Tubular Cell Stack

The stack is partitioned in elevation by porous baffles forming a fuel distribution plenum, an active cell zone, a spent fuel plenum, a combustion zone, and an air plenum. An ejector using pressurised desulphurised natural gas as the 

Combustion Plenum Depleted Fuel Plenum Thermocouple Internal Reformation Zone 

I ifjure H.20 Thermul and hi/draulie features of the 100 kWSOFC slack 126 /. 

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FIGURE 3.3 Series-connected tubular cell stack. 

The single biggest advantage of tubular cells over planar cells is that they do not require any high-temperature seals to isolate oxidant fi om the fuel, and this makes performance of tubular cell stacks very stable over long periods of times... 

Figure I. 12 Fuel Cell Technologies 5 kW. system, built using Siemens Westinghouse tubular cell stack.

The segmented cell in series design is being investigated by Mitsubishi Heavy Industries (Japan), ABB, and Rolls Royce. This cell contains segmented cells arranged in a thin, banded structure on a porous support alumina tube. The sealing is provided by the interconnect, which also serves as an electrical contact between the cathode of one cell and anode of the next cell (Fig. 4.18). The oxidant flows outside and the fuel flows from one cell to the next inside the tubular cell stack. 

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,... 

A configuration for electrically connecting tubular cells to form a stack is described in Section 8.1.2 under sealless tubular configuration (Figure 8-6). The cells are connected in a series-parallel array by nickel felt strips that are exposed to the reducing fuel gas. In this arrangement, the nickel felt strips and cell interconnections extend the length of the cell. 

The fuel gas composition also has a major effect on the cell voltage of SOFCs. The performance data (33) obtained from a 15 cell stack (1.7 cm active electrode area per cell) of the tubular configuration (see Figure 8-1) at 1000°C illustrate the effect of fuel gas composition. With air as the oxidant and fuels of composition 97% H2/3% H2O, 97% CO/3% H2O, and 1.5% H2/3% CO/75.5% CO2I2OV0 H2O, the current densities achieved at 80% voltage efficiency were -220, -170, and -100 mA/cm, respectively. The reasonably close agreement in the current densities obtained with fuels of composition 97% H2/3% H2O and 97% CO/3% H2O indicates that CO is a useful fuel for SOFCs. However, with fuel gases that have only a low concentration of H2 and... 

Ciano C., Cali M., Melhus O., Verda V., 2006. A model for the configuration design of a tubular Solid Oxide Fuel Cell Stack. ASME Paper IMECE2006-16141, Chicago, IL, November 5-10, 2006. 

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.

Four expressions can be considered to obtain the view factors for modeling tubular cells and stacks ... 

Saito T., Abe T., Fujinaga K., Miyao M., Kuroishi M., Hiwatashi K., Ueno A. (2005) Development of tubular SOFC at TOTO. In Proceedings - Electrochemical Society, v PV 2005-07, Solid Oxide Fuel Cells IX Cells, Stacks, and Systems, Proceedings of the International Symposium, ECS, Electrochemical Society Inc., pp. 1039-1040. 

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