The commercially available tracking systems make use of servomotors with feedback controllers, and add substantially to the overall cost of a solar energy system. They also require a power supply, and a sophisticated level of maintenance. Since the Solar energy devices are important for applications in decentralized systems, which are usually located in remote and rural areas, these two requirements are often not met. Consequently, tracking is normally dispensed with.
To overcome these limitations, we have developed a clock-controlled mechanism for tracking the Sun. In this mechanism the collector is driven by a counterweight by means of a steel cable whose rate of release is governed by the escape mechanism of a conventional alarm clock. In this system the collectors are mounted in a symmetrical fashion to minimize the effect of wind gusts. A prototype of the system has been fabricated and tested over nearly three years. The system tracks the sun within 0.5 degrees throughout the day.
The design features enable a simple fabrication procedure, and the overall cost of the tracking system is negligible in comparison with the cost of the PV modules. The cost of the system fabricated in our laboratory is less than rupees five hundred only. The cost of the system can be considerably lowered by mass production.
Source : http://www.iitkgp.ac.in