Siemens cell

The Siemens cell was similar except that the air electrode was fabricated with two layers a hydrophilic layer of porous nickel on the electrolyte side for oxygen evolution and a hydrophobic layer [carbon black bonded with Teflon (PTFE) and catalyzed with silver] on the air side for oxygen reduction. The dual porosity helped to shield the silver catalyst from oxidation. As many as 200 cycles were achieved. ... 

PV systems consist of arrays of cells that ate interconnected in panels or modules to increase total power output. Often the systems include sun-tracking equipment, as well as power-conditioning equipment to convert dc to ac. The systems can range in size from a simple one-panel, fixed-orientation unit to a vast field of modules that accurately track the movement of the sun. Electric utiUties in Europe, Japan, and the United States have hosted several experimental PV power plants. The largest to date was a 5.5-MW plant at Carrisa Plains, California, built by Siemens Solar Industries (formerly ARCO Solar). 

Investigations at Siemens in Erlangen, Germany, have used unsupported platinum-ruthenium anodes (4 mg/cm ) and platinum black cathodes (4 mg/cm ). Their best performances were 0.52 V at 400 mA/cml At Los Alamos National Laboratory in New MexicoJ the electrocatalyst was unsupported R-RuOx at the anode and unsupported R black at the cathode (R loading about 2 mg/cm ). In a subsequent study, the thinner Nafion 112 membrane was used to reduce the ohmic drop. Under pressure at 400 mA/cm cell potentials of 0.57 V with Oj and 0.52... 

X-ray single crystal analysis Data collection. Siemens SMART IK CCD. Diffractometer. Data collection by SMART (Siemens, 1995) cell refinement SMART data reduction SAINT (Siemens, 1995) program(s) used to solve structure SHELXS97 (Sheldrick, 1997) program(s) used to refine structure SHELXL97 (Sheldrick, 1997) molecular graphics XP in SHELXTL (Sheldrick,... 

Using three spherical crystals - the standard ylide crystal provided by Siemens Analytical Instrumentation, ruby and ammonium hydrogen tartrate (Enraf-Nonius standard crystal) - such an experiment has been carried out using two SMART CCD diffractometers. Before integration [8], all of the cell axes were multiplied by 2. Duplicate measurements were then averaged, and all odd reflections with values of F2 > 15 esd s were compared with the reflection with double the indices to obtain the best value of k for the expression F kl = kF h2k2). The average values of k obtained for the two diffractometers were 0.0014(2) and 0.00106(5). 

There are several approaches to measuring electrolyte sensors [13], ultrasonic methods (acoustical), photo-acoustic cells [14] (Siemens C02 Controller), optical IR-detection and liquid-state electrochemical... 

FIGURE 6.5 Tubular cathode-supported solid oxide fuel cell developed by Siemens Power Generation [48]. Reprinted from [48] with permission from Elsevier. 

Siemens Power Generation is a partner with ConocoPhillips and Air Products and Chemicals, Inc., (APCI) to develop large-scale fuel cell systems based upon their gas turbine and SECA SOFC technologies. The design will use an ion transport membrane (ITM) oxygen air separation unit (ASU) from APCI with improved system efficiency. 

Companies such as United Technologies Corp. (UTC), Ballard Energy Systems, Plug Power, M-C Power, AlliedSignal, and Siemens-Westing-house have been developing fuel cell products for the commercial market and may be impacted by this trend. 

Despite this, the principle of the fuel cell was not able to be developed into a technically mature process for a long time. The main reasons, apart from insufficient knowledge of the electrochemical processes involved, were material problems. Around the turn of the century, the dynamo generator (1866, Siemens), combustion... 

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. 

Fig 4-1 is a schematic depicting the operating configuration of the alkaline fuel cell (Siemens). The half-cell reactions are ... 

Figure 4-1 Principles of Operation of Alkaline Fuel Cells (Siemens)...

AFC cell stacks have demonstrated sufficiently stable operation for at least 5000 hours, with degradation rates of 20 V per hour or less (20). Siemens has reported a total of >8000 operating hours with approximately 20 units (22). For large scale utility applications, economics demand operating times exceeding 40,000 hours which presents perhaps the most significant obstacle to commercialization of AFC devices in the realm of interest to the DOE Stationary Electric Power Program. 

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. 

---