A Review on Graphical Methods for Modeling a Proton Exchange Membrane Fuel Cell

Fuel cell systems represent a promising alternative energy converter. In the past years, researches have been conducted for their modeling, control, and diagnosis. The model should accurately reproduce the behavior without being too complex. Due to the highly multiphysical interactions and coupling within the fuel cell, using a graphical representation for developing this model seems well suited. This paper presents a review of recent literature on graphical representation of proton exchange membrane fuel cell (PEMFC). Three main graphical representations are discussed: bond graph (BG), EMR, and equivalent electrical circuit. Their fields of application will be shown as well.

Characterization of Flow Within a Fuel Cell Manifold Subject to Asymmetric Inlet Conditions

Achievement of flow uniformity among cells of a fuel cell stack continues to be an issue in fuel cell design and can affect performance and longevity. While many studies have sought to examine the effects of manifold and cell geometries on stack pressure drops and current density, few have provided detailed mapping of the manifold flowfield or examined the effect of reactant supply pipe bends on this flow, as these bends can introduce flow asymmetries within the pipe downstream of the bend. A simplified scaled up model of a proton exchange membrane (PEM) fuel cell was fitted with different inlet flow configurations, including straight piping and piping containing a 90 deg bend and 180 deg bend prior to entering the manifold. Particle image velocimetry (PIV) was used to obtain mean and fluctuating velocity statistics within the manifold and in individual cells. These distributions were compared with previous results using a partially developed square inlet profile, as well as available experimental and computational data in the literature. The presence of pipe bends resulted in highly skewed flow within the manifold, which also affected the flow distribution among individual cells.

Depositing Catalyst Layers in Polymer Electrolyte Membrane Fuel Cells: A Review

Fuel cell technology continues to advance and offers to be a potentially promising solution to many energy needs. Of particular interest are manufacturing techniques to improve performance and decrease overall cost. For catalyst deposition on the membrane electrode assembly (MEA), there are a number of techniques that have been used in the past decades. This paper aims to review many of these main techniques that have been published to show the wide variety of catalyst deposition methods.

Experimental and Computational Evaluation of Performance and Water Management Characteristics of a Bio-Inspired Proton Exchange Membrane Fuel Cell

A bio-inspired proton exchange membrane (PEM) fuel cell with a flow field that mimics a leaf pattern is experimentally and computationally evaluated. Experiments are conducted using a transparent assembly for direct visualization of liquid water within the microchannels. Polarization and power curves are also obtained while advanced simulations are performed to predict distributions of pressure, velocity, and concentrations. The same measurements and computations are also performed for a single serpentine fuel cell. The results establish the superior water management and performance characteristics of the bio-inspired fuel cell in comparison to a conventional one. They also help elucidate the underlying transport mechanisms, validate the computational models, and guide the optimization of bio-inspired fuel cells.

Hybrid Direct Carbon Fuel Cell Performance With Anode Current Collector Material

The influence of the current collector on the performance of a hybrid direct carbon fuel cell (HDCFC), consisting of solid oxide fuel cell (SOFC) with a molten carbonate–carbon slurry in contact with the anode, has been investigated using current–voltage curves. Four different anode current collectors were studied: Au, Ni, Ag, and Pt. It was shown that the performance of the direct carbon fuel cell (DCFC) is dependent on the current collector materials, Ni and Pt giving the best performance, due to their catalytic activity. Gold is suggested to be the best material as an inert current collector, due to its low catalytic activity.

Interface Reactions Between Sealing Glass and Metal Interconnect Under Static and Dynamic Heat Treatment Conditions

Chemical compatibility of sealing glass with metal interconnects is a critical issue for planar solid oxide fuel cell (SOFC). In this paper, interface reactions between a sealing glass and a ferritic metal interconnect (SS410) are tested under three different heat treatment conditions: sealing (static), aging (static), and thermal cycling (dynamic). The results show that the BaCrO4 crystals with two different morphology (round-shaped and needle-shaped) form both at the three-phase boundary (where air, glass, and SS410 meet) and on the surface of the sealing glass under the three conditions. Round-shaped BaCrO4 crystals form with low O2 concentration and short reaction time. Needle-shaped BaCrO4 crystals form with high O2 concentration and long reaction time. For the thermal cycling condition, the BaCrO4 formed at early stages causes the delamination of the sealing interface. Then, O2 diffuses into the interior interface along the delamination path, which results in the formation of BaCrO4 at the interior interface. The delamination-enhanced BaCrO4 formation during thermal cycling will lead to crack along the sealing interface, causing the striking increase of leak rates.

