Hybrid Ceramic/Metallic Recuperator for SOFC Generators

Solid oxide fuel cells (SOFCs) are one of the most efficient and cleanest power generating systems being developed. A key component is the cathode air heat exchanger, or recuperator, which ensures that the cathode air, and thereby the cells, are at sufficient temperature to permit ion mobility ¿ and thereby improve overall SOFC system efficiency. At present, commercially available metallic recuperators contribute a significant cost to the overall cost of an SOFC generator. This project will develop and demonstrate a ¿hybrid¿ recuperator that combines a high temperature ceramic section with a low temperature metallic section to reduce overall costs, while achieving high effectiveness and long life. The configuration takes advantage of the low fouling capability of a ceramic heat exchanger core at high temperature, while lower grade metallic materials are used in medium-to-low temperature regions. By incorporating both sections into a single unit, costly interconnect ducting and fittings, along with associated support structure and insulation, will not be required. In Phase I, a single pass ceramic monolith was manufactured and tested to determine its heat transfer performance, plenum sealing methods were evaluated, and the system¿s ability to withstand temperature gradients and thermal cycling was determined. The monolith was integrated into a multi-pass, cross-flow recuperator configuration and the effectiveness of the recuperator was determined to be greater than 80%. In Phase II, the ceramic monolith will be further refined to enhance heat transfer performance, and a low cost sealing/attachment arrangement will be implemented. Pre-commercial prototypes will be produced and used to conduct performance and durability testing, and to establish manufacturing techniques and costs. Commercial Applications and Other Benefits as described by the awardee: The ¿hybrid¿ recuperator should significantly reduce the cost of a key component in SOFC generators. It is estimated that a cost reduction of $100/kW, compared with state-of-theart metallic recuperators, can be achieved. The technology also should be applicable to other high temperature applications such as metal melting furnaces, glass furnaces, chemical process reactors, forge furnaces, etc