Cell and Stack Design

Large planar cells display two other problems which cause concern. The first is the difficulty of making and handling large areas of delicate sheets the maximum 

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Manufacturing details of the Ballard Power Systems cell and stack design are proprietary (18), but the literature provides some information on the cell and stack design. An example schematic of a manufacturer s cell is shown in Figure 3-1. 

The Forschungszentrum Jiilich (FZJ) in Germany has been active in the field of SOFC technology since 1990. Research work includes all aspects from materials development and characterisation, over cell and stack design, modelling and manufacturing, to testing of cells, stacks and systems. 

The Arrhenius law prescribes an exponential temperature growth of the rates of all transport and kinetic processes in a fuel cell. The laws of temperature distribution are thus of great interest for cell and stack design. 

Kendall K, Minh NQ, Singhal SC (2003) Cell and stack designs. In Singhal SC, Kendall K (eds) High temperature solid oxide fuel cells - fundamentals, design and applications. Elsevier, Oxford, UK... 

In addition to the stack, practical fuel cell systems require several other sub-systems and components the so-called balance of plant (BoP). Together with the stack, the BoP forms the fuel cell system. The precise arrangement of the BoP depends heavily on the fuel cell type, the fuel choice, and the application. In addition, specific operating conditions and requirements of individual cell and stack designs determine the characteristics of the BoP. Still, most fuel cell systems contain ... 

Broadly, interconnect materials for SOFC fall into two categories conductive ceramic (perovskite) materials for operation at high temperature (900 to 1000 °C) and metallic alloys for lower temperature operation. Though the shape of SOFC interconnects depends heavily on the cell and stack design, the materials choice is almost entirely determined by physical and chemical stability under operating conditions. 

Given the error and experimental effort associated with estimation of all the parameters in the analytical model and the complexity and time required for computational simulation, which, ultimately, still relies on the accuracy of the input parameters, there is a need for an entirely empirical approach to quickly characterize performance of fuel cells and stack designs. The following semiempirical model can be used to quickly glean some comparative information ... 

The ideal efficiency AG/AH may be considered a measure of the thermodynamic reversibility of the reaction and depends only on the operating temperature and fuel used. It is typically between 80 and 100%. The voltage efficiency and fuel utilisation, as welt as the electrical energy efficiency, are useful measures for the success of the cell and stack design. 

Electro-analytical Tools in Single Cell and Stack Design... 

Kendall, K., Minh, N.Q. and Singhal, S.C. (2003), Cell and stack design. High Temperature Solid Oxide fuel Cells Fundamentals, Design and Applications, Eds. S.C. Singhal and K. Kendall, Elsevier, UK, p. 197-228. 

Since metal-supported SOFCs have an intrinsically different mechanical behaviour, compared to ceramic components, it makes them potential candidates for withstanding the extrinsic acmal loads such as temperature gradients and mechanical stresses whether static or dynamic. The predictable material properties of metals make them more suitable in connection with effective use of FEM modelling in order to obtain optimal cell and stack designs. The numbers of R D activities related to the so-called metal-supported SOFC (also called third generation SOFC) have increased significantly in recent years [31]. 

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