Matching of critical parameters in a small non-pressurized non-humidified PEMFC stack

Chan, Siew Hwa; Xia, Zetao; Wei, Zhenxing

doi:10.1016/j.jpowsour.2005.10.009

Cited by 8 publications

(7 citation statements)

References 15 publications

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“…For reactant flows arranged in a coflow manner, the gas flow rates were kept at different stoichiometric values (1.15 times for H2 and 2.5 times for air 2 at IACM current density). Chan et al [7] combined the relationship between conductivity and water loading, and the relationship between relative humidity which shows that the higher the relative humidity, the higher the conductivity, especially when the relative humidity is over 605. In this experiment, to achieve the good conductivity, the humidity is set to 1000, and the cell/stack repeatedly run under the full load before the voltage response is measured; thereby the membrane can be humidified sufficiently.…”

Section: Methodsmentioning

confidence: 99%

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The Electrical Dynamic Response Study of PEMFC as a Backup Power Supply

Jia

Wang

Cham

et al. 2007

2007 IEEE International Conference on Control and Automation

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The use of fuel cell technology as a backup power source for the uninterruptible power supply (UPS) requires quick response to sudden load change. However, slow dynamic behavior of a PEM fuel cell, compared to the typical power conditioner and load, limits the fuel cell rapid transient response to load change. To increase the fuel cell response to load change, the energy storage such as battery, micro turbine, photovoltaic and super-capacitors are conventionally installed in the system thus increasing in its size and cost. In this work, the PEM fuel cell transient behaviors in the cool-start, hot-start and load change were investigated by using in-house running control software and high precise oscilloscope. The effects of fuel cell structure (area of flow field, cell number and materials used in MEA) and operation conditions (pressure, temperature etc.) were also studied. The electrical response results from experimental curves indicate that the transient behavior of fuel cell stack is highly impacted by the fuel cell structure, operating conditions and the strategy of gas input into the fuel cell. The better understanding of the electrical response of PEM fuel cell would be helpful to the design of a fuel cell and its system with high efficiency and compact structure.

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Section: Methodsmentioning

confidence: 99%

“…When it is in inverse polarity, the reaction at the anode is, 2H20 -4H+ + 4e-+ 02 at cathode, the reaction is, 4H 1 +4e--2H2 (6)(7) 1159 ill-f…”

mentioning

confidence: 99%

The Electrical Dynamic Response Study of PEMFC as a Backup Power Supply

Jia

Wang

Cham

et al. 2007

2007 IEEE International Conference on Control and Automation

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“…With the objective of maximized energy efficiency, Chan et al 10 established the relationships between the membrane conductivity and the water loading, the water loading and the relative humidity, and the relative humidity and the air stoichiometry number at different isothermal cell temperature. Note that the model assumed that the adsorption and capillary condensation of water vapor in porous electrodes were not significant.…”

mentioning

confidence: 99%

“…In between the detailed stack design [4][5][6] with the help of sophisticated mathematical models [7][8][9] and the tedious experimental trialand-error approach involving conceptual design, there seems to be lack of knowledge that would provide useful guidelines for the prototype design through matching of critical parameters associated with the performance and operating requirements of the fuel cell. With the objective of maximized energy efficiency, Chan et al 10 established the relationships between the membrane conductivity and the water loading, the water loading and the relative humidity, and the relative humidity and the air stoichiometry number at different isothermal cell temperature. Note that the model assumed that the adsorption and capillary condensation of water vapor in porous electrodes were not significant.…”

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confidence: 99%

Guidelines for Stable Operation of a Polymer Electrolyte Fuel Cell with Self-Humidifying Membrane Electrolyte Assembly

