On Saturday, itek Energy, the producer of the solar panels used in our system, held public tours of their factory, right here in Bellingham. We got to tour with a small group of folks at 10:30am — we learned a lot and took some photos. Here’s what we got out of it:
itek receives the solar cells from another North American company, where they are sliced to a thickness of about 200 microns from a cylinder of silicon. The reason the cells have all their corners cut off on them is because that’s the diameter of the cylinder they are sliced from.
itek uses one of two machines to line up the cells in rows of 10, with wires soldered between them. The cells being very thin makes them quite fragile, so they occasionally crack during this process. One machine is older and makes mistakes on about 5% of the strings. Their newer machine only makes mistakes about 1% of the time, and is also much faster. All of the strings of cells are inspected by a trained person. If a broken cell is found, it is saved to be recycled.
Next they assemble six strings of cells face down on to the glass. The tempered glass has a rough texture (referred to as “prismatic”) on the inside to cause the light to bounce around inside and reach the cells, instead of reflecting back out. It looked kind of like the surface of a fly’s eye. Between the cells and the glass they place a sheet of a substance that felt and looked a lot like waxed paper. It melts down later in the process, becomes transparent and holds things together.
After being carefully positioned on the glass by the machine, then adjusted and inspected by a worker, the cells are taped down with Scotch Magic Tape to keep them from shifting through the rest of the process. The wires at the ends of the lines are soldered together by hand to create two series of 30 cells each on each panel. itek attributes this hand-soldering to their very low failure rate. They have never had a panel come back because of a failed solder joint. In fact, they’ve only ever had 3 panels fail, of the tens of thousands they have made (I think they said 70,000), and all of them were easily fixable.
After soldering, another layer of the melting sheet is placed over the cells, and then a specially designed backing sheet, which is white. This is what is visible on the back side of panels.
Four panels at a time then enter a laminating machine. This machine heats up the panels to cause the glue sheets to melt, then it presses all the layers together. Once they cool, the layers are permanently stuck together.
After another inspection to check for any possible foreign debris or cracked cells, the panels are then ready for framing. They have developed their own method for attaching the frames by hand. They have a machine that can do it, but it’s actually faster for them to do it using their workers, so they continue to do it that way. At this stage the electrical box is also attached to the back of the panel. itek puts diodes in the box on the panel to allow for one string of cells to produce a different amount of power than the other string, in case of shading issues.
Once the panel is assembled, they then test it. The mechanism for testing is called a flash table. The panel is placed face-down on this table and the leads are attached to a computer. On command, the table flashes a very bright light up at the panel. The computer records the electrical profile of the panel during this flash. They can determine, from that, what the capacity of the panel is, and if there’s anything wrong with it.
After that, the panels are stacked up and ready to deliver to customers!
I was rather impressed by the process. They clearly put a lot of thought into it and seem to be finding ways to improve their process and their panels all the time. It was great to hear about all the details and see how hands-on everything is. It’s also great to have a local company doing this, employing local people. Being a small, local company, and due to their hands-on process, they are also able to often accommodate special needs if someone is looking for a different sized panel, for example.
By the way, they have an array of 64 of their own panels on their roof! It’s not enough to cover all of their power needs for manufacturing, but nevertheless solar panels made with solar power is really cool.