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We investigate pairs of compounds to be used as thermochemical energy storage, e.g. salt hydrates or redox active metal oxides. The crucial factor for a sustainable use for thermal energy storage is a high cycle stability combined with a robust reversibility of the solid-gas reaction.

Tuning the performance of MgO for thermochemical energy storage by dehydration – From fundamentals to phase impurities

Systematic variation of the dehydration temperature and time enables the preparation of highly reactive magnesium oxide for thermochemical energy storage purposes. The reactivity of the MgO, resulting from varying dehydration conditions has been studied by a comparative approach, including reactive surface area, particle morphology and reactivity towards rehydration. For the rehydration an in-situ powder X-Ray diffraction setup is used, allowing for continuous monitoring of Mg(OH)2 formation. The outcome of this investigation was subsequently applied to MgO from natural magnesites to assess the impact of impurities in the material on rehydration reactivity.

“Tuning the performance of MgO for thermochemical energy storage by dehydration – From fundamentals to phase impurities”, D. Müller, C. Knoll, G. Gravogl, W. Artner, J. Welch, E. Eitenberger, G. Friedbacher, M. Schreiner, M. Harasek, K. Hradil, A. Werner, R. Miletich, P. Weinberger, Applied Energy 253, 2019, 113562
https://doi.org/10.1016/j.apenergy.2019.113562

Pressure effects on the carbonation of MeO (Me=Co, Mn, Pb, Zn) for thermochemical energy storage

Metal carbonates are attractive materials for combining carbon capture and thermochemical energy storage. Carbonate materials feature high decomposition and formation temperatures and may be considered in applications in combination with concentrating solar power. In the present study in-situ P-XRD carbonation (1–8 bar CO2) and reactor-based experiments (1–55 bar CO2) are combined focusing on the effect of elevated CO2 pressures on carbonation of metal oxides. Carbonation of MnO and PbO at CO2 pressures between 8 and 50 bar in the presence of moisture resulted in reaction with CO2, forming the corresponding carbonates at notably lower temperatures than under dry CO2 atmosphere of 1 bar. This enables the application of metal oxide/metal carbonate reaction couples for energy storage at temperatures between 25 and 500 °C. Based on the reversible carbonation/decarbonation of PbO under varying CO2 pressures, an isothermal storage cycle between PbO/PbCO3 · 2 PbO, triggered by changing the CO2 pressure between 2 and 8 bar, was developed.

„Pressure effects on the carbonation of MeO (Me=Co, Mn, Pb, Zn) for thermochemical energy storage“, G. Gravogl, C. Knoll, W. Artner, J. Welch, E. Eitenberger, G. Friedbacher, M. Harasek, K. Hradil, A. Werner, P. Weinberger, D. Müller, R. Miletich, Applied Energy 252, 2019, 113451
https://doi.org/10.1016/j.apenergy.2019.113451