Metal Hydrides

Automotive hydrogen storage systems require a significant increase in the volumetric storage density of hydrogen to provide the necessary range for ordinary use. Solid storage can provide significant increases in volumetric storage capacity of hydrogen at ambient temperatures. In this multi-year collaboration with General Motors, we used TiCrMn as a representative material to investigate:

• Thermal transport restrictions in activated metal hydride powder beds
• Additives to enhance thermal conductivity
• Interactions between thermal and kinetic limitations during tank fueling cycle
• Model development of hydride bed transport phenomena
• Heat exchanger design for metal hydride systems

The overall objective of the proposed program is to develop a magnesium hydride based storage system with rapid kinetics and high storage capacity. The Purdue effort is dedicated to the characterization of the heat and mass transport processes in a representative packed hydride bed.

Magnesium hydride offers the potential of up to 7.6 wt.% hydrogen, one of the highest capacities of any metal hydride. However, the high stability of the hydride phase necessitates operation at elevated temperatures and the addition of catalysts, both of which reduce the overall hydrogen storage density. Researchers at ITRI have developed catalysts that can improve kinetics considerably, which will be combined with the thermal analysis done by Purdue to produce a feasible system.

An object-oriented metal hydride MATLAB toolbox has been developed to help create more robust models for thermodynamic equilibrium, reaction rates, and thermophysical properties. During its development, a database of over 300 hydrides was assembled and identified over 1800 hydride pairs with coefficients of performance (COP) greater than 1. Lastly, we used a hydride pair scoring system to help focus on top pairs.