An experimental study of employing organic phase change material for thermal management of metal hydride hydrogen storage

This paper presents the details of an experimental study of using a phase change material (PCM), made of 4.56 kg RT28HC paraffin wax, for self-contained thermal management of an 800 NL metal hydride (MH) hydrogen canister (MmNiMnCo). Thermal behaviour and charging/discharging performances of this innovative arrangement were investigated by considering the impacts of the operating parameters including hydrogen pressure, hydrogen flow rates, and effective thermal conductivity of PCM. Introducing PCM for thermal management of MH offered a possibility to store the heat released during hydrogen charging mode and transfer it back to the canister during discharging. The test results suggest that the total amount of hydrogen being utilised, while MH absorption/release rates being maintained at desired levels, is improved by two times after employing PCM for its thermal management. However, the maximum accumulative amount of hydrogen absorbed/released by the MH was still only up to 26 % of its total storage capacity with hydrogen charging rate dropped gradually after being started from 1.1 slpm. Recognising the low thermally conductivity of the PCM as the root cause of this shortfall, 10 PPI copper metal foam (MF) with 96 % porosity was embedded in the PCM. By introducing this MF, the full capacity of the MH canister could be utilised at continuous charging and discharging rates of 1.1 slpm and 1.5 slpm, respectively. • The effectiveness of using PCM for MH thermal management is experimentally investigated. • PCM can store heat released from MH during charging and transfer it back during discharging. • Only 26–29 % of MH storage capacity is utilised when employing pure organic PCM. • Full MH capacity can be used by using a PCM-metal foam composite for its thermal management.