solar Cells, how do they work

OK, I spent days learning about solar cells, to get to the point where they actually made some sense, mostly because I didn't get a basic concept. The cells themselves are all about surface area, and they are about as simple in construction as it is possible to be. The entire front of the cell is the 'positive side' and the entire back of the cell is the 'negative side'. So if I take a solar cell out of its package, drag it into the sunlight, and touch the positive probe from my multimeter to anywhere on the front, and my negative probe to anywhere on the back, I can get the voltage of that cell. The cells that I ordered have 2 parallel stripes down the front, where I can solder the tabbing wire (a special thin, flat wire that will lie flat under the cell), and there are 6 solder points on the back (little squares of pre-applied solder, I believe) 3 on each side line up with the parallel stripe on the front. So if I were to connect 5 cells together, the first cell's positive wire would be connected to nothing (later on, it connects to the positive terminal on whatever we are powering) The negative side will be soldered to the positive on cell 2. The negative side on cell 2 will be soldered to the positive side on cell 3 and so on, until cell 5 where the negative wires will be nothing, to form the negative terminal to whatever we are powering.

So, to design my panels, I had to understand parallel and series wiring. Read below, or visit the wikipedia entry.

The first is wiring in series. If you connect several cells, + to -, then the voltage goes up while the current stays steady. For example, if connect 10 cells together, in series (cell 1 negative terminal connects to cell 2 positive terminal. Cell 2 negative terminal connects to cell 3 positive terminal and so on), and each has a voltage of .5, this means you will get 5 volts (10*.5 volts) out of the cells. I actually tested this out, by taking 6 AA batteries, and lining them up, positive to negative. Each one is rated at 1.2 volts, but in actuality produces 1.4-1.5 volts fully charged (there are electronic rules that tell us that when we place the batteries under 'load' this will drop to 1.2, so this is actually a proper voltage reading). The voltage reading was 7.8, so the 'series' wiring was proven out. This is called wiring in series. Incidentally, this explains why, if you are jump-starting your friend's car, and connect positive to negative, instead of positive to positive, you blow up both your electrical systems. Doing so essentially drops 24 volts through both cars, frying everything in sight.

Second is wiring in parallel. When we do this, the current increases, while voltage stays the same. In this case, we are connecting the leads from positive to positive. in the car battery example, the voltage will end up being 12 volts, while the wattage is the sum of the 2 batteries' wattage.

These 2 concepts are important to understand, because the solar panel has to be of a sufficient voltage and wattage to run the grid tie inverter, which will be explained in a later post.

I'll get through a couple more 'concept' posts, then start posting pictures of what I've done. I'll also post cost information, as well as establish some baseline of what the break-even point is on a photovoltaic system.