Westinghouse tubular cell

Sealless Tubular Configuration The most developed solid oxide fuel cell is the Siemens Westinghouse tubular cell. This approach results in eliminating seal problems between adjacent cells. A schematic representation of the cross section of the present Siemens Westinghouse... 

An immediate comparison with the Siemens Westinghouse tubular cell reveals that the Rolls-Royce arrangement is likely to be relatively compact. In Figure 4.4 cells, gas passages and dimensions are apparent. 

Fig. 7. Solid oxide fuel cell configurations. A Siemens-Westinghouse tubular cell B Tubular integrated interconnector concept. Similar interconnected systems exist in planar geometry C Planar SOFC designs, differing only in gas flow manifolding.

Lanthanum chromite has provided long lifetimes, as long as 69,000 h in Siemens Westinghouse tubular cells, at 900-1000°C. However, metallic interconnects have not yet shown equivalent lifetime performance. Improvements in metallic interconnect compositions and contact layers between cells/interconnects are still issues for materials development. In particular, the metal/ceramic interface in cells should have low corrosion, low contact resistance and low permeability of chromium species. Recent results have shown that optimised steels for SOFC applications are available and alkaline earth-free and cobalt-containing perovskites are the most suitable materials for contact layers however, their long-term performance under fuel cell operation conditions needs to be proven. 

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

Siemens Westinghouse Power Corporation (SWPC) has three TSOFC systems employing tubular cell technology operating on user sites. All were produced in their Pittsburgh, Pennsylvania facility. The capacities of the systems are 220 kilowatts, 100 kilowatts, and 25 kilowatts. 

Other manufacturers have proposed different solutions. The cell manufactured by Acumentrics is similar to the Siemens Westinghouse tubular SOFC the differences mainly reside in the fuel flowing inside the cell without inlet pipe and in the tube having open ends. Reforming is internal to the tube. The Acumentrics cell operates in the same temperature range than the previously mentioned SOFCs, but... 

Goal of a joint Dutch/Danish project is the installation and operation of a 100 kW SOFC power plant to be connected to the electricity grid in The Netherlands. Based on the Westinghouse tubular design, the stack consists of 1152 fuel cell tubes which have a lengdi of 1.5 m and a diameter of 2.2 cm. Testing of this SOFC unit was successfully done over 300 hours. It was put into operation at the end of 1997. The efficiency is expected to approach 47 % at 100 kW(e). If in addition the waste heat of 150 kW could be utilized in a gas turbine, the overall efficiency could be raised to 70 % [15]. 

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.)... 

Solid Oxide Fuel Cells, History, Fig. 4 Alternate geometry tubular cells investigated by Siemens Westinghouse... 

After knowing the success of Westinghouse and technological assessments by ANL, many people started to develop various kinds of SOFC stacks to overcome demerits of the sealless tubular cells. Depending on their technological strategies, several different attempts have been made. These can be summarized as follows ... 

Westinghouse) themselves [27]. To lower the fabricaticMi cost, sintering-wet process has been successfully adopted by TOTO [28], whereas atmospheric plasma spray was adopted by Siemens themselves [27]. These attempts are based on the idea that tubular cells or their modified cells must be superior to other designs. 

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. 

The remainder of this section on tubular SOFC focuses on the cell design furthest advanced in its development the Siemens Westinghouse tubular SOFC technology. 

---