Hydrogen Charging Process of a Metal Hydride Hydrogen Storage System Using Phase Change Material for Self-Contained Thermal Management

Employing the phase change material (PCM) to store heat released from metal hydride (MH) canister during hydrogen charging and transfer it back to the canister during discharging process offers a potential to be self-contained thermal management for MH without using external energy. In this study, an experiment system was set-up by using 4.6 kg of RT28HC paraffin wax for thermal management during hydrogen charging and discharging processes of 800 NL MmNiMnCo metal hydride hydrogen storage canister. The performance of hydrogen charging of the MH hydrogen storage system will be investigated by controlling inlet hydrogen flow rate at the level that usually served by electrolyze in the solar-hydrogen system. The experimental results showed that due to low thermal conductivity of the pure PCM, the MH could not maintain the charging hydrogen at the rate as required to maximize the usage of hydrogen storage capacity of canister. It was found that the accumulative amount of hydrogen absorbed accounts for only 26%, 21% and 15% of total storage capacity of MH when charging hydrogen at the rates of 1.1, 1.5 and 2 slpm, respectively. Heat transfer enhancement for PCM is required to guarantee the right rates of hydrogen absorption and release during charging and discharging processes.