I thought this ingenious invention might interest some folk on here:
The SunSaluter is a solar panel rotator designed for the developing world. Using only the power of gravity with a water clock, the SunSaluter enables a solar panel to passively follow the sun throughout the day, boosting energy output by 30% and producing four liters of clean drinking water.
Principle: water clock, see-saw balance. Water drips from a bottle through a mechanical filter, reducing its weight and continuously swaying the solar panel. Needs to be refilled in the morning of course.
By the way, the thumbnail pic shows a misadjusted one, that solar panel is very much not facing the sun.