Performance Models for Zirconia Electrolyte Cells at Low Current Density

Abstract

This preliminary design study compares high temperature electrolysis, having H20(g) flow delivered parallel to the tube (model I), with H20(g) reactant cross-fed, perpendicular to the axes of series-connected tubes (model 2). Calculations for model 1 correlate with relevant experimental data. Model 2 calculations predict higher energy efficiencies than model i. If model 2 design philosophy is employed, hydrogen production is estimated, at 99.9% purity, and at i00 mA/cm ~, to require 1.017V at 0.902 energy efficiency, using tubular cells employing the present design. Tube design optimization, with normalized cell resistance, p lowered to 0.35 ~ cm 2, is estimated to result in 99.9% pure hydrogen product at 0.952V and 0.963 energy efficiency for the same i00 mAJcm 2 design point. Hydrogen purity, cell current density, and resistance are key modeling parameters.An electrical generator employing a low temperature trolyte (e.g., 1000~ will provide a net power output (Pnet) hydrogen-oxygen fuel cell in closed cycle with a high if sustaining solar thermal energy is available and cell temperature H20 electrolysis cell with solid oxide eleccurrent effieiencies, ~'f and ~'e are high. If V~ and Ve are, respectively, fuel cell and electrolysis cell driving volt-*Electrochemical Society Active Member. ages, then, at a current, I ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 130.179.16.201 Downloaded on 2015-06-14 to IP Vol. 135, No. 1 ZIRCONIA ELECTROLYTE CELLS 7 P.~t = [c~'fV~ -VJ~'~]I ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 130.179.16.201 Downloaded on 2015-06-14 to IP