This title appears in the Scientific Report :
2005
Please use the identifier:
http://hdl.handle.net/2128/545 in citations.
Entwicklung und Modellierung eines Polymerelektrolyt-Brennstoffzellenstapels der 5 kW Klasse
Entwicklung und Modellierung eines Polymerelektrolyt-Brennstoffzellenstapels der 5 kW Klasse
Polymer electrolyte fuel cells (PEFCs) require considerable optimization before they can compete with technologies already established on the market. The approaches described in this thesis contribute to the optimized design of PEFCs of the 5 kW class. The approaches concern the mutual interactions...
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Personal Name(s): | Wüster, Thorsten (Corresponding author) |
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Contributing Institute: |
Energieverfahrenstechnik; IWV-3 |
Imprint: |
Jülich
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag
2005
|
Physical Description: |
III, 204 S. |
Dissertation Note: |
RWTH Aachen, Diss., 2005 |
ISBN: |
3-89336-422-6 |
Document Type: |
Book Dissertation / PhD Thesis |
Research Program: |
Werkstoffsysteme für Kraftwerke Brennstoffzelle |
Series Title: |
Schriften des Forschungszentrums Jülich. Reihe Energietechnik / Energy Technology
46 |
Subject (ZB): | |
Link: |
OpenAccess |
Publikationsportal JuSER |
Polymer electrolyte fuel cells (PEFCs) require considerable optimization before they can compete with technologies already established on the market. The approaches described in this thesis contribute to the optimized design of PEFCs of the 5 kW class. The approaches concern the mutual interactions of individual components of the cell stack and place these interactions on a new model basis. They comprise, amongst other aspects, water and heat management, knowledge of the expected flow and current density distribution as well as the dependence of cell performance on the operating parameters. The generalized results can be transferred to the design and optimization of fuel cell stacks of different power classes. Experimental investigations of single cells and short stacks serve as the design basis for the 5 kW cell stack. Local changes in cell power caused by varying the operating parameters are determined by measuring the current density distribution. Two innovative measuring methods are used for this purpose. The first procedure is based on local in situ resistance measurements. The second non-invasive method of magnetic tomography permits conclusions to be drawn about the current density distribution inside the cell stack from measurements of magnetic flux density outside the cell stack. A novel, quasi-one-dimensional model is derived for characterizing PEFC performance in the form of voltage-current density curves. The application of the model shows that with decreasing operating pressure and rising current density the recommended maximum cathodic reactant conversion is shifted towards a higher oxygen stoichiometry coefficient. An effective rise in performance can be achieved by an enlarged catalyst surface area and increased catalyst activity. An analytical one-dimensional calculation approach determines that the media are uniformly distributed among the individual cells in a cell stack. This approach is generalized by combining the factors of influence into suitable dimensionless numbers. For any cell stack geometries, the uniformity of the media distribution is presented as a function of these numbers in a graphical and analytical form. Depending on the respective application, an operating pressure of 1.1 to 2.2 bar proves to be particularly suitable for operation of the 5 kW stack. A water-based cooling concept is selected for removing the reaction heat from the cell stack. The humidifier cells on the anode side are integrated into the fuel cell stack. The cooling water is fed into the humidifier cells after having been heated by flowing through the cell stack. The use of a capillary or hollow-fibre humidifier module is recommended in order to moisten the oxidant. Based on the results, a fuel cell stack consisting of 55 cells has been constructed and put into operation. An initial performance characterization shows that the envisaged power of 5 kW has been achieved. |