Towards uniformly distributed heat, mass and charge: A flow field design study for high pressure and high current density operation of PEM electrolysis cells

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Abstract

In this work, a state-of-the-art, full-scale, Proton Exchange Membrane

(PEM) electrolysis cell model is presented. The developed three-dimensional

(3D) model accounts for compressible, two-phase flow including species,

heat and charge transport in the anode and membrane. By incorporating

electrochemistry as well as detailed heat and two-phase flow transport

phenomena, the model is capable of studying cells at full-scale and

for high current densities with high accuracy. To enable the modeling

of thin catalyst layers (CL) for high current density operation in

a 3D framework, the CL is modeled as an interfacial boundary.


The necessary electrochemical parameters are obtained by fitting polarization

curves of a two-dimensional version of the devised model to experimental

measurements from a small cell. It is found that the obtained parameters

are in agreement with literature values and that the fitted model

is able to capture the performance for temperatures from 323 to 353 K

and for current densities up to 5 A cm-2.

Furthermore, it is identified that for high current density operation,

three types of overpotential losses are nearly equally dominant: the

anode kinetics, the PEM ohmic resistance and the non-membrane ohmic

resistance due to poor electrical contact between layers and current

constrictions in the CL.


The developed 3D model is applied to three different circular, interdigitated

anode flow fields aimed a high pressure and high current density operation.

When operating the cell at a cathode pressure of 100 bar, a current

density of 5 A cm-2 and stoichiometric constant of 350, it is

found that the cell potential shows little dependence on the applied

flow field. However, large in-plane variations can occur that may

impact lifetime significantly. Particularly for the temperature field,

an in-plane difference of up to 20.2 K relative to the intended cell

temperature is found in the worst case. For all three cases, the occurrence

of hot spots is linked to the maldistribution of two-phase flow and

current density. Out of the studied cases, it was found that equal

land width between the channels gives the best distribution of charge,

mass and heat. 

Luk

Detaljer

In this work, a state-of-the-art, full-scale, Proton Exchange Membrane

(PEM) electrolysis cell model is presented. The developed three-dimensional

(3D) model accounts for compressible, two-phase flow including species,

heat and charge transport in the anode and membrane. By incorporating

electrochemistry as well as detailed heat and two-phase flow transport

phenomena, the model is capable of studying cells at full-scale and

for high current densities with high accuracy. To enable the modeling

of thin catalyst layers (CL) for high current density operation in

a 3D framework, the CL is modeled as an interfacial boundary.


The necessary electrochemical parameters are obtained by fitting polarization

curves of a two-dimensional version of the devised model to experimental

measurements from a small cell. It is found that the obtained parameters

are in agreement with literature values and that the fitted model

is able to capture the performance for temperatures from 323 to 353 K

and for current densities up to 5 A cm-2.

Furthermore, it is identified that for high current density operation,

three types of overpotential losses are nearly equally dominant: the

anode kinetics, the PEM ohmic resistance and the non-membrane ohmic

resistance due to poor electrical contact between layers and current

constrictions in the CL.


The developed 3D model is applied to three different circular, interdigitated

anode flow fields aimed a high pressure and high current density operation.

When operating the cell at a cathode pressure of 100 bar, a current

density of 5 A cm-2 and stoichiometric constant of 350, it is

found that the cell potential shows little dependence on the applied

flow field. However, large in-plane variations can occur that may

impact lifetime significantly. Particularly for the temperature field,

an in-plane difference of up to 20.2 K relative to the intended cell

temperature is found in the worst case. For all three cases, the occurrence

of hot spots is linked to the maldistribution of two-phase flow and

current density. Out of the studied cases, it was found that equal

land width between the channels gives the best distribution of charge,

mass and heat. 

OriginalsprogEngelsk
TidsskriftElectrochimica Acta
Volume/Bind293
Sider (fra-til)476-495
Antal sider20
ISSN0013-4686
DOI
StatusUdgivet - 10 jan. 2019
PublikationsartForskning
Peer reviewJa
ID: 287696109