Solid Oxide Cells systems (SOCs) are increasingly being considered as an electrical energy storage method and therefore as a means to boost the penetration of Renewable Energy and to improve the grid flexibility by power-to-gas electrochemical conversion. However, temperature and reactant utilization control become crucial if the systems are to be used in dynamic operation with intermittent electrical power sources. In the present work, two 1D models of SOC stacks are built and used to study the dynamic behaviour of such stacks, and to select and tune the best control systems. After having compared with literature the accuracy of the models, safe operating ranges are determined to respect the thermal constraints of the stack. The dynamic analysis points out that inputs (m_fuel, m_atr) and outputs (U, ΔT max) are strongly decoupled; therefore, proportionalintegral control strategy has a good potential to prevent dangerous operating conditions in dynamic operation. Finally, the controllers are tuned and their transfer functions are reported.
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Using catalytic supercritical water gasification (CSCWG) in generating energy from wet biomass is efficient and environmentally friendly. However, one of the main challenges in using CSCWG is the low syngas yield and low heating value. Syngas for power and for synthetic fuel production requires high-purity and a high heating value. In this work, a novel system is proposed which increases the CSCWG syngas heating value and yield and produce electricity using a reversible solid oxide cell (ReSOC). The plant can be used for syngas production, working in electrolyser mode powered by excess renewable electrical energy. Thermodynamic calculations indicate that the energy efficiency of the CSCWG-SOEC is in the order of 72%, in this mode the syngas yield increases around five times and is rich in hydrogen and methane, its composition allows operation within the carbon-free region of the C-H-O diagram. ... Read more