A hydrogen-compression system using porous metal hydride pellets of LaNi5-xAlx

The objective of this study is to examine the performance of a hydrogen compressor by using recently developed porous metal hydride compact technology exhibiting high thermal conductance. The inlet temperatures of the cooling medium for hydrogen storage (20 and 30 degrees C), the heating medium for compression (60, 70, 80, and 90 degrees C), and the kind of metal hydride (LaNi5 and LaNi4.75Al0.25) were considered as key parameters. For each condition, transient temperature distributions and compressed pressures were monitored. Results showed that the hydrogen compressor fared better at lower storage temperatures. The research showed that LaNi4.75Al0.25 had a faster absorption rate than LaNi5. In addition, the compression ratio was found to be primarily dependent on the temperature difference between cooling and heating; the compression work and the efficiency of the LaNi5 reactor were slightly larger than those of the LaNi4.75Al0.25 reactor. Under the considered conditions, the maximum work (2.44kJ) and efficiency (5.91%) occurred when LaNi5 operated at cooling temperature of 20 degrees C and heating temperature of 90 degrees C. (C) 2007 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.