A novel control strategy to neutralize internal heat source within solid oxide electrolysis cell (SOEC) under variable solar power conditions

Abstract

The integration of solid oxide electrolysis cells (SOECs) with a photovoltaic (PV) system presents a viable method of storing variable solar energy through the production of green hydrogen. To ensure the safety and longevity of SOEC amidst dramatic fluctuations in solar power, control strategies are needed to limit temperature gradients and rates of temperature change within the cell. Recognizing that the supply of the reactant influences the current, a novel control strategy is developed to modulate internal heat source in the SOEC by adjusting the steam flow rate. The effectiveness of this strategy is assessed through numerical simulations conducted on a coupled PV-SOEC system using actual solar irradiance data. The irradiance data are recorded at two-second intervals to account for rapid changes in solar exposure. The results indicate that conventional control strategies, which increase airflow rates, are inadequate in effectively suppressing the rate of temperature variation in scenarios of drastic changes in solar power. In contrast, our proposed strategy demonstrates precise management of SOEC internal heat generation, thus reducing the temperature gradient and variation within the cell to less than 5 K cm−1 and 1 K min−1, respectively, and maintaining a high electricity-to-hydrogen conversion efficiency of 94.9%.