In order to track the sun as as the Earth rotates (or as the sun moves across the sky...) Greek technologist Costas Rooster has created a an Arduino-based device which calculates the position of the sun (in elevation and azimuth) and then positions a panel using motors and hydraulics to face the sun. It's an ideal base for solar-tracking devices and increasing the efficiency of solar panels. In the following video the entire process and result is quickly documented:
If this type of project is of interest, you will enjoy the book "Practical Arduino" by Jonathan Oxer and Hugh Blemings:
Using this book you can create your own Arduino-based designs, gain an in-depth knowledge of the architecture of Arduino, and learn the easy-to-use Arduino language all in the context of practical projects that you can build yourself at home. Get hands-on experience using a variety of projects and recipes for everything from home automation to test equipment. For more information and to order, click here.