Planar Solid Oxide Electrolysis Cell Research Articles

Numerical simulation of flow channel geometries optimization for the planar solid oxide electrolysis cell

In a solid oxide electrolysis cell (SOEC), the flow channel design influences the gas distribution, mass transfer, temperature distribution, and electrochemical properties significantly. This study evaluates the overall performance of SOECs with rectangular, triangular, trapezoidal, and semicircular flow channels and examines the effect of the geometry of the flow channel cross-section on the electrolysis process, gas flow, and material distribution. The trapezoidal flow channel shows the best electrochemical performance, but requires a high power and high pressure drop; the triangular flow channel has the most uniform gas velocity and distribution; and the semicircular flow channel shows the maximum gas velocity. The trapezoidal shape is found to be the optimal shape. Sensitivity analysis of the SOEC with the trapezoidal flow channel indicates that increasing the operating temperature improves the electrochemical performance, and reducing the inlet gas's steam volume fraction increases the gas conversion rate and decreases the electrolysis voltage.

A Parametric Study on the Interconnector of Solid Oxide Electrolysis Cells for Co-Electrolysis of Water and Carbon Dioxide

The shipping industry is trying to use new types of fuels to meet strict pollutant emission regulations and carbon emission reduction targets. Hydrogen is one of the options for alternative fuels used in marine applications. Solid oxide electrolysis cell (SOEC) technology can be used for hydrogen production. When water and carbon dioxide are provided to SOECs, hydrogen and carbon monoxide are produced. The interconnector of SOECs plays a vital role in cell performance. In this study, a 3D mathematical model of cathode-supported planar SOECs is developed to investigate the effect of interconnector rib width on the co-electrolysis of water and carbon dioxide in the cell. The model validation is carried out by comparing the numerical results with experimental data in terms of a polarization curve. The rib width is varied from 0.2 mm to 0.8 mm with an interval of 0.1 mm. It is found that the cell voltage is decreased and then increased as the rib width increases. When the current density is 1 A/cm2, the voltages of SOECs with rib widths of 0.2 mm, 0.6 mm, and 0.8 mm are 1.272 V, 1.213 V, and 1.221 V, respectively. This demonstrates that the best performance is provided by the SOEC with a rib width of 0.6 mm. In addition, the local transport processes of SOECs with different rib widths are presented and compared in detail. This study can provide guidelines for the design of interconnectors of SOECs.

Numerical simulation and analysis of the thermal stresses of a planar solid oxide electrolysis cell

ABSTRACT Hydrogen production using solid oxide electrolysis cells (SOECs) is a highly efficient and low-carbon pathway to generate high purity hydrogen. However, high working temperatures may result in high thermal stress due to a mismatch in the coefficient of thermal expansion (CTE) between components with a nonuniform temperature distribution. Serious stress concentration may lead to structural failure of the SOEC stack. Hence, this work investigated the thermal stress of SOECs through a three-dimensional planar SOEC unit model. A stress analysis method was proposed via a multi-physics coupling model of SOECs using Comsol Multiphysics software. The impacts of voltage, flow direction, water mole fraction, and operating pressure on the thermal stress were evaluated. Numerical results show that the highest maximum principal stress is located in the electrolyte in the SOEC unit. Raising the water mole fraction and the CTE of the electrolyte could reduce the thermal stress if the voltage is below the thermoneutral voltage.

Numerical investigation of solid oxide electrolysis cells for hydrogen production applied with different continuity expressions

A dynamic SOEC (Solid Oxide Electrolysis Cell) model is proposed to investigate the transient response and steady performance of a planar SOEC. Three representative types of continuity equation expressions are systematically compared for the simulation of source terms introduced by electrochemical reactions. For the conservative form of continuity equation (Type A), reasonable predictions at both sides of cathode and anode cannot be achieved, as the diffusion effect is neglected. The non-conservative form of continuity equation (Type B) can obtain reasonable prediction for the cathode side but poor prediction for the anode side. The Type C of continuity equation, newly proposed by the authors for modeling the SOECs, is based on the law of volume conservation. It could achieve the volume increment (oxygen produced) at the anode compartment and good agreements with the analytical ones. It is also found that continuity equations significantly influence the fluid flow and mass transport, whereas their effects on the electrical characteristics are negligible when the global current density is not high.

