H2Tech - Q4 2021 - 21

FUTURE OF HYDROGEN ENERGY
may deteriorate the performance of the
active layer over time.
Modeling and simulations are not
only useful for exploring new ideas.
Once a good design has been innovated,
mathematical models can be used to
further optimize design and operational
parameters. This development is evolutionary
and can be made almost automatic
by gathering data from operation.
The fuel cell unit cell and stack. Each
microscopic part of a fuel cell is affected
by the configuration of each cell and of
the entire fuel cell stack. This implies
that the microscopic details cannot be
studied in isolation. They have to couple
to the macroscopic factors that may
impact a cell. The simulation shown in
FIG. 4 treats an H2
channel and an oxygen
channel in a fuel cell unit cell, with
the electrodes and the membrane in between,
as shown in FIG. 5.
Each unit may be part of a stack connected
to an external circuit, as shown in
FIG. 6. The units may be equipped with
straight parallel channels (FIG. 6) or serpentine
channels (FIG. 7). Modern fuel
cells, like in the Toyota Mirai,7
may also
have a more complex structure for the O2
(air) gas feed. Here, a louver-like structure
allows for water to flow down with
gravity, away from the cathode, while
oxygen can flow upward.
In this way, the transport of liquid
electrode is enhanced,
and may also cause flooding. In
modeling and simulations can also be
used to determine the state and remaining
service life of a fuel cell system.3
4
water in the O2
which also enhances the transport of O2
to the active layer. Liquid water in the
porous electrode hinders the transport
of O2
addition, the use of a thinner membrane
allows for back diffusion of water from
the cathode to the anode, which also
eliminates the need for humidifying the
anode gas and lowers the risk of flooding.
Toyota, with this design, has considerably
enhanced the performance
and simplified the design of its fuel cell.7
FIG. 8 shows a schematic drawing of
what this louver structure may look like.
High-fidelity models can be coupled
and incorporated in models of a fuel cell
unit cell, a stack and an entire system,
including the electric drivetrain of the
vehicle (the load in FIG. 6). This requires
using fitted lumped models and reduced
models that are automatically updated
using detailed models when a new range
of operation is encountered. In this way,
Takeaway. The development of fuel
cells and the design of the active layer
will continue to lead to lower platinum
loads, longer service life and increased
power density. To a great extent, this will
be due to the understanding, innovation
and optimization tools offered by modeling
and simulations. These tools will
also allow for an optimal combination of
fuel cells, batteries and supercapacitors
to deliver energy and power density at a
low cost and with maximum service life.
Modeling and simulations will continue
to be important in the work of reducing
greenhouse gas emissions and other pollutants
from cars, buses and trucks.
LITERATURE CITED
1 Bethoux, O., " H2
fuel cell road vehicles and
their infrastructure: An option towards an
environmentally friendly energy transition, " Energies
2020, online: https://doi.org/10.3390/en13226132
2
Strahl, S., A. Husar and A. Franco, " Electrode
structure effects on the performance of opencathode
proton exchange membrane fuel cells:
A multiscale modeling approach, " International
Journal of Hydrogen Energy, 2014.
3 Sorrentino, A., K. Sundmacher and T. Vidakovic5
Koch,
" Polymer electrolyte fuel cell degradation
mechanisms and their diagnosis by frequency
response analysis methods: A review, " Energies 2020,
online: https://doi.org/10.3390/en13215825
Wiezell, K., P. Gode and G. Lindbergh, " Steady-state
and EIS investigations of hydrogen electrodes and
membranes in polymer electrolyte fuel cells, "
Journal of the Electrochemical Society, 2006.
Wiezell, K., " Modeling and experimental
investigation of the dynamics in polymer electrolyte
fuel cells, " KTH Royal Institute of Technology,
licensed thesis, Stockholm, Sweden, 2009.
6
Sandström, R., " Innovations in nanomaterials for
proton exchange membrane fuel cells, " doctoral
thesis, Department of Physics, Umeå 2019.
7
Yoshida, T. and K. Kojima, " Toyota MIRAI fuel
cell vehicle and progress toward a future hydrogen
society, " The Electrochemical Society Interface,
Vol. 24, No. 2, 2015.
ED FONTES is the Chief Technology
Officer at COMSOL. He has
been with COMSOL since 1999,
and previously served as the Lead
Developer for the CFD, heat transfer
and chemical engineering products.
Dr. Fontes received his PhD in
chemical engineering from the Royal Institute of
Technology, Stockholm.
HENRIK EKSTRÖM is the Technology
Manager for electrochemistry at
COMSOL. Prior to joining COMSOL
in 2010, Dr. Ekström worked at
various fuel cell startup firms in
Sweden. He received his PhD in
chemical engineering from the
Royal Institute of Technology, Stockholm.
H2Tech | Q4 2021 21
FIG. 8. A louver-like structure allows for water to flow down and O2
in the electrode.7
(air) to flow up. In this way,
the transport of liquid water away from the cathode is enhanced and does not obstruct the
transport of O2
SPECIAL FOCUS
https://www.doi.org/10.3390/en13215825 https://www.doi.org/10.3390/en13226132
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