Chan

Han

2007

J. Electrochem. Soc.

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The desired performance of a polymer electrolyte fuel cell is always hindered by mismatching of operating conditions ͑such as temperature, flow rates of fuel and oxidant, level of humidification of reactants, etc.͒ with parameters associated with the cell performance ͑such as electrolyte conductivity, net back diffusion of water behavior in the membrane electrolyte assembly, etc.͒. This paper presents some design guidelines for polymer electrolyte fuel cells by establishing relationships among critical parameters of the fuel cell and is particularly useful for the developmental stage of mini/microfuel cells operating under nonpressurized condition and without external humidification of fuel.Polymer electrolyte fuel cells or widely named as proton exchange membrane fuel cells ͑PEMFCs͒ have made tremendous strides in the past few years. Research and development in fuel cells, in particular for micro/mini power sources, focus on miniaturization of the cell component and its component microstructure by employing micro/nanomachining technologies. In addition to researching on cell stacking methodology, flow patterning design based on simulation and combined conceptual design and trial-and-error approaches are also popular. Nguyen and Chan 1 reviewed the recent progress of the development of micromachined membrane-based fuel cells for both H 2 -fed and direct methanol-fed fuel cells. The review focused on the choice of materials and the design consideration of the components in the miniature fuel cell. Performances of the microfuel cells with different designs and under different operating settings were also compared.As is known, to achieve a stable and high-performance PEMFC there must be sufficient water in the polymer membrane, because the proton conductivity is directly related to the water content in the membrane. However, the amount of water should not be too excessive causing cathode flooding, thus blocking the pores in the electrodes for air diffusion. A good water balance is thus an important consideration in PEMFC. The dehydration of membrane comes from two possible sources: electro-osmotic drag pulling water molecules from the anode to the cathode during the migration of protons, 2,3 and loss of water to unsaturated flow streams by ͑force͒ convection. The first source is an inherent problem which can be worse under high overpotential in a poor design PEMFC. The understanding of the second source is important for self-humidifying fuel cell design, which is the case for micro/minifuel cell where introducing water by means of external humidification of reactants is impractical. Thus, water which forms in the cathode should properly be managed so as to keep the membrane at the correct level of hydration but not too excessively causing electrode flooding. Though water balance can be determined by computational fluid dynamics ͑CFD͒ modeling approach, most models developed for such a purpose are over simplified due to the extremely complicated electrochemical processes and transport phenomena involved in the porous...

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“…possibility of the self-humidifying operation in PEFC is developed based on the work reported byChan et al [2006] andYu [2000]. The suitable range of operating temperatures and air stoichiometric number under different condition can…”

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confidence: 99%

Investigation of performance and microstructure of membrane-electrode-assembly in PEMFC

Han¹

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In this study, a carbon-filled gas diffusion layer (CFGDL), and a novel selfhumidifying membrane electrode assembly (MEA) for proton exchange membrane fuel cell (PEMFC) were developed for improvement of the performance of PEMFC. The studies are included in detail as follows: 1. A new structural design of gas diffusion layer (GDL)-CFGDL is made of electrical conductive macro-porous carbon paper filled with a mixture of conductive carbon powder and hydrophobic polymer (PTFE). The systematic study on the properties of CFGDLs and their electrodes with various physical analysis techniques and electrochemical characterizations were carried out in comparison with conventional one-layer GDL, dual-layer GDL, and gained an insight into the relationship between the electrode performance and GDL structure. 2. The effects of material composition in CFGDL on the microstructure and performance of CFGDL were studied. The experimental results showed that the carbon loading in the CFGDL plays a critical role in the electrode performance and Pt utilization, but the PTFE content in the CFGDL has lesser influence. 3. The effect of PTFE content on the mass transport in the CFGDL was studied. It was found that the PTFE content in CFGDL significantly affected the contact angle (hydrophobic property) and water uptake (immobile liquid saturation) of CFGDL. The analysis by a theoretical model developed for cathode flooding, in which the water saturation is incorporated, shows that the mass transport limitation of fuel cells at high current density is attributed to the water flooding when using CFGDL with a lower PTFE content.

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Matching of critical parameters in a small non-pressurized non-humidified PEMFC stack

Cited by 8 publications

References 15 publications

The Electrical Dynamic Response Study of PEMFC as a Backup Power Supply

The Electrical Dynamic Response Study of PEMFC as a Backup Power Supply

Guidelines for Stable Operation of a Polymer Electrolyte Fuel Cell with Self-Humidifying Membrane Electrolyte Assembly

Investigation of performance and microstructure of membrane-electrode-assembly in PEMFC

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