Omprakash Parida* et al. / (IJITR) INTERNATIONAL JOURNAL OF INNOVATIVE TECHNOLOGY AND RESEARCH Volume No. 1, Issue No. 2, February - March 2013, 201 - 206 ISSN 2320 –5547 @ 2013 http://www.ijitr.com All rights Reserved. Page | 201 Night Cooking Solar Cooker Using Molten Sodium Chloride as Phase Change Material OMPRAKASH PARIDA Silicon Institue of Technology Bhubaneswar,India SWASTIK TRIPATHY Silicon Institue of Technology Bhubaneswar,India JITENDRA KUMAR DASH Silicon Institue of Technology Bhubaneswar,India Abstract— Solar cooking technology has to undergo a sea change if at all it’s to be accepted as the main source of cooking Energy. This is why a better model that incorporates both the traditional heat trapping cum concentrator mechanism and the latest techniques like that which uses a solar battery (phase change materials with high heat retention capability) can be used as the basic idea for the purpose. A multi-purpose hybrid solar cooker using locally available materials can be used for night as well as day cooking. It will have two way supply of heat directly from sun during day time for cooking and from the phase change material during night time. This cooker preferably provides indoor cooking and it can have two arrangements, namely Grill and Oven, for cooking various Indian foods. Sufficient care was taken for selecting the materials to be used in this solar cooker with price and availability constraints across rural India. The design ideally can cook two traditional meals a day for a family of five. All assumptions for the design are based on this basic aim. I. INTRODUCTION Solar cooking with all its benefits, starting from environment-friendliness to its cost effectiveness, is yet to be accepted as a viable option for cooking. The main reason for this can be traced out as; 1. Cooking occurs only in sunshine hours. 2. No ease of cooking as the user has to wait longer for simple cooking processes like boiling. 3. Limited number of dishes that can be cooked. While in the day time cooking will not be an issue, for the night there has to be some form of back-up energy stored throughout the day. This is achieved by selecting a material that has high heat retention capability. However recent studies show that sensible heating is not the option, even if the material has a high Specific Heat. This is why we opted for Latent Heat storage using phase change materials. Latent heat storage is a relatively new area of research which can be used for storing heat by changing the phase of the material (phase change material-PCM) without rise in its temperature. To improve the ease of cooking one must separate the traditional model of a solar cooker that has its absorber, cooking surface and heat storage system all jammed to the same place. We can implement the design by having an outdoor arrangement for heat absorption and storage that includes the Phase Change Material, a heat exchanger with water-glycol solution as its fluid which is regulated by a condenser and steam tank, and finally an indoor cooker installed inside the kitchen. II. PRINCIPLE OF NIGHT-COOKING The traditional demerits of the solar cookers of indequate energy back-up at night limit its operation time to sunshine hours only. However by using a few basic thermodynamic principles we can be able to remove these limitations to greater extents. These are- (a) Latent Heat Storage ,(b) Thermosiphon principle,(c) Steam Cooking Principle, (d) Heat Exchanger. A. Latent Heat Storage: Latent Heat is the quantity of heat stored by a material before any change of phase at a constant temperature and pressure. This Latent Heat could be used to store heat for cooking at night time. Sensible Heat cannot be used for the same purpose as the material supplying its sensible heat tends to lose its conductivity with falling temperature. The material that is used to store heat is termed as the Phase Change Material. It should have a preferably high value of Latent Heat Capacity for heat Storage. We chose Sodium Chloride as the Phase Change Material because of its high Latent Heat Capacity (492kJ/kg) and ease of availability. However its considerably high melting point of 802 °C requires a number of solar concentrators to produce the requisite heat. B. Thermosiphon: Thermosiphon refers to a method of passive heat exchange based on natural convection which circulates liquid without the necessity of a mechanical pump.The buoyancy of the already hot water layer is used to generate a flow of water that leads to convection. Its intended purpose is to simplify the pumping of liquid and/or heat transfer, by avoiding the cost and complexity of a conventional liquid pump. C. Steam Cooking: It is the use of steam as the source of heat for cooking.