Characterization of Solid Oxide Fuel Cells with LSCF-SDC Composite Cathodes

This paper reports the study of an anode-supported SOFC cell containing an LSCF-SDC composite cathode. The SOFC cell was tested at different temperatures and reactant flow rates. After testing, the cell was sectioned and characterized using SEM/EDS. Such analysis indicated that no structural damage and no significant interdiffusion of elements among the layers occurred. The measured electrochemical performance data at different temperatures indicate an Arrhenius behavior or temperature activated processes. The low-porosity anode functional layer appears to be very sensitive to low hydrogen contents. The electrochemical performance is also affected by changing air flow rates

XPS Studies of LSCF Interfaces afer Cell Testing

The motivation of this investigation is to explore the possibility of using the depth profile capability of XPS to study interfaces after SOFC button cell testing. The literature uses XPS to study various cathode materials but has devoted little to the understanding of various cathode interfaces especially after testing. In this work, an SOFC button cell is first tested, and then, the LSCF cathode, barrier layer, and electrolyte are sputtered away to study the behavior of different interfaces. This work has shown that some elements have moved into other layers of the SOFC cell. It is argued that the migration of the elements is partly due to a redeposition mechanism after atoms are sputtered away, while the rest is due to interdiffusion between the SDC and YSZ layers. However, additional work is needed to better understand the mechanism by which atoms move around at different interfaces. The cell electrochemical performance is also discussed in some details but is not the focus

Surface-to-Surface Radiation Exchange Effects in a 3D SOFC Stack Unit Cell

This paper reports a new study where radiation effects are studied in details in an SOFC stack. The 3D model used includes and couples fluid dynamics, electrochemistry, electrical conduction, diffusion, and heat transfer physics. The model was built using in-house experimental voltage-current density data for validation purposes. The objective of this study is to understand the effects of radiation in the flow channels of SOFC stacks. Both gas radiation and surface-to-surface heat exchange are considered. This study indicates that gas radiation is negligible when compared to surface-to-surface heat exchange. It is also found that surface-to-surface heat exchange cannot be neglected and actually provides a more uniform temperature distribution along the SOFC stack. Heat transfer via convection is also significant and should be included when modeling similar situations. Finally, the model indicates that viscous dissipation is a negligible source of heat generation

The Electrical Performance of a 5-Cell Planar SOFC Stack

In this paper the electrochemical performance of a 5-cell planar SOFC stack is reported and discussed. Voltage-current density curves were measured at two temperatures and at different fuel utilizations. The temperature and fuel utilization effects on the individual cell’s performance are discussed. A fuel sensitivity analysis is reported as well, and its effect at different current level is discussed. Finally the lifetime performance of the stack is discussed where the voltage-time profile is shown

Surface-to-Surface Radiation Exchange Effects in a 3D SOFC Stack Unit Cell

This paper reports a new study where radiation effects are studied in details in an SOFC stack. The 3D model used includes and couples fluid dynamics, electrochemistry, electrical conduction, diffusion, and heat transfer physics. The model was built using in-house experimental voltage-current density data for validation purposes. The objective of this study is to understand the effects of radiation in the flow channels of SOFC stacks. Both gas radiation and surface-to-surface heat exchange are considered. This study indicates that gas radiation is negligible when compared to surface-to-surface heat exchange. It is also found that surface-to-surface heat exchange cannot be neglected and actually provides a more uniform temperature distribution along the SOFC stack. Heat transfer via convection is also significant and should be included when modeling similar situations. Finally, the model indicates that viscous dissipation is a negligible source of heat generation

Senator

Dr. Gianfranco DiGiuseppe Professor of Mechanical Engineeringhttps://digitalcommons.kettering.edu/fs_currentmembers/1015/thumbnail.jp

Seal Leakage Effects on the Electrical Performance of an SOFC Button Cell

This paper reports a new study where leakages through a seal in an SOFC button cell is investigated in details. A 2D model is used to determine different flow characteristics of the leakages and its effects on the cell performance. The leakage effects on the performance are studied at different seal porosities and other parameters are also investigated. The results of this investigation indicate that a seal leakage can affect the cell performance significantly if the leak comes from outside the test rig. That is, an air leak must be present through the seal and must flow into the anode chamber where then it affects negatively the cell performance

An Electrochemical Model of a Solid Oxide Fuel Cell Using Experimental Data for Validation of Material Properties

This paper reports an electrochemical model of a Solid Oxide Fuel Cell where the model is compared against experimental data using the results from a button cell electrical test. The model fits the experimental data reasonably well using material properties found in the literature. Some of the material properties were used as fitted parameters to improve the fit, and their values compared with reported measured values. Further, cell polarization losses are explored to determine which one influences the voltage-current density characteristics the most. In comparing the material properties found in the literature with the one appropriate for the model curve fit to the experimental results, some discrepancies were observed. Hence, a better methodology is needed to understand the actual cell behavior and where improvements are needed. The method developed here is very useful for a commercial supplier of Solid Oxide Fuel Cells where button cells taken from a batch can be used to determine how good the cells are before they are installed in a stack

Seal Leakage Effects on the Electrical Performance of an SOFC Button Cell

This paper reports a new study where leakages through a seal in a solid oxide fuel cell (SOFC) button cell is investigated in detail. A 2D model is used to determine different flow characteristics of the leakages and its effects on the cell performance. The leakage effects on the performance are studied at different seal porosities, and other parameters are also investigated. The results of this investigation indicate that a seal leakage can affect the cell performance significantly if the leak comes from outside the test rig. That is, an air leak must be present through the seal and must flow into the anode chamber, where then it affects negatively the cell performance. In addition, the model developed here can be used to include leakages in stack modeling studies