Abstract
Solid oxide fuel cell (SOFC) is attractive due to the excellent power generation efficiency and fuel flexibility. Conventional ceramic electrolyte and anode supported SOFC (AS-SOFC) is limited to stationary power generation applications as a result of the difficulty of quick startup and the high operating temperatures of 700 to 1000 °C. If quick startup of a SOFC is realized, mobile applications may be considered. To enable this, it is important to shorten the start-up time and reduce the heat cycle performance degradation and stack power density both in terms of weight and volume. As an approach to solving these problems, metal supported SOFC (MS-SOFC) has attracted attention. The development of this new generation of SOFC is currently in progress. DTU Energy’s MS-SOFC technology is based on co-sintering of laminated tape casted electrolyte, anode and support layers in a reducing atmosphere. This implies that the sintering shrinkage of the different layers should be matched sufficiently so that the mechanical stresses originating from any mismatch in sintering shrinkage of the individual layers during sintering can be absorbed by the cell structure. If the cell structure is unable to absorb the mechanical stresses, the cell will crack. Perfect matching of sintering shrinkage of the layers is practically very difficult as e.g. the electrolyte layer needs to be completely dense and thus gas tight, while the anode and support layers in contrast needs to be highly porous to allow sufficient gas transport. In the present study, we report on efforts of reducing the metal support thickness in DTU Energy´s MS-SOFC design. This is done to reduce the stack thermal mass during heat up and to increase the stack power density in terms of weight and volume. The results show an increased densification of the metal support layer as the support layer thickness is gradually reduce from 313 μm to 108 μm. This is due to sintering constraint. To counteract the metal support layer densification, the feasibility of creating gas channels within the support layer is explored. The gas channels are in this particular approach prepared by the creation of holes in the green tape casted support layer via puncturing. The study shows, that it is possible to lower the support thickness and thus the cell thickness. The study also shows that it is possible to counteract the increased support layer densification and resulting performance loss by the creation of gas channels in the support layer.
Highlights
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From early publication within Ceres Power’s relatively long history it is possible to get a substrate thickness of 300 μm from a modelling study in 2005.14 The performance of the different metal support (MS)-Solid oxide fuel cell (SOFC) designs are for various reasons difficult to compare for among other reasons very different aimed operation temperatures e.g. Plansee 800◦C and DTU 650–700◦C
The ScYSZ layer sintering starts at a lower temperature than the sintering of the anode and support layer
Summary
General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. DTU Energy’s MS-SOFC technology is based on co-sintering of laminated tape casted electrolyte, anode and support layers in a reducing atmosphere. This implies that the sintering shrinkage of the different layers must be matched sufficiently so that the mechanical stresses originating from any mismatch in sintering shrinkage of the individual layers can be absorbed by the cell structure. The company Ceres Power founded in 2001 is at present the organization, which most effectively has demonstrated up scaled large cell sized >80 cm[2] MS-SOFC stack technology This is followed by consortia involving the company Plansee. The second route is modification of the sintering profile Realizing this may serve as a means of enabling faster startup and increase the stack power density in terms of weight and volume
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