Design point, part load and annual performance analysis of a 100 kW SOEC system integrating a solar steamer under electrolyser operational constraints

This work presents a numerical analysis and optimization of a modular 100 kWe Solid Oxide Electrolyser (SOEC) system integrated with a solar steamer. The study considers the electrolyser operation constraints and quantifies the impact on relevant Key Performance Indicators (KPI). A process flow diagram of the SOEC system is used, and the air flow rate (sweep gas) is optimized, ensuring that SOEC constraints and KPI targets are met. Four SOEC operational modes are analysed: full load, partial load, hot standby and night mode. Subsequently, the 100 kWe SOEC module, composed of four stack units of 25 kWe, is integrated with a concentrated solar thermal (CST) system that generates the solar steam. The CST system is located in Seville, Spain. It is found that an air mass flow rate of 112 kg h−1 for the large 100 kWe SOEC module ensures that all the constraints imposed by the SOEC are met and KPI targets are achieved. In particular, the hydrogen production is 2.73 kg h−1, with a power-to-hydrogen energy conversion efficiency of 86.2 %, 38.7 kWhe/kgH2, and the annual fraction of hours in which the SOEC has been driven by solar steam of 53.2 % for full-operation mode.