Characterization of hydride forming materials at sub-zero temperatures

GENTILE M.; BORZONE E.M.; BARUJ A.; MEYER G.O.

Río de Janeiro

Congreso; 22nd World Hydrogen Energy Conference; 2018

International Association for Hydrogen Energy

Mountain areas with important snow accumulation presentavalanche danger to both infrastructure and human life in scenarios such asroad cleaning, mining and winter sport resorts. To minimize the risk associatedwith these random events, a usual practice is to perform controlled explosionsat a convenient timing to promote smaller avalanches and prevent the build-upof dangerous situations. Hydrogen is sometimes used as fuel to produce such controlleddetonations. Hydrogenis a clean fuel because the products of its reaction with oxygen are innocuousto the environment. The possibility of using hydride forming materials (HFM) inthis kind of environment to store this hydrogen is a novel idea. HFM areattractive for safety reasons, as they offer high volumetric density storage ofhydrogen at low pressure. Moreover, hydrogen pressure is almost constant duringhydride formation (charge) and decomposition (discharge), facilitating thedesign of technological applications.In particular, we have contacted Catedral Alta Patagonia SA, a company managing an important ski resort, for designing a process and an equipment for hydrogen storage using HFM, and supplying it at an adequate pressure (over 100 kPa) at the environment temperature (down to -20°C). As most usual technological applications of HFM are designed to work at room temperature or higher, there is a lack of information about the HFM-hydrogen reaction at subzero temperatures.We propose to perform the hydrogen storage using HFM of theAB5 family. We present the characterization of samples prepared bymelting in an arc furnace, with composition LaNi5, MmNi5and MmNi5-xSnx (Mm: mischmetal). We studied theequilibrium and kinetics properties of the hydrogen absorption and desorptionreaction in the temperature range from -24°C to 40°C. Partial substitution ofMm with La, or that of Ni with Sn, reduce the absorption equilibrium pressure downto 1000 kPa while maintaining the hydride decomposition pressure higher than100 kPa. We determined the reaction enthalpy ΔH and entropy ΔS changes. The obtainedresults show that the use of these materials for the proposed application isfeasible.