Evaluation of the pressure dependence of the cycle durability and thermodynamics of a metal hydride compressor composed of ternary V40 and V70TiCr

In this study, the cycle durability and thermodynamic characteristics of V40TiCr and V70TiCr were examined to evaluate their performance as metal hydride compressors. The cycles of incomplete hydrogen absorption under low pressure increased the hysteresis in the higher hydrogen concentration region, wherein cycling was not conducted, thereby forming an unavailable region; however, the equilibrium absorption pressure recovered after several full cycles at higher pressure. Due to the thermodynamic evaluation after 300 full cycles, V40TiCr with 0.70, 0.53, and 0.44 of Ti/Cr ratio are expected to compress 1.2 wt% of hydrogen from 0.25 to 4.9 MPa, 1.96-22.2 MPa, and 5.97-46.8 MPa, respectively, between 40 and 150 degrees C. V70TiCr with a low Ti/Cr ratio (0.33) demonstrated good cycle durability and is expected to compress 1.7 wt% of hydrogen 10 times from 5.4 to 54.8 MPa between 35 and 155 degrees C. (c) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Automated summary

This study examined the cycle durability and thermodynamic characteristics of V40TiCr and V70TiCr to evaluate their performance as metal hydride compressors. It was found that incomplete hydrogen absorption cycles under low pressure increased hysteresis in the higher hydrogen concentration region, but the equilibrium absorption pressure recovered after several full cycles at higher pressure. V70TiCr with a low Ti/Cr ratio demonstrated good cycle durability and is expected to compress 1.7 wt% of hydrogen ten times from 5.4 to 54.8 MPa between 35 and 155 degrees C.