Thermo-electrochemical modelling of high temperature methanol-fuelled solid oxide fuel cells

Abstract

Methanol is a promising fuel for the solid oxide fuel cell (SOFC) due to its easy storage and transportation compared with hydrogen. As no thermo-electrochemical modelling study has been conducted on methanol-fuelled SOFC, a 2D model is developed to simulate the methanol decomposition reaction, water gas shift reaction, electrochemical reactions, heat and mass transfer processes in the methanol-fuelled SOFC. After model validation, parametric simulations are performed to investigate the effects of the operating potential, steam to carbon ratio, the inlet temperature and fuel/air flow rates on the performance of SOFCs. At 1073 K, the peak power density of methanol-fuelled SOFC is higher than 10000 W m−2 with the steam to carbon ratio of 1. In addition, the temperature distribution in SOFC could be remarkably affected by the working conditions due to the chemical/electrochemical reactions and overpotential losses. Large temperature variation (nearly 180 K) between the inlet and outlet of the SOFC is observed mainly due to greatly improved current density at low operating potential. Also, temperature reduction can be achieved by increasing the steam to carbon ratio and gas flow rates (higher than 170 SCCM for air and 0.1 ml min−1 for fuel mixture, respectively), which could improve the long-term stability from the perspective of the thermal stress but inevitably lower the efficiency of the SOFC. Meanwhile, higher inlet temperature not only enhances the power output, but improves the uniformity of the cell temperature distribution. Overall, the investigations of the present study could serve as a solid guidance to understand the thermal characteristics of solid oxide fuel cells running on mixture of the steam and methanol.