Hi guys, I was thinking of doing my science fair project on how mirrors and other light reflectors can help increase the efficiency and reliability of solar panels, I was thinking of using a 20 watt 12v solar panel, and implement a solar tracking feature on it, with 2 nema 17 motors with a gear ratio, I would also add mirrors on the sides of the solar panel, where they could be adjusted with micro servos, all of this to test the difference in the efficiency of the solar panel when having the mirrors on. I just have a couple of questions.
Do you think it is liable to run the whole system off the solar panel?
How much current to the nema steppers draw when they are not moving?
If you cannot even run the system off the solar panel, it would be a bad idea to build the system in the first place. After all you want to get energy out of it to sell.
Stepper motors do not require energy when not moving. You simply switch off the driving circuit and get a very small amount of current flowing. You can check the datasheet of the circuits for cutoff currents. It’s likely around 1/1000 times the active current.
The question of mirrors has likely been investigated before. There are power station concepts with mirrors. So far, I have not seen any with semiconductor panels. I would investigate if this is even an option. The solar panel manufacturer builds the panels for planet earth. If you add mirrors it will more likely be like on mercury. The panel needs to get rid of heat. So, if you live in a sunny place be careful not to fry your panel.
Klaus_K:
Stepper motors do not require energy when not moving. You simply switch off the driving circuit and get a very small amount of current flowing.
Depending on your mechanical construction you do risk losing position. You'd need a worm drive of sorts.
Servos are anyway more sensible for this application, as you normally want to turn left/right within a limited range. No need to have those mirrors or panels make full turns (unless you live above the polar circle of course).
You should be able to get more power out if you track than if you don't but it may not be much.
You also want to consider if you will track the brightest part of the sky or calculate where the sun is, the two are not the same.
If you are using mirrors I suppose you need to check that they reflect the part of the spectrum the panels convert into electricity. Instead of moving the panels using heliostats to reflect the sun onto the panels might be an option. Overheating the panels might be another consideration, I am just wondering if their efficiency drops as their temperature rises.
I have played quite a bit with exactly the same 20W panel, as well with a smaller ones.
In summer and days without clouds, you can get full power from it. However, clouds, even birds flyover may drop it radically. Since that, it is not reliable to power continuously anything just on solar power, except the battery packs and from the battery packs to power any device.
As well, in summer, temperature of the panel is quite high, perhaps 70C or more. In case of additional mirrors, temperature is multiplied by number of mirrors, in which case panel will hardly survive, but anyway you cannot get more power from it than maximum specified. Of course, in other seasons, mirrors could be of great help to get near maximum efficiency.
Check for "Solar furnace" to learn how solar energy can be used at quite different level, but that is not related much for your fair project (except usage of mirrors).
So let's just say that while there are some systems where the panel itself tracks the sun for maximum efficiency, you simply do not see commercial systems using mirrors.
And the need to keep the panels cool is a major reason as efficiency does drop off with heat.