Environmental Reactivity of Solid-State Hydrogen Storage Systems: Fundamental Testing and Evaluation

There is extensive research being conducted in developing new hydrogen storage systems that have higher gravimetric and volumetric capacities.  However, less is understood about the hazards and risks associated with using and handling these materials.  Therefore, it is critical to develop appropriate risk mitigation strategies to handle unforeseen events such as a breach-of-tank scenario in order to design commercially safe condensed phase hydrogen storage systems.  A crucial aspect in risk identification is the development of rigorous environmental reactivity testing standards and procedures.   One way to accomplish this is by adopting a modified testing approach from the United Nations¹ testing procedure for the transportation of dangerous goods to evaluate a potential hydrogen storage material reactivity to air and water.  The modified U.N. procedures include identification of self-reactive, pyrophoric, and gas-emitting substances with water contact.  The results of these tests for air and water contact sensitivity will be compared for such hydrogen storage candidates as 2LiBH₄·MgH₂, NH₃BH₃, 8LiH·3Mg(NH₂)₂, and AlH₃.  The water contact tests are divided into two scenarios dependent on the hydride to water mole ratio and heat transport characteristics.  Air contact tests were conducted to determine whether a substance will spontaneously react with air in a packed or dispersed form. 

Additionally, thermodynamic calculations and substantiating calorimetric experiments were performed in order to quantify the energy released, energy release rates and to quantify the reaction products resulting from water and air exposure of various solid state systems.  These calorimetric measurements, performed on the “small scale”, were compared with standardized United Nations (UN) based tests for air and water reactivity and used to develop quantitative kinetic expressions for hydrolysis and air oxidation in these systems.  Furthermore, insight gained from these U.N. tests as well as isothermal calorimetry will allow the formulation of additional tests geared toward safety engineering, numerical simulation, and integration.

 

¹ DOT/UN Doc., Recommendations on the Transport of Dangerous Goods, Manual of Tests and Criteria, 3rd Revised Ed., ISBN 92-1-139068-0, (1999).