Journal of Power Sources 155 (2006) 60–65
Short communication
Development of a stack having an optimized flow field
structure with low cross transport effects
J. Scholta
∗
,F.H
¨
aussler, W. Zhang, L. K
¨
uppers, L. J
¨
orissen, W. Lehnert
Zentrum f¨ur Sonnenenergie- und Wasserstoff-Forschung, GB 3: Elektrochemische Energiespeicherung
und -wandlung, Helmholtzstr. 8, D-89081 Ulm, Germany
Received 4 February 2004; accepted 9 May 2005
Available online 1 September 2005
Abstract
PEM fuel cells when operated on hydrogen from renewable sources are viewedas one of the most environmentally friendly energy conversion
systems due to their high electrical efficiency. However, this advantage is depending on the overall system design, which is largely determined
by the allowable operating conditions of the fuel cell stack itself. Besides the active materials, design and shape of the gas distribution zone
have a significant influence on stack operation. In order to optimize overall system performance, a fuel cell stack with improved flow field
design and performance was developed. An investigation on channel geometries led to a serpentine flow field with a moderate degree of
parallelization and ribs with variable width to reduce cross transport effects. The resulting flow field subsequently has been modified slightly
to allow a high volume production process. Summarizing, power as well as the degrees of H
2
and air utilization could be enhanced leading
to a power density enhancement. Furthermore, weight reduction of end plates nearly by half using an improved end plate design led to an
overall improved stack design.
© 2005 Elsevier B.V. All rights reserved.
Keywords: Fuel cell; PEMFC; Flow field design; Rib and channel geometry; Cross transport effects
1. Introduction
ZSW is developing PEM fuel cell stacks for use in portable
power generation and stationary applications since 1995.
Stacks with 50 cells having an active area of 100 cm
2
per
cell resulting in a total power output up to 1.4 kW have been
built and operated successfully. A power density of up to
0.3Wcm
−2
at an averaged single cell voltage of 0.6 V has
been obtained, however, at comparatively low gas utiliza-
tion. From a system point of view, it is evident, that hydrogen
and air utilization is of great influence to the overall sys-
tem efficiency. In this work, the influence of flow direction,
flow field geometry and channel geometries on the stack per-
formance have been studied, and experimental results on
∗
Corresponding author. Tel.: +49 731 9530 206; fax: +49 731 9530 666.
E-mail address: joachim.scholta@zsw-bw.de (J. Scholta).
URL: http://www.zsw-bw.de.
the effects of relative flow direction and flow field geom-
etry will be reported. Additional studies on the influence
of channel geometries are in progress and will be reported
elsewhere [1].
2. Experimental procedures
Starting from ZSWs standard configuration (internal man-
ifold, cross flow), an experimental investigation on the influ-
ence of media flow directions and channel geometry has been
carried out. A total of 10 different five-cell short stacks with
varying width and depth of the flow channels and width of
the ribs separating the channels were built and tested. Com-
mercially available membrane electrode assemblies (MEA)
and gas diffusion layers (GDL) were used. Stacks made from
the previous standard design (cross flow) were tested as a
reference. The experimental work was accompanied by CFD
modeling using FLUENT
TM
software.
0378-7753/$ – see front matter © 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.jpowsour.2005.05.101