Over the past few years I have been learning about solar panels, and power plants in general. My next step towards becoming a solar panel expert was the purchase of a 10-watt multicrystalline silicon solar panel. The short circuit voltage is up to 20 volts.
Its efficiency is 10%, meaning that a square meter of these panels generates 100 watts of electric power during sunny weather, assuming typical solar irradiance of 1,000 watts per square metre.
I thought I’d write a bit about my experiences experimenting with this solar panel and what I’ve learned.
The Manufacturer Didn’t Lie
I was delighted to see that the panel generated the full 10 watts of power mentioned by the manufacturer when I took it outside in typical sunny weather. I conducted multiple tests in weather of varying degrees of cloudiness. During one cloudy morning test, when the sun was barely noticeable through the clouds, the panel generated about 40% of its rated generation capacity.
During another test in which the sun was not visible at all, it generated 25% of its nameplate (generation) capacity, 2.5 watts.
Importance of Panel Tilt and Cell Shading
During most of my tests, the panel actually generated the most electricity when facing straight upwards, because of the sun’s position. Depending on the sun’s position, the panel will need to be tilted, and sometimes it needs to be pointed straight upwards. The power generated by the panel did vary considerably as I changed its position, so this is clearly important.
As always recommended, if you buy solar panels, ensure that they are placed where it is most sunny, and for the longest periods of time. If you can set up an affordable solar tracker, good for you. These maximize power yield.
This is one of the most important issues. Never shade a single cell of a solar panel (not even a little). Solar panels are usually made of a string of solar cells connected in series. I demonstrated this with my panel too.
If you are installing your own solar system, I would connect as few panels in series as possible to minimize the effect of this. But, don’t be deceived by the severity of this issue — if you place your panels in a section without shade, this is rarely going to be an issue, unless something splatters on the panel, in which case you would rinse it off.
During winter, you can use a roof rake to remove snow from your solar panels (if you live in a snowy climate).
To be more specific about the above, the first solar cell in the circuit generates electricity, it flows through the second cell, then the third, fourth, etc, until it exits the final cell and is used to charge batteries.
If you shade any of these cells, the electrical resistance of that cell obstructs the flow of current through the entire solar panel, and reduces the power output of the entire panel significantly.
Rinse off your solar panels periodically (even if it is a just some fruit on them). This maximizes power production.
I will continue to test this solar panel and use it to charge my USB electronics and other science projects for now.