MACH II is Complete
I wrapped up the “MACH II” today. Everything was looking good until I dropped it while framing it and put a crack in the corner of the glass 
. However, the cells are still in tact and it is still working. It’s ok, the MACH II was only another prototype anyway. I will apply the lessons learned to the MACH III.
Here is what needs improvement as of now:
1. I need to rebuilt the jig for soldering together the cells. There was too much wiggle room in the last one and the cells weren’t perfectly aligned. This causes the cells to not lay down completely flat against the glass because the wire between the cells sometimes buckles a wee bit when things don’t line up perfectly. It also looks a little shabby.
2. I used a heat gun to bake the EVA around the cells. This approach is -=not=- a good one. There was lots of bubbling and blistering, and the heated EVA is plastic, sticky, and not something one can work with during the process. A vacuum table is the way to go, so if I want to work with EVA in the future, I have to find a way to DIY a vacuum table.
3. I’ll probably scale up the MACH III so that it is as large as a commercial panel.
Here are two pictures. The first is prior to baking the EVA, and the second shows the finished product.
Throwing the “Mach 1″ in the Garbage
If you recall from an earlier post, I strongly advise against using wood in the construction of your panels. Many “DIY” panel instructions use crap around the house as the platform for the cells. These panels are going to sit in the elements and you want them to last. Wood requires a lot of maintenance. It is not what you want to do.
Below is a picture of my “Mach 1″ solar panel. I built it following some instructions I found on the Internet. Two years later it is warped, moisture has gotten in, and it no longer works. Yes, I could have done a better job and it may have lasted longer. But how many things made of wood can be left outside for 25 years? I’m using metal, glass, and professional encapsulation from now on.
Measuring voltage before soldering rows together
Now that I have soldered together four rows of cells, I wanted to measure each of the rows before soldering them together. It makes sense to make measurements every step of the way to minimize the amount of rework required if I had a bad component. I expect each row to be about 4.5VDC because the rows are comprised of 9 cells, each rated at .5 volts. 9X.5=4.5. My rows were about 4.9VDC, as shown in the image below.
I simply laid the rows out in the sun. The professionals have calibrated light sources, sort of like a suntanning table, that they use. I doubt I’ll ever get to that level of maturity, but who knows?
The picture shows the output of one row of cells. Each row measured the same. So I’m good to solder them together now.
Frame Material
Although my current prototype uses commonly-available aluminum angle, the retail units use an extruded aluminum frame that look like the images below. I am currently trying to find an affordable source of these frames.
Cell Spacing on the Panel – 2mm between cells.
One thing I notice on many of the DIY designs is the amount of wasted space on the panel.
The professional panels do what they can to make the panels as light and efficient as possible. To that end, they put the cells very close together but not touching. They leave 2mm between cells, or about the width of the tab wire running through the cell. This probably leaves a little room for heat expansion. It is also aesthetically pleasing.
Side Note: The Biggest Consumers of Energy in the Home
This article from the U.S. Department of Energy lists the appliances that usually consume the most amount of energy in the home:
http://www1.eere.energy.gov/consumer/tips/appliances.html
I’m not going to go deranged green here, but I have seen some very practical approaches for reducing the amount of energy consumed by some of these appliances. For example, here is a creative way to direct hot air from your attic into the dryer, which in summer reduces the amount of energy required to heat the air and also vents the attic, a win/win situation. It makes sense, and apparently is already more-or-less standard in countries outside of the US.
Awhile ago I walked around the house with a Kill-a-Watt and closely studied the behavior of every energy-consuming thing in my house. As a result, I was able to make some changes that really reduced my electricity bill. That said, I can really drive myself crazy with that stuff, so it is good to get a little perspective. A flat-screen TV, for example, costs about $70 a year on average.
The key issue is practicality. Is it really worth spending $1000 more on an appliance to save several dollars a year? And if I plan to sell my house eventually, who is going to want to buy it with all sorts of one-off modifications to it? So I try to keep myself constrained to home modifications that are palatable by the mainstream or can be easily undone. And I try to limit my purchases to things that -=mostly=- will pay for themselves in a reasonable amount of time or that are simply so appealing to me that I feel good about making the change. It can’t all be about money, but it is -=primarily=- about money for me.
One last note: We replaced the “can light” bulbs in our living room with CFLs. There were 10 50Watt bulbs in there. That is 500W whenever they were on, which was all the time no matter how much bitching I did to my family to turn off the lights. Replacing these bulbs with 5W CFLs reduced the wattage to 50W. The bulbs were a few bucks each and I bought them from 1000bulbs.com (I recommend them, as my experience with them has always been positive). The energy savings were immediate and the bulbs paid for themselves in just a few months.
The Panel is Here
Its a Canadian Solar 200W panel. At first blush, I have a couple of observations:
1. Its a lot bigger than the kind you see DIYers building on the Internet. It uses 6″x6″ cells in a 6×10 array.
2. It is heavier than I expected.
I have attached a photo. Keep in mind that my goal is not to rip off anyone’s design, but rather to ensure that the panels I build will work with off-the-shelf panels. It also gives me a benchmark when measuring power output of my panels.
So what to do with the boxes of 3″x6″ cells that I bought? Well, it occurs to me that there is nothing wrong with having panels of different sizes. I have places where the smaller ones that I’m building will fit, and of course the large panels are good for my roof. But consistency is important. All the panels of different sizes should have the same dimensions, mounting holes, etc., so that they can be clustered together.
I Broke Down and Bought a Panel
I decided to buy a 200w panel from ebay for $606 (including shipping). I want something to compare my panels to, in particular to ensure that my panels have standard sizes, mounting holes, etc., to integrate with standard installations. I could get those off a spec sheet, but I also wanted a professional panel that I could use to compare power output with the output from my panels.
The panel I ordered is a 60 cell panel, which is a common size. I am going to graduate to 60-72 cell panels after I finish this prototype. I also believe that moving to a larger panel is ultimately going to reduce the cost per watt of the panels I make.
My intent for blogging my experience is to allow other DIYers to learn from my mistakes and hopefully avoid some of the costs from those mistakes. I’d rather not spend this much money on a panel, but I think it will ensure that my panels are better and that anyone reading this blog will not have to cover the same ground.
Soldering My First Row of Cells
I’m not going to spend any time talking about soldering techniques or how to solder together cells. There is actually lots of really good information out there. YouTube is probably the best place to look, because people actually record themselves doing it.
All you need to know is that I’m presently building a 36 cell array, 4 rows with 9 cells per row. I made a template using 3″x6″ subway tiles from Home Depot, glued to a 1″x8″ board. The template also has a straightedge on one side and some metal dowel pins to hold the cells in a fixed position while I solder them. I use the template only for cosmetic reasons. The finished product will look professional and ensure a tight fit (2mm apart) of the cells for an efficient use of surface area. I use the tile because the cells are thin and the soldering iron is hot. When I soldered my first row of cells together, the cells fused a little to the table I was working on and also burned the table; the tiles prevent that.
I find that having the cells held in place helps me reduce breakage and that my soldering job is better. Both of these things are CRITICAL to creating a quality product. Here are some pictures of the template:
