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Development of a solid oxide fuel cell (SOFC)

Objective

Development of a flat plate 1kW solid oxide fuel cell with a metal separator plate. Two flat plate SOFC concepts will be developed by Siemens and ECN respectively. After comparative tests one concept will be selected for the construction of the 100 W and 1 kW units.
Starting from the results of a foregoing CEC-project where fundamental research and development activities have been carried out, the Siemens Solid Oxide Fuel Cell (SOFC) reactor concept was realized for the 1 kW SOFC class. The characteristic point of this fuel cell reactor type is the multifunctional metallic bi-polar plate serving as separator between fuel- and oxidant gas, as electrical link between cells connected in series and as support of the thin ceramic composite of positive electrode/electrolyte/negative electrode (PEN). The stack representing the 1 kW type was built up by 9 bipolar plates with 4 PENs of the dimensions 5 x 5 cm{2} on each plate and an additional PEN layer on the base plate. The operating temperature of this stack with 10 PEN layers was 950 C with O2 on the cathode side and H2 on the anode side. Under these conditions the results of the SOFC stack tests were 370 W at a voltage of 0.7 V and a current density of 0.9 A/cm{2}. With this stack test the great improvements, that could be realized by the PEN development, performed within this program, were impressively confirmed. At the same time the usefulness of functional layers between electrodes and bipolar plates within the used planar multiple cell design was proofed.

High technical requirements had to be fulfilled by ceramic component fabrication, by development of glass-ceramic bonding materials and by the material of the bi-polar plate. Activities on these fields have been carried out by the european partners (ECN, NL; GEC Alsthom, UK; and Imperial College, UK) of the CEC sponsored project (JOULE-Programme) and contributed in reaching the project goal in time. The project is pursued aiming at the development of a SOFC-stack of the 20 kW class.
In the EC programme two groups lead by Siemens (contract JOUE-CT90-0048) and ABB (contract JOUE-CT90-0027) are presently developing 1 kW SOFC prototypes according to different concepts. These projects are a first step in the development of MW size SOFC electricity plants which are expected to have efficiencies of 50% or 60% for coal and methane respectively, with a 10-100 times lower pollution than for conventional power plants.

In this project (contract JOUE-CT90-0048) a flat plate 1 kW SOFC unit will be developed with a metal separator plate. This project will be pursued along two lines:

ECN will explore flat plate SOFC cells using wet chemical preparation techniques for the fabrication of the cathode. The component development should result in a 3 layer electrode- electrolyte-electrode composite which will be scaled up to 5 x 5 cm2 and 10 x 10 cm2. As a gas distribution concept a sponge structure of the electrode will be investigated. Know-how developed on the metal separator plate for MCFC (in a parallel nationally funded project) will be used for the development of SOFC metal separator plates.

Siemens, which is the project leader, developed 5 x 5 cm2 SOFC cells under a previous EC contract (EN3E-0176-D). This research work will be continued on cells with mixed oxide cathodes, where gas distribution is brought about by corrugated separator plates. In view of the fact that large ceramic surfaces of 20 x 20 cm2 or 30 x 30 cm2 are difficult to realize. Siemens will investigate the possibility to join 5 x 5 cm2 or 10 x 10 cm2 cells to form larger surface multiple cell plates. After a decision on the selection of the cell concept. Siemens will construct 100 W and 1 kW units. The construction of stacks of multiple cell plates and scaling up, will be the main problems; the testing facilities will be located at Siemens.

This project is a part of a larger project where fundamental SOFC material research will be funded by BMFT and where development of manufacturing methods for SOFC compounds is expected to be funded by BRITE/EURAM.

Coordinator

SIEMENS AG
Address
Wittelsbacherplatz 2
Muenchen
Germany

Participants (3)

ENERGY RESEARCH CENTRE OF THE NETHERLANDS
Netherlands
Address
Westerduinweg 3
Petten
GEC Alsthom Ltd
United Kingdom
Address
Lichfield Road
ST17 4LN Stafford
IMPERIAL COLLEGE OF SCIENCE, TECHNOLOGY AND MEDICINE
United Kingdom
Address
South Kensington Campus
London