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

• Published in: Energy conversion and management Vol. 149; pp. 646 - 659
• Main Authors: Zhang, Ji-Hao, Lei, Li-Bin, Liu, Di, Zhao, Fu-Yun, Chen, Fanglin, Wang, Han-Qing
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.10.2017; Elsevier Science Ltd
• Subjects: Anode effect; anodes; Cathodes; Chemical reactions; Computational fluid dynamics; Computational fluid dynamics (CFD); Computer simulation; Continuity equation; Current densities; Diffusion effects; electrical properties; Electrochemistry; Electrolysis; Electrolytic cells; equations; Fluid flow; Hydrogen; Hydrogen production; mass transfer; Mass transport; Mathematical models; Numerical analysis; oxygen; prediction; SOECs modeling; Source imbalance; Studies; SOECs modeling; Source imbalance; Current densities; Computational fluid dynamics (CFD)
• ISSN: 0196-8904; 1879-2227
• DOI: 10.1016/j.enconman.2017.07.013

•Continuity expressions developed for electrochemical reaction sources.•Diffusion effect could not be neglected in the continuity expressions.•Volume increments could be achieved by the proposed continuity equation.•The continuity equations influenced flow field and electrical characteristics.•Transient solution procedures are developed for modeling the SOECs. 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.