radman:
Time of day and year along with your latitude and longitude will tell you where the sun is, so essentially rotating based on time will do it.
I want build something that points to where the sun is myself, but I keep getting distracted.Another idea would be to have the panels facing south but static and use moving mirrors or heliostats to reflect additional light onto the panels - that would certainly look cool. Actually cooling the solar panels may make them more efficient perhaps with a heat sink or if there is running water available.
Interesting idea with lots of options for implementation... GPS would be good for time and position, if this project were to function in any location. Add some (or a lot!) of sun positioning data via SD card.
I know that would be much more complex than it needs to be, but I can't help it!