Abstract

In this work an improved methodology for the study of hydrogen storage material (HSM) is presented, for the characterization of smaller samples of HSM at increased accuracy. It includes: the realization of innovative differential instrument; a novel approach to the detailed micro kinetic modelling; increase the comprehension of absorption and desorption mechanisms; support research efforts in this topic. As side results, a macro and lumped model for the design of generic hydrogen storage tank are developed and validated. The study of a novel IDA (Isochoric Differential apparatus) is presented, describing all the steps from the initial theoretical approach, to the detailed design and the definition of an experimental proceeding. It includes the necessary technical improvements to increase the measure uncertainty compared to the classical SIevert. Novel microkinetic modelling for HSM is explained as variation of classic nucleation and growth model (JMAK model). The nuclei’s growth is assumed to be limited by surface or even by radius of powder’s particles. Micro modelling is applied on Mg-based material, introducing high accurate kinetic measures obtained by IDA. This leads to extrapolate information about kinetic parameters and kinetic mechanisms of hydrogen sorption. The obtained micro modelling is used as core for the development of a model at a higher scale (macro) which keeps in consideration also heat and hydrogen diffusion in porous materials typical in hydrogen storage tank. Experimental data collected by a prototipal realization of hydrogen storage tank are used to validate macro modelling. Moreover, a lumped model is developed with the scope to built a numerical tool able to give preliminary indications on proper design/layout of hydrogen storage tank, based on hydrogen flow, temperature or pressure requirements. Lumped modelling is finally compared with results by the numerical simulation of validated macro model. Finally, micro kinetic model is applied on high accuracy sorption data (by IDA) on innovative catalysed Mg-material. Material is produced by a novel approach, where catalyst, Nb2O5, is deposited by PVD techniques at extremely low concentration on the surface of powder to exploit its higher catalyst proprieties.