Fuel Cell operation of SOEC modules for backup power in off-grid plants using renewable energies

Abstract

This thesis aims to analyze and study the operation of a reversible Solid Oxide Cells (rSOC) reactor, a new technology in the hydrogen field which is still under examination by research centers worldwide and promises to be a cutting-edge component for future electrical energy storage plants. The entire work has been conducted in collaboration with the Thermodynamics Technical Institute of the German Aerospace Center (DLR) located in Stuttgart, which is involved in a project that aims to link this type of system to renewable energy sources, in order to store the excess electrical energy produced by offshore wind farms as chemical fuels. In this context, the research center has provided all the technical and theoretical support needed for developing the appropriate strategies of investigation. The main activity firstly addresses the research role and illustrates the operating points that could be used to run the system in Fuel Cell mode, in order to employ the chemical reactions between oxygen and hydrogen to produce power when it is required from the grid, and then how to operate the switch to these steady state points from the high temperature Electrolysis mode duty point, so when the system uses the energy surplus from wind turbines to produce chemical fuels. These transients are conducted while respecting some requirements and limits imposed by the reactor manufacturing company or found through online literary research. Keeping these objectives in mind, a preliminary study has been conducted on parameter sensitivity analysis of the model to gain a clearer vision on the effects of the variables involved, delineating all the relationships between different parameters that are useful to understand for subsequently running some steady-state simulations to find the duty points. These represent a starting point for performing the transient mode, which is the most critical working phase for an SOC reactor because of material degradation caused by temperature gradients and electrochemical reactions. Simulations are ultimately used to define the strategies to adopt in order to operate a MW-scale plant that uses or produces electric energy in the most efficient way, taking into account the reactor's life cycle and operation costs.