1 Development and Testing of a Two-axis Tracking Spherical Solar Cooker Md. Rafsunjani 1 , Erina Baynojir Joyee 2 , A. N. M. Mizanur Rahman 3,* 1,2 UG Student, 3 Professor Department of Mechanical Engineering, Khulna University of Engineering & Technology, Khulna 9203, Bangladesh drmizan84@gmail.com ; rafsunjanihemel@yahoo.com Abstract: Solar energy, the clean and non-polluting energy source, has a great potential to supply world’s energy needs. It is one of the largest renewable energy resources which is available almost everywhere. There are many fields where solar energy is used such as water & air heating, drying, distillation, cooking etc. But the efficiency of solar systems is less than conventional systems. It might be because of lack of proper technology and high cost to develop efficient system. Solar cooker is a device which is used for cooking food. It is simple, safe and convenient to cook food without consuming conventional fuel. In the previous year a parabolic type spherical solar cooker was designed and constructed. In that cooker, single axis manual tracking was used. In order to improve the efficiency of the cooker, a two axis tracking mechanism was designed and constructed and the cooker was installed on it. But, the motors that were needed for two axis tracking were expensive. So, an alternative manual tracking system was developed that could serve the purpose of facing the collector towards the sun every half an hour. Performance of the cooker has been measured. The maximum temperature inside the cooking pot was found to be 97˚C, with a load of 300 g rice and 100 g dal, within 40 minutes at a radiation level of 260-394 W/m 2 . Keywords: Solar cooking, spherical cooker, tracking system, two axis tracking, performance test. I. INTRODUCTION In developing country like Bangladesh, energy crisis is very serious. Natural energy resources such as fossil fuel, oil, natural gas etc. will be finished within very short time until new sources are explored. So, energy conservation by developing efficient energy systems and developing energy alternatives has become important consideration. This led to considerable research and significant progress has been made in this sector [1]. In some cases renewable energy is the most suitable solution for the growing energy demand. Among these energy sources, solar energy is the most widely available one. Solar energy has been utilized by human being since the dawn of civilization. Solar technology can be classified according to capture, conversion and distribution. Solar energy is cheap, abundantly available almost everywhere and can be used for various domestic as well as industrial applications like cooking, dehydration, drying, heating of water or air, power generation etc. Solar energy can be directly used for cooking. There are different types of solar cooking methods. For example, in box type solar cooker green house effect is used for cooking, in panel cookers transparent glass bowl along with a reflective panel is used, in parabolic dish cookers concentration of sunlight is used for cooking. In developing countries like Bangladesh energy consumption for cooking is a lion share of the total energy consumption. In the rural areas cooking is mainly made by fuel wood but in the urban areas this is served either by gaseous or liquid fuels. But, in most of the areas mainly fuel woods are used for cooking purpose which is a major cause of deforestation [2]. The sun moves from east to west across the sky within the day. Also, position of the sun varies in different seasons. If the payload can be moved with the movement of the sun, it gets more solar radiation. To get maximum solar radiation solar trackers are used. Solar tracking system is a device for orienting a solar collector or panel towards the sun all the time. Reflectors are devices to deflect the solar radiation towards a specified direction to increase the radiation intensity. Solar trackers are used to collect more solar energy. So, if a solar tracker is used in a solar cooker or any other device that uses solar energy, its efficiency will increase as the payload will get more radiation. In the previous year, a parabolic dish type solar cooker was constructed and tested [3]. In that cooker, a single axis manual east-west tracking system was used and after every 15 minutes interval the cooker was manually tracked. To overcome these limitations, attempts have been made to develop a two axis tracking system in the present work. Four LDR sensors were used for tracking the sun. Depending on the variation of light intensity, the sensors send signal to the control unit about the right position of the sun. The control unit sends signal to two motors (one is fixed with the vertical axis and the other fixed with the horizontal axis) for getting the most likely position i.e. perpendicular to the sun. The two motors would rotate the cooker until all the four sensors read equal resistance due to incident sunlight. II. THEORETICAL ASPECTS AND LITERATURE REVIEW The sun is the star of our planetary system and one of the largest stars in our galaxy. The source of energy in the sun is at its core where hydrogen is converted to helium in a thermonuclear reaction. This energy travels from core of the sun to its surface and then to the earth in two main forms, heat and light. Every hour enough sunlight reaches the earth to meet the world’s energy demand for the whole year. The