Storage Tank Concept with Improved Dynamics for Complex Hydrides

Abstract

Hydrogen storage tanks based on complex hydrides (CxH) e.g. NaAlH4, usually show unsatisfactory tank dynamics due to poor intrinsic kinetics of the storage material. In general, high temperatures are necessary for the absorption process in order to overcome these kinetic limitations. With the approach presented in this paper, the absorption dynamics of the storage tank can be drastically improved without negative impact on the gravimetric or volumetric densities due to additional heating devices: A metal hydride (MeH) showing a lower equilibrium pressure but faster reaction kinetics than the CxH is added to the storage tank in order to initiate the reaction of the CxH by heating up the material in a fast exothermal reaction. Therefore, the complex hydride storage tank can be charged - even at low starting temperatures. In the presentation, this new concept will be explained with detailed simulations based on experimental results for reaction kinetics and physical bulk properties. Additionally, an optimal reactor configuration is being developed including the determination of the mass ratio of the MeH and the CxH. Based on the results of this work, slow intrinsic reaction kinetics at low temperatures of future complex hydrides will to some extend not hinder technical applications anymore.