Handmade solar panels: if I can make them, anyone can!

I’ve been planning the handmade solar for a while, and this February I finally pencilled off what I thought was enough time to get it done.

The week started on Sunday when I drove to Manchester, where I’d arranged to get the bulk of the work done, and realised I’d left my multimeter at home. On Monday, I found that the power lead of my soldering station wouldn’t reach the plug. On Tuesday, it came to my notice that I did not have a board to  use as a top layer whilst curing the silicone. By Friday, one of the panels wasn’t working at all. During Saturday, I trawled unsuccessfully around the area for a non-return diode. By the time Sunday came around again, though, I was nearly done. I spent all afternoon up on the roof and, despite the super sticky stuff I’d bought the day before turning out to be set solidly inside its tube, I managed to affix the panels to their backing board, surround them with a (reasonably) effective frame, seal the edges and achieve more than 3 amps output. Which made me happy. And tired.

 

Handmade Solar: The Opening Stages

 

These are 6″x6″ B grade solar cells, bought on Ebay. The seller is mini_vini_vinci. It’s worth doing some comparison regarding prices, as they vary hugely. Perhaps even a spreadsheet, if that’s how you roll. Mine was done on a bit of paper. I would show it to you, but it seems to have gone missing. Instead, here is my original plan:

…in which  I work out how many cells I can fit onto my glass, and plan how they will be linked together. I had an old double glazed unit, therefore two pieces of glass, so I decided to keep the cells whole (ie. 6″x6″, rather than cutting them into more manageable 6″x3″ rectangles), and have 18 cells on each piece of glass. The panels would then be linked together to make one big 18V panel.

The numbers are arrived at by working out how much power you need from each panel. I wanted to charge 12V batteries, so I needed my panel to produce 18V in total. Each cell (whatever its size) produces 0.5V, therefore I need 36 cells linked together in total.

In retrospect, I wonder if I would have been better cutting the cells in half, and having two smaller panels, each with 36 half cells. This would still have produced 18V. My understanding was that larger cells produce more amperage (current), so a larger panel was worth going for. My next panel will be with 3″x6″ cells, so I can compare.

Taking the double glazing unit apart was tricky, and I ended up breaking the glass. I had a deadline (for an article in Permaculture Magazine), so I carried on with the glass that I had, hoping that the silicone layer at the end would seal up all the gaps. It didn’t, really. Another lesson learned.

 ♦

What follows is an overview of the handmade solar process, with examples of things I did wrong, wish I’d done better, or will do differently next time. It’s not intended as a standalone tutorial. I’m really not an expert. Though, honestly, if I can do it, you can do it.

 

Putting it all together

 

 Step One

Multimeters are great, but also confusing, so it’s handy to have someone around to show you how to use one if you’re not familiar with them. Check everything as you go along. Check that each cell is producing power before you solder. As I said, each cell should give out 0.5V, but this will be less if you are measuring the voltage inside, or on a cloudy day.

 

 Step Two

For handmade solar, you’ll need a soldering iron of at least 60W, which will reach a temperature of 450°C. I was very happy with the soldering station that I bought from http://www.circuitspecialists.eu. Buy extra cells to practice on. Keep the tip of the soldering iron clean.

Cut tabbing ribbon to length, each piece 3/4 as long again as the white line on the cell. Apply flux. Solder down the ribbon with one slow run of the soldering iron, making sure you start the ribbon off a couple of mm below the top edge.

 

 Step Three

String the cells together by turning them over and soldering the ‘tail’ of ribbon onto the back of the next cell, following the same line. Two things to remember here. First, the ribbon needs to follow a regular over/under pattern. Second, keep the strings as short as possible. For my panel, each half had 18 cells, so I made them into six strings of three rather than three strings of six.

When you have your strings, test them again with your multimeter. The reading should go up.

Step Four

 

Lay out your backing board on polythene, and cover it with kitchen roll. Arrange the strings of cells so that the ribbon continues its over/under pattern. Starting at the top left cell, the ribbon will go over/under to the bottom of the string, and then will start at the bottom of the next string going over/under up to the top. Then over/under down, over/under up and so on. Check this, then check again. And, while you’re checking, make sure that there is a gap between the edge of the cell and the beginning of the ribbon. On every one.

Join the ends of the ribbon together with a cross piece and a small blob of solder. Remember that the ribbon is a continuous link, so it should end up going top-to-bottom, across, bottom-to-top, across, and so on. Put something under as you solder, so that you don’t set your kitchen roll alight.

Check with your multimeter, using the beginning and end tail of ribbon. The reading should be higher again.

 

Step Five

You will have a ribbon end at the start and finish of the panel. Make a hole through your backing material at these points, and tuck the spare ribbon ends through. These will be where you wire up your panel. Remember that the cells are fragile, so don’t do as I did the first time, and bend the backing material when you poke the ribbon through. It will snap the cell. I found it best to hold the ribbon down with my thumb just where it left the edge of the cell, then bend just the ribbon.

 

 Step Six

Mix the two parts of the silicone together in a jug. Do this slowly. Mix them by rotating the jug itself in a circular movement. Do this slowly. Don’t be tempted to mix with a spoon or likewise. You want, above all things, to avoid bubbles.

A good question here is, how much silicone? I bought mine from KnowYourPlanet.com, and went for the 220g size. The total surface area of my panels was 1m², and this was just about enough. I wish I’d had a little bit more.

When it’s good and mixed, pour it (slowly!) over your cell arrangement, following a line up and down all of the strings, then round the edge, then across the gaps. Use a piece of card to smooth it over the whole area..

Let the panel sit for ten minutes or so, to allow any air bubbles to rise. You can prick these with the point of a knife, a satisfying and thankfully skill-free interlude.

When I make my next lot of panels, I’ll remember to take photos of this stage…

 

Step Seven

Lay your glass down on top of the panel. Press it firmly from the centre to encourage any remaining air bubbles to move out to the edges. Cover with polythene, and place a board over the top. Then add weight on top of the board. Leave for up to three days for the silicone to set. In a warm room, this could take as little as 12 hours.

 

 The End Game

… to be continued in another post, including wiring issues, and how the panel has worked… Watch this space! And please feel free to contact me with any questions, suggestions or things you’ve noticed that need to be explained.

 

In the meantime, do visit Handmade Solar on Facebook. Norman was the guy I learned all this from. If you want to start your handmade solar career by going on a course like I did, click here to find out about LILI, the Low Impact Living Initiative.