Dr. Lea Huber
Experimental Investigation of Innovative Iron-Oxide Composites for a Thermochemical Hydrogen Storage
Limiting the consequences of anthropogenic climate change requires an increased usage of renewable energies in energy generation. However, regenerative energies like wind and solar energy are subjected to strong weather-related fluctuations. In order to maintain a secure energy supply, an increased integration of storage capacity is mandatory. In this context, especially hydrogen has proven to be an ideal energy carrier for a cross-sector energy supply.
An effective way to store hydrogen is the thermochemical storage system based on the iron/iron oxide reduction and oxidation (REDOX) process. This reversible storage process is an intermittent two-phase reaction, which takes place in a hydrogen atmosphere during the reduction (charging) or in a steam atmosphere during the oxidization (discharging) between 700°C and 900°C.
The main challenge facing this technology is the short lifetime of the storage materials due to the associated aging effects. This research work aims, therefore, at enhancing the life time of the storage materials by adding suitable supporting materials to the active iron/iron oxide materials. To this aim, composite mixtures of different iron oxides (99.1% Fe2O3, 97-99% Fe3O4) and supporting materials with a content of 10 wt% to 30 wt% were prepared and tested. The selected supporting materials differ in the composition of the main constituents of SiO2, CaO and Al2O3. Furthermore, spherical pellets and cylinder samples with and without compression were prepared to investigate the influence of the preparation method on the reaction behavior of the composite materials having different shapes and porosities. To evaluate the effects of the utilized supporting materials and the shape of the samples, the reaction kinetics were investigated using a thermo-gravimetric device (STA 449 – Jupiter F3) and the microscopic sample structure before and after repeated REDOX cycles (reduction in an 80%/20% hydrogen/nitrogen atmosphere and oxidization in an 80%/20% steam/nitrogen atmosphere) at 700 and 800 °C were analyzed.
hydrogen storage, thermochemical storage system, iron REDOX-reaction, iron oxide