Salt hydrates as alternative thermochemical energy storage materials for industrial applications

Abstract

Around 50 % of the global demand of primary energy is devoted to heat production, making heat the most abundant form of energy. A great part of the heat produced, is after the desired usage lost as low-grade waste heat. In order to increase energy efficiency, thermochemical energy storage is a promising technique to utilize and store the otherwise lost waste heat for later usage.In this thesis the synthesis and characterization of promising salt hydrates as thermochemical materials is presented. A small library of calcium dicarboxylate salt hydrates was prepared to investigate and compare these compounds with each other to scan for promising candidates and get a deeper understanding of the chemical processes behind the de- and rehydration reactions.Ca-terephthalate trihydrate has shown its potential as thermochemical material, showing a high storage potential, as well as good preliminary cycle stability results. A comparison with its derivatives resulted in the identification of the crystal structure of 2-fluoro calcium terephthalate trihydrate that could be investigated in collaboration with Priv.-Doz. Dr. Berthold Stöger.Furthermore, the synthesis of ettringite, another promising material, had to be optimized.The work can be considered successful, as a small library of 11 Ca-salts was prepared and characterized. Furthermore, the preparation method of ettringite could be optimized to a phase purity of 98.5 % confirmed with quantitative phase analysis for smaller scales.