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Performance and environmental study of a biogas-fuelled solid oxide fuel cell with different reforming approaches
(2018-03-01)
Chatrattanawet, Narissara
;
Saebea, Dang
;
Authayanun, Suthida
;
Arpornwichanop, Amornchai
;
Patcharavorachot, Yaneeporn
In this work, solid oxide fuel cells (SOFCs) using biogas as the fuel with two different reforming approaches, i.e., external and internal reforming, were studied to determine the optimal operation conditions for each approach. Thermodynamic analysis was performed using a flowsheet simulator. The equilibrium gas composition was calculated by minimizing the Gibbs free energy. An electrochemical model that includes three voltage losses (i.e., activation, ohmic, and concentration losses) was used to predict the performance of the SOFCs. The simulation results showed that the reformer in the external reforming SOFC should be operated at a temperature of 973 K, a pressure of 1 atm, and a steam-to-carbon molar ratio of 0.5. In performance analysis, the simulation results indicated that both approaches have the same optimal operating conditions, i.e. a temperature of 1173 K, a pressure of 3 atm, and a current density of 5000 A/m2. Under the same operating conditions, the internal reforming SOFC exhibited better electrical efficiency than that of the external reforming SOFC. Considering the CO<inf>2</inf> and CO emissions, the exhaust gas obtained from the anode side of the internal reforming SOFC contained 7.4% CO<inf>2</inf> and 37.9% CO, which are higher values than those for the external reforming SOFC (1.9% CO<inf>2</inf> and 32.5% CO).
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Electrochemical performance assessment of low-temperature solid oxide fuel cell with YSZ-based and SDC-based electrolytes
(2018-01-01)
Saebea, Dang
;
Authayanun, Suthida
;
Patcharavorachot, Yaneeporn
;
Chatrattanawet, Narissara
;
Arpornwichanop, Amornchai
In this work, solid oxide fuel cells (SOFCs) based on different electrolytes, i.e., the yttria-stabilized zirconia (YSZ) and the samaria-doped ceria (SDC), were investigated to study their performances at low-temperature operation. The predicted performance of both SOFCs was validated with the experimental results. The verified models were implemented to study the impact of operating conditions, i.e., cell temperature, pressure, thicknesses of cathode, anode, and electrolyte, on their performances. The decrease in the operating temperature from intermediate range (800–900 °C) to low range (550–650 °C) has a considerable effect on the performance of the YSZ-based SOFC as conventional type, which dropped from 0.67–1.40 W/cm2 to 0.027–0.13 W/cm2. Under the low operating temperature range, the performance of SDC-based SOFC was superior to that of the YSZ-based SOFC, due to the lower ohmic loss. Nevertheless, the SDC-based SOFC has higher concentration overpotentials than the YSZ-based SOFC. The concentration overpotentials of the SDC-based SOFC can be reduced by the thinner anode and cathode thicknesses. In addition, the SDC-based SOFC at low operating temperature with the pressurized operation could significantly improve its power density, about 20% at 2 bar, which was close to that of YSZ-based SOFC at intermediate temperature of 800 °C.

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