Development of solid-state hydrogen storage solutions that are reliable, compact and efficient in terms of loading time and energy efficiency. – SOLHYSTORE

SOLHYSTORE aims to promote solid hydrogen storage by pooling the skills of a NEEL team renowned for its experience in the field of metal hydrides and the strategic vision developed by MINCATEC to meet the growing demand for hydrogen storage solutions that are safe, reliable, compact and efficient in terms of charging time and energy efficiency.
The first line of research concerns the formulation of metal hydrides, with a view to establishing correlations between composition and sorption properties. In the short term, the aim is to increase the thermodynamic equilibrium pressure of AB2-type hydrides, since commercially available compounds have a desorption pressure too low to meet the needs of certain applications. In the medium term, the aim will be to reduce the production cost of hydrides, which is the main obstacle to the development of a competitive storage solution. In the longer term, the focus will be on new, more performant hydrides, and/or hydrides meeting specific application needs.
A second focus is on the stability of sorption properties during charge/discharge cycles. To be competitive, storage devices must be able to undergo several thousand cycles without significant degradation of their sorption properties. The aim will be to identify hydride degradation mechanisms as a function of applied conditions, hydrogen purity and moisture content, in order to define compatibility thresholds based on the targeted number of hydrogen cycles.
A third area of research concerns the thermal management of tanks. Hydrogen absorption is highly exothermic, causing a sudden rise in temperature until thermodynamic equilibrium is reached. The progress of the reaction then depends on the dissipation of the released heat. To reduce the loading time, which is directly correlated with the efficiency of heat exchanges, we will be seeking to increase the effective thermal conductivity of metal hydrides. By modeling heat and fluid exchanges, we can identify limiting factors and optimize tank geometry, heat exchanger sizing and thermal fluid flow rates. To be reliable, modelling will have to be based on the measurement of various thermal parameters in situ under hydrogen pressure. The codes will then be validated by comparison with the experimental behavior of tanks developed by MINCATEC, to provide reliable predictions within 2-3 years.
A fourth area of research concerns the control of metal hydride expansion caused by crystallographic lattice dilatation due to hydrogen absorption. The theoretical volume change expected with AB2 compounds is of the order of 20%. This increase is partly absorbed by the porosity of the granular medium, but can nevertheless lead to significant mechanical stresses on tank walls. This is an essential point of vigilance, which has an impact on loading rates and tank sizing. We will seek to quantify and analyze the mechanical behavior of hydrides as a function of composition, compaction rate and additives introduced to increase thermal conductivity.
The final area concerns Life Cycle Assessment (LCA). An initial assessment will be carried out in the first year in order to guide our choices and reduce as far as possible the proportion of critical materials in the compositions selected. In the longer term, we will be seeking to develop protocols for passivating used tanks (pyrophoric powders), or regenerating metal hydrides that have been degraded, to enable a circular economy for tanks developed by MINCATEC.