Article : [PAP602]

Titre : A. V. VIRKAR, J.-W. KIM, K. MEHTA, K.-Z. FUNG, Low temperature, high performance, planar solid oxide fuel cells and stacks, 14 pages.

Cité dans : [ART607]  S.K. MAZUMDER, K. ACHARYA, C.L. HAYNES, R. WILLIAMS, M.R. VON SPAKOVSKY, D.J. NELSON, D.F. RANCRUEL, J. HARTVIGSEN, R.S. GEMMEN, Solid-Oxide-Fuel-Cell Performance and Durability: Resolution of the Effects of Power-Conditioning Systems and Application Loa
Cité dans :[THESE133] B. BIDOGGIA, Etude et réalisation de nouveaux convertisseurs connectant plusieurs sources d'énergies renouvelables au réseau, These de doctorat, septembre 2005 - aout 2008.

Lien : private/FC6-5.pdf - 14 pages, 142 Ko.
Pages : 1 - 14
Lien : mailto:anil.virkar@m.cc.utah.edu
Phone : (801) 581-5396)
Lien : mailto:jkim@eng.utah.edu
Phone : (801) 581-3148)
Lien : mailto:kmehta@eng.utah.edu
Phone : (801) 581-3148)
Adresse : Department of Materials Science & Engineering, 304 EMRO - University of Utah - Salt lake City, UT 84112

Lien : mailto:kfung@materialsys.com
Phone : (801) 973-1199)
Adresse : Materials and Systems Research, Inc. - 1473 South Pioneer Road, Suite B - Salt lake city, UT 84104

Vers : Bibliographie

ABSTRACT :
Conversion of chemical energy of combustion of a fuel into electrical energy by fuel cells
continues to be an important thrust area of energy conversion technology. Among these, fuel
cells using either molten salt (MCFC) or solid oxide (SOFC) electrolytes are of particular
interest because operation at higher temperatures allows for the use of natural gas as a fuel.
High temperature fuel cells, however, are subject to materials-related problems such as
corrosion which increase with temperature. In addition, the Nernst potential also decreases
with increasing temperature. These two factors suggest that lowering of the operation
temperature is preferred. However, higher operating temperatures are desirable for internal
reforming as well as to minimize losses at electrolyte/electrode interfaces. Based on these
considerations, a temperature range between ~600 and ~800oC is considered optimum. The
focus of the present work has been on the development of solid oxide fuel cells made of thin
electrolyte films supported on a relatively thick anode.
Anode-supported single cells of approximately 3 cm diameter with anode thickness of ˜0.75
mm (750 µm), YSZ electrolyte thickness of ˜10 µm, and LSM + YSZ cathode thickness of ˜50
µm were fabricated. The cell fabrication procedure consists of depositing a thin film of YSZ by
dip-coating on a powder compact of a mixture of nickel oxide and YSZ. Densification was
achieved at a temperature below 1400°C. Single cells were tested between 650 and 800°C with
humidified hydrogen as the fuel and air as the oxidant. Maximum power density at 800°C was
» 1.8 W/cm2 (area specific resistance ~0.15 Wcm2) and that at 650°C was » 0.8 W/cm2 (area
specific resistance ~0.34 Wcm2). The area specific resistance of the cells obeyed Arrheniustype
behavior with an activation energy of 50 kJ/mol. The observed behavior is in accord with
the theoretical analysis of cell performance which takes into account transport of gaseous
species through the porous electrodes.
For stack testing, square-shaped cells of dimensions 5 cm x 5 cm x ~2-3 mm were made. Four
cell stacks with metallic interconnects were tested at 800°C. The interconnect was configured
from a commercial alloy foil of 5 mil thickness. The interconnect was subjected to surface
treatments to improve its performance. No glass seal was used. The edges of the metallic
interconnects serve as sealing gaskets. Manifolds were made of commercial alloys. The
manifolds are spring-loaded against the stack with electrically insulating gaskets. The absence
of a sealing glass allows one to disassemble the stack and reuse the same cells. Often, the same
cells were used more than ten times. Also, the presence of a large amount of nickel in the anode
renders the cells highly thermal shock-resistant. For example, a cell could be cooled from
800°C to room temperature within a few minutes. The typical repeat unit (anode-electrolytecathode-
interconnect) area specific resistance was measured to be ˜0.5 Wcm2. The cells used in
this preliminary work were of a thickness much greater than the most optimum. Current efforts
are directed towards lowering the thickness down to ˜1.5 mm.
from a commercial alloy foil of 5 mil thickness. The interconnect was subjected to surface
treatments to improve its performance. No glass seal was used. The edges of the metallic
interconnects serve as sealing gaskets. Manifolds were made of commercial alloys. The
manifolds are spring-loaded against the stack with electrically insulating gaskets. The absence
of a sealing glass allows one to disassemble the stack and reuse the same cells. Often, the same
cells were used more than ten times. Also, the presence of a large amount of nickel in the anode
renders the cells highly thermal shock-resistant. For example, a cell could be cooled from
800°C to room temperature within a few minutes. The typical repeat unit (anode-electrolytecathode-
interconnect) area specific resistance was measured to be ˜0.5 Wcm2. The cells used in
this preliminary work were of a thickness much greater than the most optimum. Current efforts
are directed towards lowering the thickness down to ˜1.5 mm.

Funded by Electric Power Research Institute (EPRI), Gas Research Institute (GRI), and the State of Utah.

Bibliographie

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