want it to be, and of course it will swell if it gets wet somehow.

Keep leading the way I still look forward to more!