Energetic evaluations of an electrochemical hydrogen compressor

Abstract

Hydrogen has been considered as the energy vector that could narrow the gap in the transition towards less polluting energy production. However, it faces compression and storage as technological challenges. Electrochemical hydrogen compression (EHC) is an interesting alternative since it demands low power consumption and could even separate hydrogen from a gas mixture. Therefore, it is necessary to conduct an energetic evaluation of the EHC related to its working conditions to establish the optimal ones in terms of efficiency. This work presents the evaluation and comparison of galvanostatic and potentiostatic operation modes of an EHC with a 50-bar pressure target. During the development of the experimental work, the values of the main overpotentials that affect an EHC were obtained: diffusion voltage, membrane voltage, activation overpotential, and contact overpotential. The highest actual work and power values were achieved at 0.215 V and 0.5 A/cm2 (potentiostatic and galvanostatic mode), while the lowest were obtained at 0.072 V and 0.1 A/cm2. This trend is reversed for voltage efficiency, reaching a maximum of 69.7 % for 0.072 V and a minimum of 19.9 % for 0.5 A/cm2. The calculated flow efficiency values were, for all cases, higher than 94 %, with a maximum efficiency of 99 % at operating conditions of 0.5 A/cm2 and 0.215 V. The global efficiencies of the EHC were also calculated, being more efficient when working in a potentiostatic mode, presenting values of 66 % at 0.072 V against 52 % at 0.1 A/cm2.