Effect of clamping pressure on ohmic resistance and compression of gas diffusion layers for polymer electrolyte fuel cells

Mason, Thomas J.; Millichamp, Jason; Neville, Tobias P.; El-Kharouf, Ahmad; Pollet, Bruno G.; Brett, Dan J. L.

doi:10.1016/j.jpowsour.2012.07.021

Cited by 110 publications

(58 citation statements)

References 19 publications

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“…• Develop a cyclic compression strategy to improve fuel cell stack performance by reducing ohmic losses [9]. • Place a mechanical stop to prevent over compression.…”

Section: Resultsmentioning

confidence: 99%

“…The literature presents a range of methodologies for investigating and ensuring the optimum compression ratio for fuel cells [8,9,22] and methods for identifying the uniformity and its effect on performance [10,11,15,16]. There are also some works which develop novel endplate structures and designs to improve uniformity [23,24].…”

Section: Literature Reviewmentioning

confidence: 99%

“…This series configuration is commonly referred to as a stack, which is compressed to optimise performance. The assessment and optimisation of fuel cell compression has been studied extensively in the literature [6][7][8][9][10][11][12][13][14][15][16] due to its importance in balancing ohmic losses and mass transport losses during operation. However, no literature has been found, to date, which identifies a process that produces repeatable fuel cell compression and lends itself to a low to medium volume (10's-1000's units per annum) manufacturing environment.…”

Section: Introductionmentioning

confidence: 99%

“…This has an effect of starving the fuel cell resulting in accelerated degradation as well as flooding, which further exacerbates these losses [17][18][19]. In addition, the compression of the GDL results in a phenomenon described as tenting [9] whereby the GDL deforms into the flow field channels. This reduces the volume available for transporting reactants and water within the channels of the flow field plate.…”

Section: Introductionmentioning

confidence: 99%

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Analysis of the compression characteristics of a PEM stack, development of an equivalent spring model and recommendations for compression process improvements

Ahmad

Harrison

Meredith

et al. 2015

IREC2015 the Sixth International Renewable Energy Congress

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Optimising the compression process during assembly improves the performance of fuel cells. Sufficient and uniform compression across the x,y and z axes ensures uniform current distribution contributing to stack longevity, minimisation of mechanical stresses and optimisation of the well-recognised compromise between mass transport and ohmic losses. In addition, the sealing media experience the necessary forces required to prevent the leakage of reactant gases and thus increase the efficiency of the system. This research paper evaluates the compression characteristics of a test version of a fuel cell compression rig, designed by Horizon Fuel Cell UK, to inform future assembly line design. A MATLAB code was used to assess the compression homogeneity presented on Fuji Prescale Low pressure films. A spring equivalent model is developed to approximate required compressive force for optimal performance. Optimisation of this model is expected to facilitate the development of a compression process which lends itself to the mass production of fuel cells. Recommendations for improving the current process include the use of electronically controlled cyclic compression and an increase in the number of compression pistons. The key finding of this study is a lack of compression symmetry which is associated with the alignment of the jig or component manufacturing and assembly tolerances.

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“…• Develop a cyclic compression strategy to improve fuel cell stack performance by reducing ohmic losses [9]. • Place a mechanical stop to prevent over compression.…”

Section: Resultsmentioning

confidence: 99%

Section: Literature Reviewmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Analysis of the compression characteristics of a PEM stack, development of an equivalent spring model and recommendations for compression process improvements

Ahmad

Harrison

Meredith

et al. 2015

IREC2015 the Sixth International Renewable Energy Congress

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“…Until recently, the main technique used to determine the GDL structure was scanning electron microscopy (SEM), frequently coupled with energy dispersive X-ray spectroscopy (EDS) analysis. SEM is useful in obtaining surface structural data, layer thickness, 'smoothness' of different interfaces, PTFE bonding, and fibre orientation, but fails to reveal the porosity and internal structure [5,6,[15][16][17][18][19][20][21][22]. Micro and nano X-ray computed tomography (CT) are non-destructive methods that can achieve sufficiently high resolution for the imaging of carbon fibres, which typically have diameters between 5 and 10 m, and they have been increasingly used to characterise GDLs [7,19,[23][24][25][26].…”

mentioning

confidence: 99%

Effect of gas diffusion layer properties on water distribution across air-cooled, open-cathode polymer electrolyte fuel cells: A combined ex-situ X-ray tomography and in-operando neutron imaging study

