Effect of Oxygen Diffusion Constraints on the Performance of Planar Solid Oxide Fuel Cells for Variable Oxygen Concentration

Abstract

Performance enhancement of solid oxide fuel cell (SOFC) has been a very prominent research problem of the present era. One of the key performance-limiting factors is diffusional constraint encountered in SOFC cathodes during operation with air. While attempts at improving cell performance have been made through the optimization of geometries, flow rates, and operating conditions, very few studies have reported the potential for performance enhancement through the optimization of cathode gas composition. The present study takes an experimental as well as theoretical approach to examine the extent to which SOFC performance can be enhanced through alterations in the oxygen concentration of cathode gas (without varying the oxygen molar flow rate). An SOFC is operated for various cathodic oxygen concentrations, and the experimental protocol is simulated using a parametric computational fluid dynamics study. The results depict remarkable nonlinearities in the dependence of cell performance indicators on cathode gas oxygen concentration, which opens up a new dimension for the optimization of cell efficiency, contingent on the availability of oxygen, and the design and operational constraints unique to specific SOFC development ventures.

Perspective—Oxygen-Based Fuel Cell and Reversible Systems for Heavy-Duty Motive and Stationary Applications

“…Today, PEMFCs, SOFCs, and PEMWEs dominate the market and have efficiencies of 53, 45, and 72%, respectively. 12,43,44 Round trip efficiencies of 38 and 32% are much lower than those for batteries (Fig. 1a).…”

“…Oxygen operation increases the efficiency of fuel cells from 53 and 45% to 63 and 56% (bridging period). 12,44 Furthermore, PEMWEs are expected to be displaced by the more efficient R-SOFC (88% in comparison to 72%). 26,43 This change would bring a roundtrip efficiency of 55% for a combination of a PEMFC and the R-SOFC (the oxygen produced by the R-SOFC is in part consumed in a PEMFC) and 77% for the R-SOFC.…”

Techno-Economic Analysis of Solid Oxide Fuel Cell-Gas Turbine Hybrid Systems for Stationary Power Applications Using Renewable Hydrogen

“…The reduced cooling air mass flow leads to an increase of the average PEN temperature (while maintaining the same thermal gradients) accelerating the electrochemical reaction kinetics, especially the oxygen diffusion which is the man resistance. However, at the same time, the lower O 2 concentration on the cathode reduces reaction kinetics at the cathode-electrolyte interface, which leads to a decrease of the oxygen at the anode-electrolyte interface [51]. With concentration effects being slightly more dominant, this leads to a lower current density, and thus, slightly more stacks are needed.…”