Control of a Solid Oxide Electrolysis system for hydrogen generation from solar power and thermal energy storage

To take advantage of the benefits related to high-temperature Solid Oxide Electrolysis (SOE) systems for hydrogen production with renewable and low-cost electricity and heat, the EU project Prometeo studies the integration of a SOE system with a CSP plant via thermal energy storage. The system will be tested in relevant environment for three different power-to-gas applications. Identified the layout of the 25 kWe pilot system built within the project and the required system operating modes, this work aims at proposing an effective system control strategy. An experimental campaign on a 5 kWe stack has been performed at FBK facility, to find out which parameters mainly affects the hydrogen generation. Experimental results have shown that, with low steam flow rates, the stack current and flowrate of produced hydrogen mainly depend on the steam flowrate, while it is not affected by the stack temperature; conversely, with high steam flowrates, the current depends only on the stack temperature. According to these results, two control strategies are here proposed to be implemented and tested on the Prometeo prototype, being the basis for a further development of the control logic architecture and contributing to the optimization of the system performance.