Meyer

Ashton

Boillat

et al. 2016

Electrochimica Acta

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2 Highlights First description of in-plane water distribution using neutron imaging in an aircooled, open-cathode fuel cell. High water content identified under cathode land area, whereas anode water content is relatively homogeneous. Water distribution in anode GDL directly linked to dispersion of PTFE. Anode GDL composition shown to affect water content and distribution in cathode. Combined X-ray computed tomography, SEM/EDS and TGA used to characterise GDL structure and composition. AbstractIn-situ diagnostic techniques provide a means of understanding the internal workings of fuel cells under normal operating conditions so that improved designs and operating regimes can be identified. Here, an approach is used which combines exsitu characterisation of two anode gas diffusion / microporous layers (GDL-A and GDL-B) with X-ray computed tomography and in-situ analysis using neutron imaging of operating fuel cells. The combination of TGA, SEM and X-ray computed tomography reveals that GDL-A has a thin microporous layer with 26 % PTFE covering a thick diffusion layer composed of 'spaghetti' shaped fibres. GDL-B is covered by two microporous media (29 % and 6.5 % PTFE) penetrating deep within the linear fibre network. The neutron imaging reveals two pathways for water management underneath the cooling channel, either diffusing through the cathode GDL to the active channels, or diffusing through the membrane and towards the 3 anode. Here, these two behaviours are directly affected by the anode gas diffusion PTFE content and porosity. KeywordsGas diffusion layer; air-cooled open-cathode; X-ray computed tomography; neutron imaging; water management. IntroductionPolymer electrolyte fuel cells (PEFC) fuelled with hydrogen are among the most promising energy conversion technologies for a broad range of applications, including portable, stationary and automotive power delivery. However, understanding the cell water management is crucial for performance optimisation.Flooding impedes reactant transport (water mainly concentrating at the cathode) and reduces the surface area of the catalyst, causing significant if not catastrophic decay in cell performance, and dehydration can lead to cracks and irreversible damage [1][2][3]. The gas diffusion layer (GDL) provides a pathway for electron transport, ensures even reactant delivery and helps water management within each cell. The water balance between flooding and membrane dehydration is a function of the GDL's structure, porosity and PTFE (hydrophobic) content. Here, two commercial GDLs with microporous layers are characterised ex-situ by capturing the design and structure via X-ray computed tomography (CT), along with its polytetrafluoroethylene (PTFE) / carbon distribution via SEM/EDS analysis and thermogravimetric analysis (TGA); in-situ 'visualisation' of the water distribution in the in-plane orientation was performed using neutron radiography. These techniques can be correlated with one another to gain new insights into the water management role of the GDL in fuel c...

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In Situ and Operando Characterization of Proton Exchange Membrane Fuel Cells

2019

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For proton-exchange-membrane fuel cells (PEMFCs) to become a mainstream energy source, significant improvements in their performance, durability, and efficiency are necessary. To improve their durability, there must be a solid understanding of how the structural and electrochemical processes are affected during operation to propose mitigation strategies. To this aim, in situ and operando characterization techniques locally identify structural and electrochemical processes, which cannot be captured using conventional techniques. Nevertheless, linking these properties in the same geometric area has been challenging due to its inherent limitations, such as sample size and imaging resolution. This has created a knowledge gap in structure-to-electrochemical performance relationships as operation and degradation unevenly affect different areas of the cell.

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Effect of clamping pressure on ohmic resistance and compression of gas diffusion layers for polymer electrolyte fuel cells

Cited by 110 publications

References 19 publications

Analysis of the compression characteristics of a PEM stack, development of an equivalent spring model and recommendations for compression process improvements

Analysis of the compression characteristics of a PEM stack, development of an equivalent spring model and recommendations for compression process improvements

Effect of gas diffusion layer properties on water distribution across air-cooled, open-cathode polymer electrolyte fuel cells: A combined ex-situ X-ray tomography and in-operando neutron imaging study

In Situ and Operando Characterization of Proton Exchange Membrane Fuel Cells

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