International Journal of Emerging Technology and Advanced Engineering Website: www.ijetae.com (ISSN 2250-2459, Volume 2, Issue 9, September 2012) 81 Calculation of Sun Position and Tracking the Path of Sun for a Particular Geographical Location Saheli Ray 1 1 Department of Electrical Engineering, National Institute of Technology, Agartala Abstract— Solar energy is one of the freely available renewable sources of energy and abundant in almost every part of the world. It is the most fundamental among the alternative sources of energy. With a view to collect energy from the sun, it is necessary to predict the sun position relative to the collection device. In this paper, an attempt has been taken to track the exact location of the sun for any geographical location of the earth. MATLAB software has been used to track the sun path and corresponding information such as sunrise and sunset. Here, the location of Silchar in the state of Assam of north-eastern India has been considered Keywords— Altitude angle, azimuth angle, latitude, solar energy, solar time, standard meridian. I. INTRODUCTION Solar energy has the greatest potential of all the sources of renewable energy [1]. Human life and all other forms of life on our planet are completely dependent on the daily flow of solar energy. For ages, man has been trying to harness the sun as an important source of energy. The best utilization of the solar energy will be when the path of the sun can be tracked. II. BASIC EARTH-SUN ANGLES The position of a point P on the earth’s surface with respect to the sun’s rays is known at any instant if the latitude, l, and hour angle, h, for the point, and the sun’s declination angle, d, are known. It is explained in Figure 1 [2]. Fig.1 Latitude, hour angle and Sun’s declination angles A. Latitude Latitude, l, is the angular distance of the point P north (or south) of the equator. It is the angle between OP and the projection of OP on the equatorial plane [2]. The centre of the earth is denoted by O. North latitudes are considered positive and south latitudes are considered negative. B. Hour Angle The hour angle, h, is the angle measured in the earth’s equatorial plane between the projection of OP and the projection of a line from the centre of the sun to the centre of the earth. It is measure from local solar noon, being positive in the morning and negative in the afternoon [1]. One hour of time is represented by 360/24=15 degrees of hour angle. C. Delination Angle The plane that includes the earth's equator is called the equatorial plane. If a line is drawn between the center of the earth and the sun, the angle between this line and the earth's equatorial plane is called the declination.[3].The declination is positive when the sun’s rays are north of the equator and negative when they are south of the equator. At the time of winter solstice, the sun’s rays are 23.5 degrees south of the earth’s equator and the sun’s rays are 23.5 degrees north of the earth’s equator At the time of the summer solstice. The sun’s declination is zero at the two equinoxes. The declination angle is given by d=23.45 sin [360/365(284+n)] (degrees) where n is the day of the year. III. RELATION BETWEEN CLOCK TIME AND SOLAR TIME Calculation of sun position must be made in terms of solar time. In order to know sun position, we are to convert local clock time into solar time. The conversion between solar time and clock time requires knowledge of the location, the day of the year, and the standards to which local clocks are set [4]. Time of Greenwich meridian (zero longitude) is known as Greenwich Civil Time or Universal Time.