Development and Validation of a Uniaxial Nonlinear Viscoelastic Viscoplastic Stress Model for a Fuel Cell Membrane

Proton exchange membranes (PEMs) in operating fuel cells are subjected to varying thermal and hygral loads while under mechanical constraint imposed within the compressed stack. Swelling during hygrothermal cycles can result in residual in-plane tensile stresses in the membrane and lead to mechanical degradation or failure through thinning or pinhole development. Numerical models can predict the stresses resulting from applied loads based on material characteristics, thus aiding in the development of more durable membrane materials. In this work, a nonlinear viscoelastic stress model based on the Schapery constitutive formulation is used with a viscoplastic term to describe the response of a novel membrane material comprised of a blend of perfluorocyclobutane (PFCB) ionomer and poly(vinylidene fluoride) (PVDF). Uniaxial creep and recovery experiments characterize the time-dependent linear viscoelastic compliance and the fitting parameters for the nonlinear viscoelastic viscoplastic model. The stress model is implemented in a commercial finite element code, abaqus®, to predict the response of a membrane subjected to mechanical loads. The stress model is validated by comparing model predictions to the experimental responses of membranes subjected to multiple-step creep, stress relaxation, and force ramp loads in uniaxial tension.

The Importance of Ion Selectivity of Perfluorinated Sulfonic Acid Membrane for the Performance of Proton Exchange Membrane Fuel Cells

Nafion 212 membrane was subjected to swelling–dehydration (SD) cycles, as a relevant operation condition for direct methanol fuel cells (DMFCs). The major degradation mechanism due to the treatment was found to be sulfonic group contamination with trace ion, rather than formation of sulfonic anhydride, which is a well-known degradation mechanism for Nafion® membranes under hydrothermal (HT) aging condition. The consequences of the degradation include decreasing water content, thickness, and surface fluoride and increasing resistance, dry weight, and a changed surface morphology. Ion selectivity of the sulfonic group was studied toward different fuel cell relevant conditions. It turned out that the sulfonic groups have much higher selectivity toward cations rather than neighbor sulfonic groups. Trace impurities in the liquid methanol feed in DMFC may therefore represent an important contamination source.

Synthesis and Characterization of Polyion Complex Membranes Made of Aminated Polyetherimide and Sulfonated Polyethersulfone for Fuel Cell Applications

Acid–base blends of sulfonated polyethersulfone (SPES) with pristine and aminated polyetherimide (APEI) are synthesized. Three blends polyethersulfone (PES)/polyetherimide (PEI), SPES/PEI, and SPES/APEI are prepared and characterized to evaluate their structural, morphological, mechanical, and other properties. Ion exchange capacity (IEC) of SPES/APEI and SPES/PEI blend membranes was determined to be 3.0 and 2.7 meq g−1, which is a substantial improvement over the 1.0 meq g−1 exhibited by unmodified PES/PEI blend. The proton conductivity of 0.093 S cm−1 displayed by SPES/APEI blend is found to be comparable to that of commercial Nafion membrane (0.056 S cm−1) and far superior to conductivities of 0.091 and 0.082 S cm−1 shown by SPES/PEI and PES/PEI blends, respectively. Further, water sorption observed in case of SPES/APEI and SPES/PEI blends was in the range 17–18% over a soaking time period of 12 hrs, which is ideal for proton conduction accompanied by low-membrane swelling. The methanol permeabilities of SPES/APEI and SPES/PEI blends are found to be 2.5 × 10−7 and 3.47 × 10−7 cm2 s−1, respectively. Compared to unmodified PES/PEI blend which revealed a methanol sorption of 12.3%, the modified blends SPES/PEI (9.6%) and SPES/APEI (7.5%) exhibited much lower methanol uptake over a sorption time of 12 hrs, indicating their capacity for low fuel bypass. The results demonstrate the promising potential of polymer blends made by combining a sulfonated polymer with an aminated polymer, such as SPES/APEI for fuel cell (FC) applications.