Operando flow regime diagnosis using acoustic emission in a polymer electrolyte membrane water electrolyser

Abstract

Polymer electrolyte membrane water electrolysers (PEMWE) are a key technology for producing clean ('green') hydrogen for decarbonisation of the transport sector and grid stabilization utilising increasing levels of renewable energy. Understanding the complex interplay of factors that affect device operation is key to improving the technology and advanced diagnostic techniques have a major role to play. In this work, acoustic emission analysis is used as a non-destructive, operando diagnostic tool to provide information about the relative number and size of gas bubbles generated locally within a PEMWE, providing effective characterization of the local flow regime. An optically transparent single-channel PEMWE is used to investigate the relationship between the acoustic signals obtained and the two-phase flow conditions inside the cell. Results show good correlation between the number of acoustic 'hits' and the number of bubbles passing through the flow channel. The size of bubbles is also shown to affect the average frequency of the hits. Consequently, the transition between flow regimes can be identified by acoustic emission analysis, paving the way for a simple, low-cost, nondestructive means of mapping flow inside commercial-scale PEMWEs.

Mass transport in polymer electrolyte membrane water electrolyser liquid-gas diffusion layers: A combined neutron imaging and X-ray computed tomography study

“…To do this, the land locations are focused on as the open flow channels are dominated by relatively unstable twophase flow with time-varying bubble dynamics, which precludes accurate analysis of the effective water thickness in the LGDL. Indeed, flow dynamics within channels have been extensively studied using optical cells [34,[40][41][42], but it is the particular ability of neutron imaging to examine water under lands and within porous structures that is exploited here [17,19].…”

Diagnosing Stagnant Gas Bubbles in a Polymer Electrolyte Membrane Water Electrolyser Using Acoustic Emission

“…In previous work, the authors demonstrated the ability of AE to detect changes in the number and size of bubbles passing through the flow channel of a PEMWE. This enabled the prediction of the change from bubbly to slug flow and showed that AE is a valuable operando tool for PEMWE diagnosis (Maier et al, 2019). Here, we demonstrate that AE signal changes dramatically when, rather than normal two-phase flow, stagnant bubbles are located within the vicinity of AE sensor.…”

“…This significant decrease of acoustic hits highlights a dramatic change of two-phase flow within the flow channels. The relationship between the number of acoustic hits and the number of bubbles passing through the flow channels has been established in previous work (Maier et al, 2019), which found that the number of acoustic hits scales directly with the number of bubbles passing through the flow channels. Hence, a drop in the number of acoustic hits indicates a decrease in the number of bubbles generated and passing through the flow channels, which is likely due to the blocking of the flow FIGURE 2 | Typical structure of an acoustic hit as voltage profile as a function of time.…”

“…The hit energy was determined by integrating the area under the waveform with respect to time. Further details on AE data analysis can be found in previous work (Maier et al, 2019).…”

Correlative study of microstructure and performance for porous transport layers in polymer electrolyte membrane water electrolysers by X-ray computed tomography and electrochemical characterization

“…Polymer electrolyte membrane water electrolysers (PEMWEs) are considered a highly promising technology for 'green' energy generation from renewable but intermittent energy sources such as solar and wind. PEMWEs possess several key advantages over conventional alkaline electrolysers, including high operational current density, high conversion efficiency, high purity of produced gases, rapid response, compact structure and high reliability [1][2][3][4][5][6][7]. Moreover, PEMWEs are robust and amenable to coupling with PEM fuel cells to create highly efficient regenerative energy storage systems.…”