Gas-solid reactions for energy storage and conversion

Abstract

Reversible gas-solid reactions could offer relevant technological contributions to an energy system predominantly based on renewable energy. However, our current understanding of this technology is mainly based on fundamental material research and generic application concepts. Therefore, the first part of this work summarizes the current state of knowledge in order to identify unique advantages that could arise from reversible gas-solid reactions for energy storage and conversion. Starting with a technological differentiation between various reversible processes used for energy storage, a classification of different reactor designs and a generic approach for thermal integration and necessary reaction gas supply, three main directions are derived that currently seem most promising to transfer the specific properties of gas-solid reactions to technical systems: (1) open configurations to reduce system complexity, (2) utilization of available pressure differences to adjust the reaction temperature and (3) combination of abundant materials with the intrinsic possibility of lossless storage. Based on these considerations, the second part of this work summarizes our approach to transfer material properties to technical systems, e.g. by developing storages that utilize oxygen from air, by taking advantage of the pressure dependency of the reaction temperature of metal hydrides and salt hydrates or by combining the long-term energy storage possibility with abundant and costefficient reactants such as calcium oxide and water.