Computational fluid dynamics approach for performance evaluation of a solid oxide electrolysis cell for hydrogen production

A finite volume method based computational fluid dynamics model has been developed and applied for a cathode-supported planar solid oxide electrolysis cell (SOEC) operating in cross-flow configuration arrangement. The performance behavior, in terms of current density, temperature distribution and hydrogen production in an SOEC, has been investigated for different operating voltages and compared with a corresponding parallel-flow configuration. The predicted results show that higher current densities are obtained for higher operating voltages. The anodic current density is higher than the cathodic one. Yet, the parallel-flow configuration yields lower current density values although they remain in the same order of magnitude as those from the cross-flow arrangement. The simulation reveals various temperature profiles depending on the operating voltage emphasizing the three thermal operating modes of an SOEC, i.e., endothermic, thermo-neutral and exothermic. Per contra, the parallel-flow arrangement gives a temperature decrease along the flow direction although operating in exothermic mode. Higher hydrogen molar fractions at the outlet of the cathode channel were obtained at higher operating voltages due to the higher current densities generated and the exothermic operating mode. The parallel-flow arrangement yields lower hydrogen production due to the lower current densities revealed.

Performance Analysis of Solid Oxide Electrolysis Cells for Syngas Production

There is a significant effect from operating parameters on solid oxide electrolysis cell (SOEC) performance. The object of this research is to simulate the complex phenomena inside a planar SOEC in order to identify the best operating conditions. The model involves an intermediate fidelity of the electrochemical and thermo-fluid phenomena inside the cell. An example of the model validation for an electrolyte supported SOEC is presented here. The model is then employed to investigate various parameters such as temperature, fuel composition, flow rates and H2/CO ratio related to SOEC performance as well as hydrogen and syngas production. It has been observed that the reversible water-gas-shift (rWGS) reaction plays an important rule inside the fuel channels. Although the operating temperature, fuel composition and flow rates have direct effect on SOEC performance and power consumption, their influence on rWGS is more significant.

Polarization Loss of Single Solid Oxide Electrolysis Cells and Microstructural Optimization of the Cathode

High temperature steam electrolysis(HTSE),which is the electrolysis of steam at high temperature with high efficiency using planar solid oxide electrolysis cell(SOEC) technology,has received an increasing amount of international interest because of its potential for large-scale hydrogen production using nuclear hydrogen in future.However,it is of great importance to control polarization energy loss and performance degradation for a practical HTSE process.In this paper,the distributions of the polarization resistances of the LSM/YSZ/Ni-YSZ(LSM:Sr doped LaMnO3;YSZ:Y2O3 stabilized ZrO2) cell under a real operating state and using different operating modes were investigated by electrochemical impedance spectroscopy(EIS).We discussed the differences between the SOEC and the solid oxide fuel cell(SOFC) while the steam diffusion process in the cathode support layer of SOEC was determined to be the rate-determining step.Based on the above-mentioned research,the microstructure of the cathode support layer was adjusted and optimized by polymethyl methacrylate(PMMA) pore formers.The results show that the SOEC cell gives much better performance after the optimization.The porosity increased by 50% when PMMA was used.The hydrogen production rate was as high as 328.1 mL·cm-2?h-1(nominal) when using an electrolysis voltage of 1.3 V,which was about 2 times as that of the starch pore formers.The cell was operated stably for more than 50 h.Our research provides theoretical data and establishes a technical foundation for further study into and application of this novel technology.

Preparation and Electrochemical Performance of Hydrogen Electrode and Electrolyte for SOEC by Tape Casting and Lamination

The solid oxide electrolysis cell (SOEC) has been receiving increasing research and attention worldwide due to its potential usage for large-scale production of hydrogen. Tape casting and lamination technique were successfully used to fabricate the NiO-YSZ hydrogen electrode substrate cermets of planar solid oxide electrolysis cell. In this paper the green tape with thickness of 350μm was prepared by tape casting and then the lamination was used to obtain the required thickness for the NiO-YSZ hydrogen electrode-supported electrolyte cermets. The rheological properties of the suspensions with NiO-YSZ and YSZ were studied, respectively. The optimal temperature and pressure of the lamination were determined, and four direction of lamination mode was used according to tape casting direction to obtain symmetrical and even hydrogen electrode-supported electrolyte after co-sintering. Pore-formers were used to increase the porosity of the hydrogen electrode. The green tape was analyzed by TG-DSC analysis, the microstructure was observed by scanning electron microscope. The electrochemical performance of unit cell was measured at 850°C.

Computational Fluid Dynamics Model of a Planar Solid-Oxide Electrolysis Cell for Hydrogen Production from Nuclear Energy

A three-dimensional computational fluid dynamics (CFD) model has been 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 an electrolysis stack. Details of the model geometry are specific to a stack tested at the Idaho National Laboratory (INL). Mass, momentum, energy, and species conservation and transport are provided via the core features of the commercial CFD code FLUENT. 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 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 in a range of stack operating conditions. Mean model results are shown to compare favorably with experimental results obtained from an actual ten-cell stack tested at INL.

平板型固体酸化物セルによる高温水蒸気電解システムの電気分解効率

平板型固体酸化物セルによる高温水蒸気電解システムの電気分解効率