Siemens Westinghouse cells

Canada Ontario Hydro has tested a single Siemens-Westinghouse cell for 1725 hours. Over 1425 of the hours were at elevated pressure of 5 atm. 

A schematic cross-section of the Siemens Westinghouse cell is shown in Figure 7-11. Air is fed through an alumina feed tube, while fuel is supplied externally. The cell length has been gradually increased from 30 cm to about 150 cm. The cell has a diameter of 1.27 cm. 

Tubular cells, identical in design to that of Siemens Westinghouse cells, are also being developed by Toto Ltd of Japan they use a wet slurry dip/sintering method for depositing cell components on the cathode tube to reduce the manufacturing cost of the cells [30-34], However, the performance and performance stability with time of these cells still need improvement. 

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. 

The Siemens Westinghouse TSOFC commercialization plan is focused on an initial offering of a hybrid fuel cell/gas turbine plant. The fuel cell module replaces the combustion chamber of the gas turbine engine. Figure 1-8 shows the benefit behind this combined plant approach. Additional details are provided in Section 8. As a result of the hybrid approach, the 1 MW early commercial unit is expected to attain -60% efficiency LHV when operating on natural gas. 

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... 

Siemens Westinghouse, in conjunction with Ontario Hydro Technologies, tested AES cells at pressures up to 15 atmospheres on both hydrogen and natural gas (22). Figure 8-8 illustrates the performance at various pressures ... 

This natural gas fuel cell power system is based on a pressurized TSOFC combined with a combustion turbine developed by Siemens Westinghouse (52). Most TSOFC power plant concepts developed to date have been based on atmospheric operation. However, as shown in... 

Section 8, the cell voltage increases with cell pressure. Thus, operating with an elevated pressure will yield increased power and efficiency for a given cycle. In addition, the use of a pressurized SOFC will also allow integration with a combustion turbine. The combustion turbine selected for integration by Siemens Westinghouse is the unique 1.4 MW Heron reheat combustion turbine, a proposed product of Heron (53). 

Figure 9-23 Diagram of a proposed Siemens-Westinghouse hybrid system (Taken from DOE Project Fact Sheet - Fuel Cell/ATS Hybrid Systems)...

Siemens-Westinghouse Power Corporation, of Pittsburgh, PA, with a subcontract to Allison Engine Company, evaluated a pressurized solid oxide fuel cell coupled with conventional gas turbine technology without a steam plant. The system was operated at a pressure of 7 atm. The fuel cell generated 16 MW of power and the gas turbine generated 4 MW of power. The process showed 67 % efficiency as developed. An efficiency of 70 % is deemed achievable with improvement in component design. The COE is predicted to be comparable to present day alternatives. NOx levels were less than 1 ppm. 

Siemens-Westinghouse Power Corporation, Pittsburgh, PA, and Solar Turbines developed a conceptual design of an economically and technically feasible 20-MW, 70-% efficient natural gas-fueled power system that employs solid oxide fuel cells operating at elevated pressure in conjunction with an Advanced Turbine System gas turbine. The fuel cell, operated at 9 atm pressure, generated 11 MW of power. Two Solar Mercury 50 gas turbines were used to generate 9 MW of power. The results of the study indicated a system efficiency near 60 %. A low COE relative to conventional power generation is predicted. 

Siemens-Westinghouse Power Corporation of Pittsburgh, PA developed and fabricated the first advanced power plant to combine a solid oxide fuel cell and a gas turbine. The microturbine generator was manufactured by Northern Research and Engineering Corporation of Woburn, Mass. The factory acceptance test was completed in April 2000. Southern California Edison will operate the new hybrid plant at The National Fuel Cell Research Center at the University of California-Irvine. A year of testing in a commercial setting will be performed at this site. The system cycle is expected to generate electric power at 55 % efficiency. 

A 320-kilowatt hybrid system is also in the planning stages. An initial commercial offering of a one MW fuel cell-microturbine power plant in late 2002 will be the end results of this Department of Energy/Siemens Westinghouse partnership program (70). 

This section of the handbook contains field site information. Most of the worldwide summaries were extracted from an lEA paper. Information on the U.S. Department of Defense (DoD) Fuel Cell Demonstration was taken from the following web site www.dodfuelcell.com. Finally, Fuel Cell Energy, IFC, and Siemens Westinghouse provided information on their field sites. The IFC PAFC summary includes a number of projects reported by DoD. In the DoD demonstration program, a total of 30 PAFC units were installed at DoD sites across the United States. These were model B and C PC-25 units. 

Siemens Westinghouse provided DOE with information on their fuel cell field units. This information is provided in Table 11-6. 

Any one of the three components in SOFC, the cathode, anode, or electrolyte, can provide the structural support for the cells. Traditionally, the electrolyte has been used as the support however, this approach requires the use of thick electrolytes, which in turn requires high operating temperatures. Electrode-supported cells allow the use of thin electrolytes. The Siemens—Westinghouse Corporation has developed a cathode-supported design,although this has required electrochemical vapor deposition of the YSZ electrolyte. Most other groups have focused on anode-supported cells. In all cases, it is important to maintain chemical compatibility of those parts that come in contact and to match the thermal expansion coefficients of the various components. A large amount of research has been devoted to these important issues, and we refer the interested reader to other reviews. 

Policy Studies on infrastructure considerations and transition management activities include (a) Fuel Cell RD D activities (b) SOFC and PEMFC cells, stacks, systems are being developed in relation to local generation (c) Systems field testing is being undertaken by Siemens-Westinghouse, Sulzer, and Plug-Power. 

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... 

George, R. and Casanova, A., Developments in Siemens Westinghouse SOFC program, in Proceedings of2003 Fuel Cell Seminar, 2003, p. 895. 

Unlike molten carbonates, solid oxides use a hard ceramic electrolyte instead of a liquid. That means the fuel cell can be cast into a variety of useful shapes, such as tubes. With higher temperatures, sofcs may be able to cogenerate steam at temperatures as high as i,ooo°f. The Siemens Westinghouse Power Corporation has built the first advanced hybrid system, which combines a gas turbine with a tubular sofc. As of 2003, the 220 kW hybrid system has operated in California for more than 2,000 hours with a respectable 53 percent efficiency, comparable to current combined cycle gas turbines. The ultimate goal is an efficiency of 70 percent or more. 

Tubulav geometry The following discussion draws specifically on the Siemens-Westinghouse [13] programme. The arrangement of the cell components is illustrated in Fig. 4.32(a). 

Siemens Westinghouse is a major player, with its all-ceramic large-diameter tubular fuel cells. These are to be deployed with integrated gas turbines (Section 4.2). 

Siemens Westinghouse is advanced in its pursuit of gas turbine integration. High-temperature depleted air and unused fuel from the fuel cell cannot be discarded, and are best used in a gas turbine, as outlined in Baozhen Li etal. (2001), the Siemens patent for a Single Module Pressurised Fuel Cell Turbine Generator System (pp. 974-979). The effect... 

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