Book/Dissertation / PhD Thesis FZJ-2019-05389

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Mechanische Eigenschaften von Polymer-Elektrolyt-Membran-Brennstoffzellen



2019
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag Jülich
ISBN: 978-3-95806-435-5

Jülich : Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag, Schriften des Forschungszentrums Jülich Reihe Energie & Umwelt / Energy & Environment 478, 177 pages () = Dissertation, RWTH Aachen University, 2019

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Abstract: The polymer electrolyte membrane (PEM) fuel cell is conventionally constructed of a plurality of thin layer components that are pressed against each other by end plates and clamping elements in order to ensure electrical contact amongst the layers and tightness of the cell’s construction. If the contact pressure is increased, the contact resistances of the layers decrease, and in turn the ohmic resistance of the cell decreases. In this case, however, the porosity of the gas diffusion layer is reduced, whereby the capacity of the active cell surface to be supplied with the reaction gases increasingly declines. As these two effects are in opposite directions, an optimum value for the contact pressure with respect to the performance of the fuel cell must result. In this work the optimum for the average contact pressure on the active surface is determined for three commonly used GDL types. For a GDL paper with MPL, this becomes 0.4 to 0.6 MPa (SGL 29BC), for a GDL paper without MPL, 0.6 to 1.7 MPa (Toray TGP H 060) and for a GDL felt with MPL, 0.6 to 2.7 MPa (Freudenberg H2315 C2). For the carbon felt and carbon paper materials with and without MPL, there are, therefore, clearly different performance optimizations. For a detailed understanding of the resulting pressure window, the fiber structures of the GDL materials are examined by means of mechanical material testing, scanning electron microscopy and computed tomography images. It can be stated that the processes responsible for the irreversible power loss at higher contact pressures in the case of GDL paper with MPL (SGL) are due to the irreversible changes in thickness and the concomitant drop in porosity and permeability. In the case of GDL paper without MPL (Toray), fiber and binder material fractures are observed at the corresponding contact pressures, the fragments of which reduce the pores and thus lead to a loss of performance of the cell. The GDL felt with MPL (Freudenberg) suffers no such structural damage and shows no performance losses, even at higher contact pressures of up to 2.7 MPa. For the transferability of the optimal contact pressure window to other graphitic flowfields, the locally actual pressures under the channel and rib are determined, as well as the general transferability to the stack scale and stronglydeviating flowfield geometries such as stamped metallic flowfields are tested


Note: Dissertation, RWTH Aachen University, 2019

Contributing Institute(s):
  1. Technoökonomische Systemanalyse (IEK-3)
Research Program(s):
  1. 135 - Fuel Cells (POF3-135) (POF3-135)

Appears in the scientific report 2019
Database coverage:
Creative Commons Attribution CC BY 4.0 ; OpenAccess
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Document types > Theses > Ph.D. Theses
Institute Collections > IEK > IEK-3
Document types > Books > Books
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 Record created 2019-11-08, last modified 2022-09-30