International Conference on Environmental Technology and Construction Engineering for Sustainable Development ICETCESD-2011, March 10-12, 2011, SUST, Sylhet, Bangladesh ___________________________________ Corresponding Author: Dr. Enamul Basher Email: enamul_basher@eee.buet.ac.bd A MICROCONTROLLER BASED AUTOMATIC SOLAR TRACKING SCHEME DR. ENAMUL BASHER 1 , MARZIA HOQUE TANIA 2 and MD. SAMIUL ALAM 2 1 Department of Electrical and Electronic Engineering, Bangladesh University of Engineering and Technology, Dhaka-1000, Bangladesh 2 Recent Graduate, Ahsanullah University of Science and Technology, Dhaka-1215, Bangladesh ABSTRACT A solar energy collecting surface performs best whenever it is faced to the sun. In this research, studies have been carried out to develop a microprocessor based automatic solar tracker locally with least cost. The system has been programmed to detect the intensity of sunlight by a differential arrangement of two photoresistors and subsequently actuate the motor to position the solar panel where it can receive maximum sunlight. This permits the solar panel moving from east to west and returning from west to the east, within the angle regulation range of 0-180° forward and reverse. The designed system can track the better sunlight position within 1 sec. This microcontroller based system with its auxiliaries and stepper motor drive arrangement made it interactive with high degree of dynamic and steady state stability. Key Words: Renewable energy, photovoltaic, solar tracking system, microcontroller, stepper motor, maximum power capture, closed-loop control. 1. INTRODUCTION Energy is one of the key building blocks of sustainable development. Even today one third of the world population does not have access to electricity and are not connected to the national grid. Solar, wind, and hydroelectric power not only produce minimal carbon emissions once the generating systems are in place, they also help reduce poverty through improved energy access in underserved areas. Photovoltaic (PV) system will need to play a significant role in the world’s energy mix in 2050 to help achieve global climate change goals at the lowest cost [1]. The International Energy Agency estimates that nearly 50% of global electricity supplies will need to come from renewable energy sources in order to halve carbon dioxide emissions by 2050 and minimize significant, irreversible climate change impacts [2]. Solar panels are generally statically aligned at lattitude tilt angle, they have a fixed position at that certain angle towards the sky; the time and intensity of direct sunlight falling upon the solar panel is greatly reduced, it results in low power output from the PV cells. In order to have maximum power capture throughout the day it is necessary that the photovoltaic panels change their orientation throughout the day following the path of the sun in the sky, this is