Updated:
04.11.2009
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Fuel Cell Systems
Project Description
The Fuel Cell Systems Group is a collaborative effort of electrochemist and engineers. It was established in 2002 as part of the PSI Laboratory for Electrochemistry. Current research activities in the field Polymer Electrolyte Fuel Cells (PEFC) are carried out on the relevant levels of:
Sub-Cell Scale
Cell Scale
Stack and Systems Scales
The investigation of the limiting processes and heterogeneities on all the scales are of high interest for improving PEFC technology An interdisciplinary approach of combined development of modeling and experimental techniques is pursued to elucidate the relevant processes and characteristics and to improve the performance of PEFC technology.
Sub-Cell Scale top |
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| The current density distribution on all scales is of high interest for the optimization of cell structures with respect to power density, which is associated to performance and costs. On the sub-millimeter scale, the current density is inhomogeneous over flow field ribs and gas channels (see Figure 1). At high current densities and / or low oxygen fraction at the cathode, mass transport limitations cause a major part of the total losses. Novel methods are developed for characterization of the relevant parameters, such as local current density (Figure 1) and membrane resistance measurements on the sub-mm scale. |
Figure 1: Current density distribution as function of oxygen fraction in cathode gas on the channel and rib domain of flow field plates. |
| Mass transport is strongly influenced by structural properties of the gas distributor, i.e. the flow field geometry and the mass transport properties of the gas diffusion layer (GDL). Characterization by electrochemical and synchrotron based methods are developed. Figure 2 shows the anisotropy of the effective diffusivity of a standard gas diffusion material (Toray Graphite Paper) as function of the pressure induced porosity. |
Figure 2: Effective relative diffusivity of TGPH gas diffusion layer material. Measure with the conductivity/diffusivity analogy approach |
Development of a steady state and dynamic macro homogeneous model, to generalize the experimental findings is pursued. This includes the experimental determination of the relevant transport parameters in the porous gas diffusion layers (GDL), as well as the investigation of the structural mechanics. |
Figure 3: Oxygen concentration under limiting current conditions. Data obtained with true anisotropic effective diffusivity of the GDL under mechanical load. |
Cell Scale top
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| Electrochemical engineering aspects of PEFC stack development, e.g., water management and humidification, heat management, current distribution, cooling, freezing are addressed. On the cell scale the entire cell, heterogeneities along the gas channels are of prime interest. |
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In addition to established local characterization methods (i.e. current density), special techniques for in-situ characterization are developed, i.e. local gas analysis. Special fuel cell and sampling hardware is developed for these investigations (Figure 4). |
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| Experimental results are generalized with a cell scale model, based on the philosophy of a 1+1 dimensional spatial grid (see Figure 2). Goal of modelling effort is the application of these tools for the analysis and design of cells of technical relevance |
Figure 4: Top: Specialized cell hardware for measuring local properties. Bottom: Calculated (lines) and measured (symbols) current density distribution in cells with applied temperature gradient. Upper graph: falling temperature along air flow. Lower graph: Rising temperature along air flow. |
Stack and Systems Scale top
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| Electrochemical engineering aspects of PEFC stack development, e.g., water management and humidification, heat management, current distribution, cooling, freezing, sealing, and investigation, adaptation and optimisation of membrane/electrode assemblies are addressed. In collaboration with Swiss Federal Institute of Technology in Zürich (ETHZ) several 8 kW stacks (see Figure 5) have been developed and built. |
Figure 5: 125-cell 8 kW PEFC stack, developed in collaboration with ETH Zürich.
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| Together with partners from industry and academia the fuel cell systems for the fuel cell based powertrains of the HY.POWER and HY.LIGHT cars were developed and built and. |
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| A new stack generation for mobile systems in the kW-range with innovative features such as internal gas humidification has been developed and characterized in collaboration with ETHZ and industrial partners. The applicability was demonstraded in the portable system PowerPac. |
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| The same stack generation was also used for PAC-Car II developed by ETHZ, holding the current record of minimum consumption at the shell eco-marathon. Using hydrogen as the fuel, PAC-Car II covers a distance of 5385km with the energy contained in 1L of gasoline. |
Figure 6: Top: HY.LIGHT car, developed in collaboration with Conception et Développment Michelin (CDM). Middle: Portable PE-Fuel Cell System “PowerPac”. 1 kW-System based on an internally humidified stack. Bottom: PAC-Car II (picture © ETH Zürich). |
Recent Publications
Research Team
- Felix N. Büchi
- Jérôme Bernard
- Jens Eller
- Thomas Gloor
- Marcel Hofer
- Stefan Kreitmeier
- Gabriel Schuler
- Maurizio Zaglio
For telephone and e-mail addresses see the PSI Directory Services page
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Contact Point
If you have a problem for which our expertise could be
of use, we would like to become YOUR partner - please do not hesitate
to contact us!
Dr. Felix N. Büchi
Laboratory for Electrochemistry
Paul Scherrer Institut
CH-5232 Villigen PSI
SWITZERLAND |
phone +41 56 310 24 11
fax +41 56 310 44 15
e-mail see PSI Phone Book |
or any other member of the research team.
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