One thousand thermal cycles of magnesium chloride hexahydrate as a promising PCM for indoor solar cooking

Cooking is the major necessity for people all over the world. It accounts for a major share of energy consumption in developing countries. There is a critical need for the development of alternative, appropriate, affordable methods of cooking for use in developing countries. There is a history for solar cooking since 1650 where they are broadly divided into direct or focusing type, box-type and indirect or advanced solar cookers. The advanced solar cookers have the advantage of being usable indoors and thus solve one of the problems, which impede the social acceptance of solar cookers. The advanced type solar cookers are employing additional solar units that increase the cost. Therefore, the solar cooker must contain a heat storage medium to store thermal energy for use during off-sunshine hours. The main aim of this paper is to investigate the influence of the melting/solidification fast thermal cycling of commercial grade magnesium chloride hexahydrate (MgCl2·6H2O) on its thermo-physical properties; such as melting point and latent heat of fusion, to be used as a storage medium inside solar cookers. One thousand cycles have been performed in a sealed container under the extra water principle. The thermo-physical properties are measured using the differential scanning calorimetric technique. It is indicated that MgCl2·6H2O with the extra water principle and hermetically sealing of the container is a promising phase change material (PCM) for cooking indoors and during law intensity solar radiation periods. It is also found from the melting/solidification behavior of MgCl2·6H2O that it is solidify almost without supercooling; except in few cases where it showed maximum of 0.1–3.5 °C of supercooling.

Research highlights
► Solar cookers must contain a PCM for cooking indoors.
► MgCl2.6H2O when it cycled in a sealed container.
► MgCl2.6H2O shows maximum of 0.1–3.5 °C of supercooling.
► MgCl2.6H2O is a promising PCM for thermal energy storage.