Macro-encapsulation and characterization of chloride based inorganic Phase change materials for high temperature thermal energy storage systems

[Display omitted] •A novel approach to encapsulate high temperature chloride based PCM is presented.•Low-cost ceramics with excellent thermal and chemical stability were used.•Ceramics sintered at 1190 °C did not show any reactivity with molten sodium chloride.•Capsules survived more than 150 thermal cycles.•No degradation in thermophysical properties of the capsules and PCM on cycling. A novel approach involving the use of ceramic materials was investigated for encapsulating chloride based PCMs with melting points higher than 650 °C. Low-cost ceramics with excellent thermal and chemical stability under molten-salt conditions were identified as the encapsulants. The processing procedure for these materials was discerned by systematic porosity distribution and materials compatibility studies. The influence of sintering temperature on the reactivity of feldspar, ball clay, kaolin and the mixture thereof with molten sodium chloride was investigated by IR spectroscopy. The porosity of the sintered ceramic samples was analyzed through water and dye absorption tests, as well as SEM analysis. The results were used for developing an optimum ceramic capsule fabrication procedure, which involved the use of a green ceramic body followed by sintering at 1190 °C. Sodium chloride and its eutectic with potassium chloride were used as the PCMs. The selected PCM was poured into and filled the fabricated ceramic capsule through a hole which was sealed at a temperature close to or higher than the melting temperature of the PCM. The fabricated capsules have been tested and have survived more than 150 thermal cycles without showing degradation in their thermo-physical properties.