Dual Axis Automatic Sun Tracking System for a Parabolic Solar Concentrator

Abstract

In India, solar energy is available in abundance and at no cost. The solar concentrators converge sun rays onto a smaller volume. These concentrators are used in many small-scale or domestic applications. A parabolic solar concentrator with an aperture diameter of 1.4 m and a focal length of 0.28 m is considered here. These concentrators need positioning as per the sun's position to maximize the concentration. For adjusting the correct position, an index pin is provided on the rim of the concentrator. The paper presents, an automatic sun-tracking system developed for the mentioned solar concentrator. Two pairs of light-dependent resistors (LDRs) are mounted in the plane normal to the index pin plane at a fixed distance from the pin centre. If two LDRs in a pair are equally illuminated then the difference in the output is zero. The resistance change of LDR is used to drive a motor to position the concentrator. Two high-torque DC motors, geared pulleys and belts are used for positioning the concentrator. Energy concentrated slowly varies as the sun traverses. Hence, position adjustment after about 20 minutes is found sufficient. Therefore, the tracking motors and associated circuitry are activated for 1 minute every 20 min. The power required for this circuit could be derived from a storage battery charged from a solar panel.