Assessing the Impact of Inverter Current-Ripple on SOFC Performance

The effect of inverter ripple current on fuel cell stack performance is not well understood. This paper provides a first-order examination of the impact of inverter load dynamics on SOFC fuel cell operation. Previous work using steady-state fuel cell loading has shown that DC-current loading itself results in degradation of the fuel cell, albeit in ways yet to be fully understood. This result suggests that the varying reactant conditions that result from ripple may modify degradation processes, and, therefore, the lifetime of the cells. This paper investigates these conditions through the use of a dynamic one-dimensional model for the detailed mass transport occurring within the electrode of a cell. In this work, the inverter load is imposed as a boundary condition to the transient model. Results show the behavior of the reactant concentrations within the stack electrodes under inverter loads with frequencies between 60 Hz and 1250 Hz. It is concluded that a ripple factor of less than 6% be used to ensure minor impact to the conditions at the electrode-electrolyte interface.