I miss one thing in this discussion. Many suggestions have been made re tracking the sun, NONE re avoiding mindless hunting when the sun is hidden. Mahmood, I'm afraid you will need to combine calender/clock math and tracking to optimize this. My first thought re this would be to use simplified calender/clock math to create a window the tracker should stay within, then whenever the sun disappeared have a tracking algorithm that tried to track the invisible sun, the once an hour? if no sun was seen run a loop inside the window. Thius, of course could be problematic if the sun was not seen rise, so ypu must remember 'last good sunrise' and interpolate from that wher to start the next day.

OK, just babbling, but I hope you will go through such thoughts before you embark on your solar journey.

Erik