Fuel cells planar stack design

For portable fuel cells, as used in small consumer electronics, the shape of a common vertical stack is usually not desirable to replace many of the thin batteries currently used. Therefore, a planar stack design is often used, as shown in Figure 6.47. In this design, the passive air flow cathode faces the open air, and the perforated metal cover serves as the current collector. The main issue with this configuration has been limitations in the effectiveness of the electrical connection between adjacent cells, since the path length for electron travel is longer than in a traditional vertical stack design. 

Another possibility to improve fuel utilisation using a simple planar stack design is a series-parallel gas flow system that utilises two different stacks, with the gas flowing through a standard Ni-YSZ based cell stack first, with a reasonable, but safe utilisation, followed by an oxide based ceU stack to extract the last of the unused fuel from the exhaust. 

SOFC are produced with either tubular or planar stack configurations investments for planar design are a rough estimate, as no prototypes exist. Specific investments for PAFC are in the range 4000- 4500/kW (IEA, 2007). For further fuel-cell R D needs see IEA (2005). 

Planar SOFC, in particular, monolithic designs (MHI) are capable of high (volumetric) power densities most favoured by direct and short current paths across the stack components. The PEN is principally square, rectangular and circular (Ceramic Fuel Cells Limited (CFCL), Mitsubishi Materials Corp., SulzerHexis) in shape with active surface areas of 100-200 cm2 (15.5-31 in2). A drawback of this design is that it often necessitates the use of high temperature sealants for application at the in-... 

The design of BP for PEMFCs is dependent on the cell architecture, on the fuel to be used, and on the method of stack cooling (e.g., water or air-cooling). To date, most of the fuel cells have employed traditional filter-press architecture, so that the cells are planar and reactant flow distribution to the cells is provided by the bipolar plate. The bipolar plate therefore incorporates reactant channels machined or etched into the surface. These supply the fuel and oxidant and also provide... 

FIGURE 11.1 Planar design of solid-oxide fuel cell (a) a stack repeat unit and (b) details of a possible design. 

Figure 3.20 shows a cylindrical layout often used for high-temperature SOFCs. Alternatives are a stack of planar cells or a disk concept with feed tubes in the centre. A consideration of efficient heat exchange is the cormnon design strategy for the high-temperature fuel cell geometry. 

Different shapes serve different purposes. Block stacks are convenient to use in some applications and planar stacks are easier in others For instance, a laptop computer would do well to use a planar configuration rather than a block configuration. Generally, fuel cells can come in any imaginable shape and size, and be designed specifically for a wide variety of applications. 

A good start is to construct a 12 volt 10 ampere power supply, which can be constructed with either planar or block stacks, as discussed in Build Your Own Fuel Cells. Whatever design you choose, this project will... 

Figure 9.14 (a) An expanded view of a stack of planar design solid-oxide fuel cells (SOFCs) (b) tubular design of an SOFC (c) a stack of tubular SOFCs... 

Most developers focus on a diffusion-driven air supply with air breathing cathodes. This can be realized by planar fuel cell designs, where the cells are not stacked, as in high-power fuel cells, but rather are oriented side-by-side in one plane (Figure 5.3). 

Duquette, J. and Petrie, A. (2004) Silver wire seal design for planar solid oxide fuel cell stack. J. Power Sources, 137, 71-75. 

Lin, C.K., Huang, L.H., Chiang, L.K., and Chyou, Y.P. (2009) Thermal stress analysis of planar solid oxide fuel cell stacks effects of sealing design. J. Power Sources, 192, 515-524. 

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