Eccentric elliptical cone groove anode design for SOFCs: trade-offs between the cell's power density increment and the imposed thermal gradients

This study develops a novel three-dimensional planar SOFC model through a tailored design of the anode support layer with an eccentric conical groove. Four geometric parameters-the ellipse's grooving depth h, the long semi-axis a, scaling ratios k, and the centers distance w-was optimized to slow down the thermal gradient while increasing the current density. The presence of elliptical grooves significantly accelerates the gas flow rate entering the electrolyte, and thus leads to a more robust electrochemical reaction and heat dissipation. Thereby, the maximum cell power increases substantially by 44.09 % from 28,977.37 W/m2 to 41,754 W/m2, due to improvement in the Ohm's and concentration polarization (the equilibrium potential Eeq > 0.5 V) at low operating voltages below 0.6 V. The increment in the power density is further evaluated through the hydrogen conversion rate, velocity configurations, and Damköhler number (Da, ratio of chemical reaction to mass diffusion rate) along the slot depths for different h, w, and k, which provides insights into the enhanced mass transfer and chemical reactions. However, the introduction of grooves amplifies local temperature gradients (increasing from 196 K/cm to 439 K/cm), the gradient can be reduced to 281 K/cm by either adjusting the long semi-axis a or expanding the distance w, disrupting the thermal boundary layer thickness to enhance gas convective heat transfer. That is a 36 % improvement relative to the worst-case scenario, yet still 43 % higher than the baseline. This trade-off necessitates advanced thermal management in high efficiency SOFCs.