Experimental and simulative design of isothermal high temperature electrolyser controller for coupling with renewable energies

Electrolysis via solid oxide cells (SOC) shows unprecedent high electrical efficiencies, but transient SOC operating capabilities on a system level are still unclear and require the development of adequate control and operating strategies to minimize thermal gradients inside the reactors. In this study, we present an algorithm to maintain isothermal operating conditions in a SOC reactor. This algorithm has been created in an in-house simulation framework using a 24-stack model for different transient operating conditions, tuning the current demand of the reactor based on the fluctuating supply of fuel. Following, the simulation outco mes are validated in the experimental investigation, where the SOC reactor is operated dynamically, simulating a coupling with fluctuating energy sources. In the manuscript, the cardinal equations of the algorithm, and both simulative and experimental results will be shown in detail, eventually leading to a diminished temperature change of the SOC reactor of maximum 10 K. Ultimately, this approach leads to a faster response from SOC reactors in transient conditions, and can potentially drive a more widespread usage of the technology in combination with fluctuating energy sources. Analysis of the results will be presented to showcase a possible coupling between a SOC reactor and a renewable wind and/or PV source.