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P. Weinberger, D. Müller, C. Knoll, G. Gravogl:
"Thermochemical Energy Storage Materials - Reaction Principles and Possible Problems";
Vortrag: 7th European Conference on Renewable Energy Systems, Universidad Carlos III, Madrid (Spain); 10.06.2019 - 12.06.2019.

Aiming for a sustainable recycling of industrial process waste heat or a temporal heat storage in combination with solar-thermal heat production the use of high-performance thermochemical energy storage materials (TCES) can be a game changer in nowadays efforts for a significant reduction of fossil fuel consumption. Selected by a systematic algorithm-based database search for reversible solid-gas reactions several examples of material pairs will be presented. Each material is characterized on atomic scale using in-situ X-ray powder diffraction (P-XRD) as well as on particle scale using Scanning Electron Microscopy (SEM). Additionally, surface area characterization (BET) and Small Angle X-ray Scattering (SAXS) yields information on the particle morphology. The thermochemical solid-gas reactions are observed by Simultaneous Thermal Analysis (STA). Lab-scale reversible formation of the calcium oxalate hydrate from the anhydrate will be presented as a TCES material with excellent cycle stability within a temperature range of 25-200°C. For the temperature range between 920 - 980°C the redox couple CuO2/CuO under N2 or synthetic air features a remarkable cycle stability as well. In the presence of CO2 under elevated pressure up to 110 bar several metal oxides have been successfully carbonatized at temperatures below 100°C, and reversible reactions of NH3 with CuSO4 yields an extremely rapid performing TCES material. In this study we want to emphasize the importance of unambiguous materials characterization for the interpretation of thermochemical reactions in lab-scale reactors for a successful upscaling towards a prototype reactor.

Thermochemical energy storage; carbonatization reactions; hydratization reactions; salt hydrates; salt ammoniates