A 2-D model for Intermediate Temperature Solid Oxide Fuel Cells Preliminarily Validated on Local Values

Abstract

Intermediate Temperature Solid Oxide Fuel Cell (IT-SOFC) technology offers interesting opportunities in the panorama of a larger penetration of renewable and distributed power generation, namely high electrical efficiency at manageable scales for both remote and industrial applications. In order to optimize the performance and the operating conditions of such a pre-commercial technology, an effective synergy between experimentation and simulation is fundamental. For this purpose, starting from the SIMFC (SIMulation of Fuel Cells) code set-up and successfully validated for Molten Carbonate Fuel Cells, a new version of the code has been developed for IT-SOFCs. The new release of the code allows the calculation of the maps of the main electrical, chemical, and physical parameters on the cell plane of planar IT-SOFCs fed in co-flow. A semi-empirical kinetic formulation has been set-up, identifying the related parameters thanks to a devoted series of experiments, and integrated in SIMFC. Thanks to a multi-sampling innovative experimental apparatus the simultaneous measurement of temperature and gas composition on the cell plane was possible, so that a preliminary validation of the model on local values was carried out. A good agreement between experimental and simulated data was achieved in terms of cell voltages and local temperatures, but also, for the first time, in terms of local concentration on the cell plane, encouraging further developments. This numerical tool is proposed for a better interpretation of the phenomena occurring in IT-SOFCs and a consequential optimization of their performance.

A New Model for Constant Fuel Utilization and Constant Fuel Flow in Fuel Cells

“…Figures 8 and 9 use E Nernst = 1 V and r = 3.28125 × 10 −3 Ω. Results of model validation are shown in Figure 10, where the experimental polarization data (on a planar single SOFC at ENEA laboratories) were graphically obtained from Reference [61]. The results show reasonably good agreement, with an average absolute relative error of 3.96%.…”

“…Two-dimensional (2-D) models (e.g., [59][60][61]) consider a two-dimensional cross-section of the cell geometry, ignoring the variations along the third dimension.…”

“…Semi-empirical models (e.g., [61,75]) employ a mix of theory and experimentation. The line between the theoretical and the semi-empirical is sometimes blurred.…”

“…Since the experimental current reported in Figures 9 and 10 of Reference [87] starts at 87 A for Test 1018, the Nernst voltage was estimated, by an approximate extrapolation (as in Figure 7-17 of Reference [85]), to be 0.74 V. The temperature was 1273 K, and the cell area was 870 cm 2 [87]. The resistance was estimated (following Reference [61]), from the slope of the (approximately) linear part of the experimental polarization (current-voltage) curve, to be 0.0006 Ω. The slope was obtained from the equation of the straight line derived by a least-squares linear regression fit of all but the first five experimental data points.…”

“…The results show reasonably good agreement, with an average absolute relative error of 3.96%. The validation was done under the following operational condition [61] for both the model and the experiment: temperature: 923 K; pressure: atmospheric; q in H2 : 0.00112 mol/s; q in O2 : 0.00038 mol/s; anode: 96% hydrogen, 4% water; cathode: 21% oxygen, 79% nitrogen; cell area: 121 cm 2 . The calculated value of the model E Nernst was 1.122 V, with the value of E 0 in Equation (2) estimated from the following relationship [61,95,96]:…”