Approaches for Optimum Thermal Management of SOFC Cells: Fitting Operating Conditions & Smart Cell Design

Abstract

The thrust of green hydrogen as energy vector for the consolidation of a net-zero emitting global energy system implies the necessity of a fast development of high performing and highly efficient fuel cells and electrolyzers. Among the commercial choices, solid oxide cells can be considered as a better performing alternative compared to commercial proton exchange membrane and alkaline technologies. The benefits of this kind of technology arise from their higher operating temperatures of around 700-900 ºC, which results in improved kinetics and favored thermodynamics, allowing to reach unrivaled conversion efficiencies and reduced electricity consumption. Furthermore, this allows operating the cell reversibly in both fuel cell (SOFC) and electrolysis (SOE) modes.However, cell overheating and non-uniform temperature distribution can lead to an acceleration of degradation processes and cell cracking and sintering, which challenges long-term cell stability. In this sense, modeling at cell level enables to optimize operating conditions, improve cell design and predict and minimize such phenomena. Simulations allow mimicking the response of the cells and stacks at diverse operating scenarios and accelerates the optimization process minimizing experimental efforts; saving materials, time, and economical resources. We model SOFC/SOE cell behavior by means of Computational Fluid Dynamics (CFD), solving the mass, species, momentum, energy and current conservation equations, as well as electrochemical reaction models.In this work, a detailed methodology to guide design of the thermal management of SOFC by means of CFD and numerical optimization tools is proposed. These approaches combine acting both on operating conditions and cell geometry. Initially, we study the influence of inlet gas flows and describe a procedure to optimize the flows while maximizing the energetic outcome. Afterwards, we describe how numerical methods can allow fitting feed gas temperatures to avoid overheating. Finally, we go a step further by optimizing cell interconnect plate geometries to minimize internal temperature gradients. All in all, we demonstrate how CFD studies can accelerate SOFC cell design in order to maximize performance and extend lifespan. Figure 1