FUEL 254 |
| The performance of solid oxide fuel cells (SOFCs) is affected by various polarization losses, namely, ohmic polarization, activation polarization and concentration polarization. Under given operating conditions, these polarization losses are largely dependent on cell materials, electrode microstructures, and cell geometric parameters. Most of the reported work, however, has often focused on the role of new materials (compositions) – but not on the relevant parameters within a given materials set. As a result, often observed differences in cell performance are attributed to differences in materials, without regard to geometric and microstructural parameters. In this study, solid oxide fuel cells (SOFC) with yttria-stabilized zirconia (YSZ) electrolyte, Ni-YSZ anode support, Ni-YSZ anode interlayer, strontium doped lanthanum manganate (LSM)-YSZ cathode interlayer, and LSM current collector, were fabricated. The effect of various parameters on cell performance was evaluated. The parameters investigated were: (1) YSZ electrolyte thickness, (2) Cathode interlayer thickness, (3) Anode support thickness, and (4) Anode support porosity. Cells were tested over a range of temperatures between 600 and 800oC with hydrogen as fuel, and air as oxidant. Ohmic contribution was determined using the current interruption technique. The effect of these cell parameters on ohmic polarization and on cell performance was experimentally measured. Dependence of cell performance on various parameters was rationalized on the basis of a simple analytical model. Based on the results of the cell parameter study, a cell with optimized parameters was fabricated and tested. The corresponding maximum power density at 800oC was ~1.8 W/cm2. The present underscores the importance of microstructural and geometric issues. These results are used to design cells with even higher power densities. It can be shown that cells with power densities approaching 3 W/cm2 at 800oC are in principle possible. |
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Fuel Cell Chemistry and Operation
9:00 AM-12:10 PM, Thursday, 14 September 2006 Palace -- Gold Ballroom, Oral
Division of Fuel Chemistry |