In this work a Solid Oxide Fuel Cell (SOFC) test stand was developed for testing commercially available anode supported cells with an active area of 81 cm2 under pressurized conditions up to 98 PSIG, with temperatures ranging from 600 °C – 750 °C. A custom stack architecture was developed utilizing disposable 430 S.S interconnect plates, and sealing is accomplished using only compressible gaskets. An in-situ technique was developed using impedance measurements during stack compression at room temperature to ensure proper compression of the stack is achieved.
In house electrodeposited Co-Mn coatings were developed to prevent chrome evaporation at the cathode and increase conductivity. The cell performance with and without the coating was compared. The cells were characterized using polarization curves as well as in-situ impedance measurements with a subsequent Distribution of Relaxation Times (DRT) analysis. The results show a significant improvement in performance up to about 48 PSIG which can be attributed to reductions in activation and gas diffusion losses. Further increases in pressure after 48 PSIG show diminishing returns in performance.
Additionally, a time domain impedance spectrometer was developed which utilizes Passive Load Excitation (PLE) to obtain the impedance spectrum of the cell. Custom MATLAB software was developed to transform the time domain response of the cell into the frequency domain via a carrier function Laplace transform. The MATLAB software was validated using a commercial circuit simulating software, which simulated an RC dummy cell in both a time transient analysis and frequency domain analysis. The MATLAB software correctly converted the time transient response of the simulated circuit into the frequency domain. The spectrometers hardware was validated by comparing its measured response of SOFC button cells and NiMH battery packs to measurements of the same cells using a commercially available AC impedance spectrometer.
|Commitee:||Norton, Grant, Leachman, Jacob|
|School:||Washington State University|
|School Location:||United States -- Washington|
|Source:||DAI-B 82/3(E), Dissertation Abstracts International|
|Subjects:||Mechanical engineering, Electrical engineering, Materials science|
|Keywords:||Anode supported cell, Cobalt manganese spinel coatings, Distribution of relaxation times (DRT), Pressurized SOFC, Solid oxide fuel cell, Time domain impedance spectroscopy|
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