Progress in high-temperature electrolysis for hydrogen production using planar SOFC technology

Abstract

A research program is under way at the Idaho National Laboratory to assess the performance of solid-oxide cells operating in the steam electrolysis mode for hydrogen production over a temperature range of 800 to 900ºC. The research program includes both experimental and modeling activities. Selected results from both activities are presented in this paper. Experimental results were obtained from a ten-cell planar electrolysis stack, fabricated by Ceramatec 1 , Inc. The electrolysis cells are electrolyte-supported, with scandiastabilized zirconia electrolytes (~140 µm thick), nickel-cermet steam/hydrogen electrodes, and manganite air-side electrodes. The metallic interconnect plates are fabricated from ferritic stainless steel. The experiments were performed over a range of steam inlet mole fractions (0.1 -0.6), gas flow rates (1000 -4000 sccm), and current densities (0 to 0.38 A/cm 2 ). Hydrogen production rates up to 90 Normal liters per hour were demonstrated. Stack performance is shown to be dependent on inlet steam flow rate. A three-dimensional computational fluid dynamics (CFD) model was also created to model high-temperature steam electrolysis in a planar solid oxide electrolysis cell (SOEC). The model represents a single cell as it would exist in the experimental electrolysis stack. Mass, momentum, energy, and species conservation and transport are provided via the core features of the commercial CFD code FLUENT 1 . A solid-oxide fuel cell (SOFC) model adds the electrochemical reactions and loss mechanisms and computation of the electric field throughout the cell. The FLUENT SOFC user-defined subroutine was modified for this work to allow for operation in the SOEC mode. Model results provide detailed profiles of temperature, Nernst potential, operating potential, anode-side gas composition, cathode-side gas composition, current density and hydrogen production over a range of stack operating conditions. Mean model results are shown to compare favorably with the experimental results obtained from the ten-cell stack tested at INL.

Modeling of a solid oxide electrolysis cell for carbon dioxide electrolysis

“…Because of its good ionic conductivity at high temperatures (873 -1273K), yttria-stabilized zirconia (YSZ) has been widely used as an electrolyte material in solid oxide fuel cells (SOFCs) for electricity generation and solid oxide electrolysis cells (SOECs) for H 2 generation through steam electrolysis [1][2][3][4][5][6][7][8]. In addition to steam electrolysis, SOECs can also be used for CO 2 electrolysis to generate O 2 [9].…”

“…Although there are some valuable modeling studies on steam electrolysis for H 2 production using SOECs [5][6][7][8], a pertinent modeling or reliable analysis on CO 2 electrolysis is needed to understand the physical-chemical processes in an SOEC used for CO 2 electrolysis. Chan et al [13] developed an electrolyte model for CO 2 electrolysis, however, the important gas transport phenomenon in porous electrodes was not considered.…”

Tritium Barrier Materials and Separation Systems for the NGNP

“…Figure 4 shows a schematic for one possible configuration of the NGNP, and Figure 5 shows the tritium material balance calculated for this configuration using the THYTAN model. In this configuration, a 600 MWt VHTR is used to generate electricity and to provide high-temperature heat to a high-temperature steam electrolysis (HTSE) plant used for making hydrogen [31]. Three heat transfer loops are assumed -a primary loop, a secondary loop, and a tertiary loop.…”

The Effects of Operating Conditions on the Performance of a Solid Oxide Steam Electrolyser: A Model‐Based Study

“…Studies of the experimental operation of SOECs can be found in several publications. Herring et al [12] showed that the stack performance is dependent on the inlet steam flow rate based on the experimental measurement and modelling study 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 F o r P e e r R e v i e w 6 of a 10-cell stack. Schiller et al [11] studied the electrochemical performance of an SOEC, and the structure of the materials at different temperatures and current densities, and tested the durability of the stack.…”

“…Brisse et al [13] paid special attention to the impedance behaviour of the SOEC operated at different temperatures, current densities and steam concentration. All these experimental studies of the SOEC (at the cell level and the stack level) are carried out in a furnace where the temperature is maintained at a constant level, although a temperature distribution within the stack has been reported [12].…”