Advancement of system designs and key engineering technologies for materials-based hydrogen storage

Hydrogen Storage Engineering Center of Excellence Metal Hydride Final Report

“…Some of the heat transfer improvement is attributed to reducing the contact resistance between the pellet and the container as well as the neighboring pellets. UTRC [28] also found a similar, about 50% reduction in volume expansion in experiments, with confined NaAlH 4 pellets on heat exchanger tubes after about 15 cycles and discussed the need for additional work on further reducing the contact resistance between the materials and the system. Some of the results of incorporating the engineered material properties into heat transfer and system models by UTRC and other HSECoE members will be discussed in more detail in the next section.…”

“…The rate of hydrogen absorption and desorption was also measured and the increased initial density of the compact was found not to adversely affect the rate. More detail and information on the UTRC studies can be found in references [27,28]. GM performed similar studies [29,30] to engineer the properties of compacted NaAlH 4 pellets with similar results.…”

“…The HSECoE was created to modify and engineer the available materials and to engineer new storage system designs to better assess the available materials against the system level targets. As part of this effort, HSECoE partners, UTRC [27,28] and GM [29,30], undertook material engineering studies to…”

“…UTRC also measured the thermal conductivity of the compact in both the axial and radial direction but did not find an appreciable difference. In another part of the study UTRC [28] switched from ENG powder to ENG "worms", which as the name implies are longer thread-like graphite materials. The thermal conductivity in the radial direction for the case of 5% ENG work was measured as 10.8 W/m/K versus only 1.54 W/m/K in the axial direction.…”