Modeling and performance optimization of a solid oxide electrolysis system for hydrogen production

This article presents electrochemical and thermodynamic modeling and optimization of a high temperature solid oxide electrolysis (SOE) system for hydrogen and oxygen production. High temperature electrolyzers offer the significant advantage of high conversion efficiency compared with low temperature electrolyzers. However, the high operating temperatures limit the SOE utilization to resources where high temperature steam is externally provided, such as in nuclear and concentrated solar power plants. Herein, we report the design and thermodynamic performance of an SOE system at a capacity of 1 MWe, from which various renewable electricity resources can be utilized to produce hydrogen and oxygen from water. In order to investigate the standalone operation and eliminate the need for external heat, the SOE is examined while operating in an exothermic mode, where heat is internally generated, and in an endothermic mode, where heat is provided by electric heaters. Additionally, a network of heat exchangers is optimized to increase the system efficiencies and enable an efficient standalone operation. Thus, the SOE system can be adapted for renewable hydrogen production applications, such as wind and Photovoltaic (PV) farms. The influences of operating conditions on efficiencies, power demand, and exergy destruction rates of the SOE system are assessed, including a case of 15 MPa hydrogen storage. The energy and exergy efficiencies of the SOE system are obtained as 85.15% and 83.41%, respectively. Sensitivity and optimization analyses are also conducted in order to highlight SOE stability and optimum performance.