Analysis of performance optimization of high‐temperature solid oxide electrolytic cell based on the coupling of flow, heat, and mass transfer and electrochemistry

Abstract

A three‐dimensional (3D) model simulating the flow, heat, and mass transfer characteristics of a high‐temperature solid oxide electrolytic cell (SOEC) is developed based on the coupling of gas flow in channels, the electrochemical reaction in the triple‐phase boundary of electrodes and component diffusion in the porous media in electrodes. The model comprises several equations such as mass equation, momentum equation, energy equation, mass transport equation, and electrochemical reaction equation. The computational fluid dynamics method is adopted to simulate the operating performance (current density distribution, temperature distribution, and gas component distribution) of the 3D electrolytic cell model under different operating conditions (electrolytic voltage, gas temperature at the inlet, flow rate and flow pattern). The simulation results show that gas temperature at the inlet obviously influences electrolytic hydrogen production by SOEC. In the case of lower voltage, a higher temperature can be selected to effectively increase the current density. When the current density is high enough, the supply flow of water vapor needs to be increased to prevent the inhibition reaction of low‐concentration reactants, but this may lead to the reduction of water vapor conversion. In practical operation, a lower voltage and higher gas temperature should be selected, and the flow rate of water vapor appropriately increased to ensure hydrogen production and improve operating efficiency.

High Temperature Solid Oxide Electrolysis – Technology and Modeling

“…Another variation with respect to how the electrochemical reaction is implemented in the models, is the location assumed for the charge transfer to take place. In order to reduce implementation and computational effort, many models position the electrochemical charge transfer reaction at the interface between electrolyte and electrode and implement it as an interface condition [39,50,51,55,60,[76][77][78][79][80][81][82][83][84][85][86]. This simplified picture can be enhanced by assuming the charge transfer to be homogeneously distributed in the electrode in combination with a model to determine TPB density [58,[87][88][89][90], an approach that increases the complexity of the model and demands for a finer spatial resolution of the electrode.…”

“…To cover both the impact of the alternating ribs and gas channels and the varying conditions along the gas channel, the modeled geometry needs to be extended to a 3D channel RPU [53,57,59,84,91,92,122,140,142,147,195]. The species distribution in the electrodes in contacted areas along the gas channel is investigated for isothermal [53,122,147] and non-isothermal conditions [57,143].…”

“…The species distribution in the electrodes in contacted areas along the gas channel is investigated for isothermal 53, 122, 147 and non‐isothermal conditions 57, 143. Additionally, in non‐isothermal models, current density 57, 143, overpotentials 57 and temperature distributions 57, 84, 142, 143, 195 are resolved for the entire electrodes, including the areas under ribs. Further, modeling the channel in 3D allows for the examination of crossflow configuration for single channels 122, 143, 147.…”

Manipulating and Optimizing the Hierarchically Porous Electrode Structures for Rapid Mass Transport in Solid Oxide Cells

“…[3] The material structure, porosity, tortuosity factor (τ), and other factors have a direct impact on the mass transfer effect, and further affect the performance of the material or device. [4][5][6][7] The tortuosity factor is one of the important parameters reflecting the mass transfer effect in porous materials. [2,8] The tortuosity factor of a conducting medium (solid phase for charge transport or pore phase for gas diffusion) is defined as…”

“…[ 3 ] The material structure, porosity, tortuosity factor (τ), and other factors have a direct impact on the mass transfer effect, and further affect the performance of the material or device. [ 4–7 ] The tortuosity factor is one of the important parameters reflecting the mass transfer effect in porous materials. [ 2,8 ] The tortuosity factor of a conducting medium (solid phase for charge transport or pore phase for gas diffusion) is defined as $$\tau = \frac{{\phi {\sigma _{\rm{o}}}}}{{{\sigma _{{\rm{eff}}}}}}$$, where ϕ represents the volume fraction of conducting medium, σ 0 is the conductivity or diffusivity of the pure conducting medium, and σ eff is the effective conductivity or diffusivity of the porous medium.…”