Experimental investigation of coupling phenomena in polymer electrolyte fuel cell stacks

Santis, Marco; Freunberger, Stefan; Papra, Matthias; Wokaun, Alexander; Büchi, Félix N.

doi:10.1016/j.jpowsour.2006.06.007

Cited by 39 publications

(24 citation statements)

References 8 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This suggests that these changes in current distribution were produced from local variations in concentrations of hydrogen and oxygen and were not directly related to local water content in the GDL or membrane. In-plane currents resulting from local variations in a fuel cell system have been observed in the bipolar plates of fuel cells stacks 36,37 and in a cell with segmented electrodes that were connected through a bipolar plate. 38 The large redistribution we observed was not expected in our cell, though, because the segments are electrically isolated except through the GDL.…”

mentioning

confidence: 99%

“…We propose that the current redistribution is due to lateral currents that result from the changes in the potential distribution associated with the depletion of the reactants. [36][37][38] When the reactant flows were reduced to partially starve the fuel cell, the upstream electrode segments are at higher potential differences than the down stream electrode segments. This causes the currents to be concentrated in the upstream electrode segments.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Drops, slugs, and flooding in polymer electrolyte membrane fuel cells

et al. 2008

View full text Add to dashboard Cite

in Wiley InterScience (www.interscience.wiley.com).The process of flooding has been examined with a single-channel fuel cell that permits direct observation of liquid water motion and local current density. As product water flows through the largest pores in the hydrophobic GDL, drops detach from the surface, aggregate, and form slugs. Flooding in polymer electrolyte membrane (PEM) fuel cells occurs when liquid water slugs accumulate in the gas flow channel, inhibiting reactant transport. Because of the importance of gravity, we observe different characteristics with different orientations of the flow channels. Liquid water may fall away from the GDL and be pushed out with minimal effect on the local current density, accumulate on the GDL surface and cause local fluctuations, or become a pulsating flow of liquid slugs and cause periodic oscillations. We show that flooding in PEM fuel cells is gravity-dependent and the local current densities depend on dynamics of liquid slugs moving through the flow channels. 2008 American Institute of Chemical Engineers AIChE J, 54: [1313][1314][1315][1316][1317][1318][1319][1320][1321][1322][1323][1324][1325][1326][1327][1328][1329][1330][1331][1332] 2008 Keywords: multi-phase flow, fuel cells, porous media, transport IntroductionPerhaps the greatest challenge facing fuel cells is the difficulty in maintaining stable operation and control due to flooding by liquid water. The build up of water produced at the membrane/cathode interface is known to limit the current output from PEM fuel cells. To describe the effects of flooding, several models have been proposed. [1][2][3][4][5][6] Most of these hypothesize that liquid water condenses in the pores of the gas diffusion layer (GDL) creating a mass transfer resistance for oxygen to get to the membrane/electrode interface as illustrated in Figure 1.Our group recently examined water permeation through the GDL and obtained results that contradicted the previous hypotheses about liquid flooding. 7 The GDL is a woven cloth or paper of carbon fibers that is usually treated with Teflon 1 to increase its hydrophobicity. We showed that water does not enter the GDL until a sufficient hydraulic pressure is applied to overcome the repulsive surface energy. The largest pores in the GDL are the first to permit water penetration, and once water penetrates the pores it can freely drain. Our results suggested a two-highway system for liquid and gas transport through the GDL, as illustrated in Figure 2. Liquid is driven by a hydraulic pressure from the membrane/cathode interface through the largest pores while gas moves from the gas flow channel to the membrane/cathode interface through smaller, but more plentiful, pores. Results that support these conclusions have also been reported using florescence microscopy to view the ex-situ transport of water through carbon paper. 8 Recently, water intrusion has been used to determine the capillary pressure vs. liquid saturation curves for different GDL materials 9,10 , providing pore volume distributions...

show abstract

mentioning

confidence: 99%

mentioning

confidence: 99%

Drops, slugs, and flooding in polymer electrolyte membrane fuel cells

et al. 2008

View full text Add to dashboard Cite

show abstract

“…Also, the large thermal anomaly case does not lead to significant changes in current density. A different situation in which a large thermal anomaly does not lead to significant changes in local current density in the stack setting is shown experimentally in recent work [31].…”

Section: Future Validationmentioning

confidence: 84%

Reduced dimensional computational models of polymer electrolyte membrane fuel cell stacks

Chang

Kim

Promislow

et al. 2007

Journal of Computational Physics

View full text Add to dashboard Cite

“…Upon removal of the load, the OCV of cells 11-13 remained low, suggesting pin-hole/ membrane crack formation. The cell voltage of neighbouring cells exhibited an irregular instability, likely caused by the uneven reaction current density normally observed near a pin-hole [13] and the coupling between adjacent cells [31]. The proposed cause of this was localised flooding due to uneven pressure drops, leading to localised hotspots and weakening of the membrane.…”

Section: Experimental Set-upmentioning

confidence: 99%

“…However, as highlighted by Santis et al [31], current and therefore voltage heterogeneities in the cells of a PEMFC stack can affect adjacent cells due to the high electrical conductivity of the bipolar plates, with the failure of one cell often inducing changes in neighbouring cells. To understand the nature of pin-hole formation and the coupled behaviour of multiple cells together, investigations of full-scale stacks in real time are required, which is rarely reported in the literature.…”

Section: Introductionmentioning

confidence: 99%

Real-time monitoring of proton exchange membrane fuel cell stack failure

Parkes

Benedetti

et al. 2016

J Appl Electrochem

View full text Add to dashboard Cite

Uneven pressure drops in a 75-cell 9.5-kWe proton exchange membrane fuel cell stack with a U-shaped flow configuration have been shown to cause localised flooding. Condensed water then leads to localised cell heating, resulting in reduced membrane durability. Upon purging of the anode manifold, the resulting mechanical strain on the membrane can lead to the formation of a pin-hole/membrane crack and a rapid decrease in open circuit voltage due to gas crossover. This failure has the potential to cascade to neighbouring cells due to the bipolar plate coupling and the current density heterogeneities arising from the pin-hole/membrane crack. Reintroduction of hydrogen after failure results in cell voltage loss propagating from the pin-hole/membrane crack location due to reactant crossover from the anode to the cathode, given that the anode pressure is higher than the cathode pressure. Through these observations, it is recommended that purging is avoided when the onset of flooding is observed to prevent irreparable damage to the stack. Graphical AbstractKeywords Proton exchange membrane fuel cell Á Pin-hole Á Failure Á Flooding Á Purging Á Cell voltage monitoring

show abstract

Experimental investigation of coupling phenomena in polymer electrolyte fuel cell stacks

Cited by 39 publications

References 8 publications

Drops, slugs, and flooding in polymer electrolyte membrane fuel cells

Drops, slugs, and flooding in polymer electrolyte membrane fuel cells

Reduced dimensional computational models of polymer electrolyte membrane fuel cell stacks

Real-time monitoring of proton exchange membrane fuel cell stack failure

Contact Info

Product

Resources

About