Stacks with Tubular Cells

Especially for high-temperature fuel cells, stacks with tubular cells have been developed. 

Although cathode-supported tubular SOFCs in large-scale stacks are the type of SOFC stack most widely commercialized, recent alternative tubular cell designs have been developed with anode-supported designs for smaller-power applications. Cells in these stacks have diameters on the order of several millimeters rather than centimeters,... 

Figure 4.14. Separation of cell lysates containing pharmaceutical products, employing large-capacity centrifuges that are configured with tubular bowl (A), multi-chamber bowl (B), disc stack bowl (C), or decanter (scroll) bowl (D).

Fig. 5.1 Commonly used SOFC designs (Celik, 2006). (a) Tubular SOFC, (b) 24 cell tubular SOFC stack, (c) a tubular SOFC module with 48 stacks, (d) 28 cell internally manifolded stack design by Versa Power Systems.

A 1 kW SOFC prototype based on tubular cells was designed, manufactured and tested in 1989. The cell had a working surface of 63 cm2 and a mean power 12.5 W or 0.2 W/cm2 at 900°C. 16 cells were assembled into a stack. The prototype consisted of 6 stacks. The prototype was fed with methane internal partial oxidation was used for fuel processing. The prototype worked at fuel utilization of 0.9 and had efficiency about 40%. 

The single tubular cell with 1.6-mm diameter and 1-cm length, generated about 140, 300, and 350 mW at 500, 550, and 570°C with Hj fuel, has been reported. This indicates that a cell stack of 55-cell arrangement whose volume is about 1 cm can possibly generate 3.5, 7.5, and 8.7 W at 500, 550, and 570°C, respectively, using the microtubular cells [8]. 

FIGURE 3.2.12 (a) Tubular cell used by Siemens-Westinghouse. (Reprinted from Singhal, S. C. (2000). Solid State Ionics, 135, 303-313 with permission from Elsevier Science.) (b) Sketch of a simple planar design. (Erom Ref. [193, Eig. 12.27].) (c) A cross-flow monolithic stack design. (J. Am. Ceram. Soc. by N. Q. Minh. Copyright 1993 by Am. Ceram. Soc. Inc. Reproduced with permission of Am. Ceram. Soc. Inc. in the format Other Book via Copyright Clearance Center.)... 

The above results were for SOFC buttrui cells, and more work is needed to demonstrate direct-methane utilization in stacks. One step towards this goal is simulation of stack operation. Such results indicate that in a tubular stack with a barrier layer over the first 30 % of the fuel-flow field, the anode-gas composition is maintained in the thermodynamically non-coking regime. Furthermore, the direct-methane feed case yielded overall stack performance nearly as good as the anode recycle case [33]. 

Yoshida S, Kabata T, Nishiura M, Koga S, Tomida K, Miyamoto K, Teramoto Y, Matake N, Tsukuda H, Suemori S, Ando Y, Kobayashi Y (2011) Development of the SOFC-GT combined cycle system with tubular type cell stack. ECS Trans 35( 1) 105-111... 

This entry is organized as follows In section Historical Aspects of Reliability, Durability and Cost Issues, historical aspects are first described to provide essential points of SOFC stack/system development. The technological features of the first-generation cells, namely, sealless tubular cells, will be described in comparison with the second- and the third-generation cells in critical technological issues these are materials selection of interconnect (oxide or metal), sealing scheme, redox issues of nickel cermets, metal support cells, trade-off relation between reliability and performance, and materials chemistry associated with lowering operation temperature. 

Fig. 18.8 Impurities in anodes for four SOFC stacks with different materials and designs. Impurities were determined with SIMS on the 24 h operation and on the longer (about 5,000 h) operations, (a) High-temperature segment-in-series cell by MHI, (b) intermediate flatten tubular cell by Kyocera, (c) high temperature sealless tubular cells by TOTO, and (d) intermediate temperature disk-type planar cells by Mitsubishi Materials corp...

As described in the introduction, SOFC stack development started with the breakthrough by Westinghouse the sealless tubular cells can be categorized as stable but expensive stacks. Since then, many efforts have been focused on reducing the fabrication cost in the first-generation cells. 

To avoid the packing density limitations associated with cylindrical cells, some tubular stack designs use flattened tubes. 

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