Understanding PEM fuel cell dynamics: The reversal curve

Arias, Ivonne Karina Peña; Trinke, Patrick; Hanke‐Rauschenbach, Richard; Sundmacher, Kai

doi:10.1016/j.ijhydene.2017.05.087

Cited by 26 publications

(12 citation statements)

References 42 publications

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“…The transient response is essential for both the hydrogen‐air and hydrogen‐oxygen PEMFCs, when used as mechanical power sources 7 . Unfavorable undershoot could occur during the loading process; dynamic voltage drops below the voltage at the steady state 8 . To study the dynamic performance of PEMFCs, extensive research has been carried out 9 …”

Section: Introductionmentioning

confidence: 99%

Load changing characteristics of the hydrogen‐air and hydrogen‐oxygen proton exchange membrane fuel cells

Huang

Xing

2021

Intl J of Energy Research

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Summary Load changing performance is significant for the application of proton exchange membrane fuel cells (PEMFCs). This paper compares experimental results of the hydrogen‐air and hydrogen‐oxygen PEMFC and analyzes their dynamic performance under various operating conditions. We use electrochemical impedance spectroscopy to investigate the intrinsic mechanism during load changing. Due to the higher oxygen concentration, the hydrogen‐oxygen PEMFC responds faster (within 1 second) and operates more steadily than the hydrogen‐air PEMFC (2‐20 seconds). The experimental results show that the total polarization resistance of the hydrogen‐air PEMFC and the Ohmic resistance of the hydrogen‐oxygen PEMFC decrease dramatically with the appropriately increased operating temperature. Whereas at over‐elevated operating temperature, the resistance value increases due to the dehydration of the membrane electrode assembly. Load changing performance can be improved by increasing operating pressure and relative humidity. Increased stoichiometry is beneficial for the hydrogen‐air PEMFC, while the opposite trend is observed for the hydrogen‐oxygen PEMFC. Novelty statement Comparison of experimental results of hydrogen‐air and hydrogen‐oxygen proton exchange membrane fuel cell (PEMFC), dynamic performance at start‐up, and load changing performance are studied. Two PEMFCs' performances are quite different at various operating conditions. Overall, H2/O2 PEMFCs response faster (1 second) and operate more steadily than H2‐air (2‐20 seconds). Ohmic, polarization, and mass transfer resistance values are measured and analyzed.

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Section: Introductionmentioning

confidence: 99%

Load changing characteristics of the hydrogen‐air and hydrogen‐oxygen proton exchange membrane fuel cells

Huang

Xing

2021

Intl J of Energy Research

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“…α ε α ρ α c p,α ∂T ∂t + u α • ∇T = ∇ • (k eff T ∇T ) + S T , [5] ∇ • (σ eff 1 ∇φ 1 ) = S e − , [6] ∇ • (σ eff 2 ∇φ 2 ) = S H + . [7] The first equation describes species transport in the microporous layers (MPLs), gas diffusion layers (GDLs), and CLs, where ε g is the porosity of the layer available for gas transport (ε g = ε(1 − s), with s the liquid saturation and ε the compressed layer porosity), c g is the total gas concentration, u g = − K eff g μg ∇ p g is the velocity of the gas phase, and c i , D eff i , and x i denote the concentration, the effective diffusivity, and the molar fraction of species i, respectively.…”

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confidence: 99%

Through-the-Membrane Transient Phenomena in PEM Fuel Cells: A Modeling Study

Goshtasbi

García-Salaberri

Chen

et al. 2019

J. Electrochem. Soc.

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This paper presents a 2D, fully coupled and comprehensive transient model that accounts for micro-structural features of various cell layers. The model benefits from state of the art sub-models for reaction kinetics and incorporates the polymer relaxation dynamics. Furthermore, a mixed wettability model is utilized to simulate the transient two phase conditions in the porous layers. The model is validated with transient experimental data under various conditions. A comprehensive simulation study is presented to investigate the impact of operating temperature and relative humidity on the transient response. The effects of cathode Pt loading and operation mode, i.e., current control versus voltage control, are also studied. The cell response is found to be dominated by water transport through its thickness. Additionally, it is found that reducing the Pt loading can influence the performance by changing the water balance in the cell, which has rarely been highlighted in the literature. In particular, at low temperature more water is transported toward the anode when the cathode Pt loading is reduced, since the resistance to water back diffusion is lowered with reduced thickness of the cathode catalyst layer. This trend is reversed at a higher temperature due to increased volumetric heat generation with reduced thickness. The model can help in understanding various transport phenomena and is expected to be useful for inspecting spatio-temporal temperature, potential, and species distributions across the cell's thickness and optimizing the cell design and choice of materials.

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“…18,19 Experimental and modeling analyzes have shown several effects that can be attributed in general to activation and diffusion processes or the humidification of the membrane. 13 As can be seen in the insets of Fig. 2 and Fig.…”

Section: Discussionmentioning

confidence: 73%

“…Load step analyzes for fuel cells revealed that an instantaneous characteristic is typical followed by a highly complex transient behavior due to activation, concentration and temperature effects. [11][12][13] Local analyses of the electrical and electrochemical response behavior have shown significant differences at the inlet and the outlet of a cell 14 and have indicated critical dynamic operation modes. 15 Additionally, unfeasible load steps are reported, which can be characterized by the reversal curve.…”

mentioning

confidence: 99%

Understanding Electrical Under- and Overshoots in Proton Exchange Membrane Water Electrolysis Cells

Immerz

Bensmann

Trinke

et al. 2019

J. Electrochem. Soc.

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Ability of dynamic operation seems to be an important feature of proton exchange membrane water electrolyzers (PEMWE) to become a relevant part of the future energy system. However, only few fundamental analyzes of the dynamic behavior on short time scales are available in the literature. Therefore, this contribution aims to give insights into the most fundamental transient behavior of a PEMWE cell by an experimental analysis on the laboratory scale and a model based description of the ongoing phenomena. Experimental voltage and current controlled load step are carried out and analyzed by methods adapted from fuel cell characterization. The experimental analysis revealed that load steps are a combination of an instantaneous characteristic followed by dynamics of higher order dependent on activation, mass transfer and temperature effects. Potentiostatic downward steps to very low cell voltages can lead to current density reversal phenomena with highly negative peak current densities. By means of a simple prototype model analysis, these reversal processes are analyzed and the consequences of the phenomena are estimated. The simulation results indicate that a reversal of the cell current density can be attributed to a change of capacitive rather than faradaic currents, meaning that internal electrolysis processes are not involved.

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Understanding PEM fuel cell dynamics: The reversal curve

Cited by 26 publications

References 42 publications

Load changing characteristics of the hydrogen‐air and hydrogen‐oxygen proton exchange membrane fuel cells

Load changing characteristics of the hydrogen‐air and hydrogen‐oxygen proton exchange membrane fuel cells

Through-the-Membrane Transient Phenomena in PEM Fuel Cells: A Modeling Study

Understanding Electrical Under- and Overshoots in Proton Exchange Membrane Water Electrolysis Cells

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