Solid oxide fuel cell systems in hydrogen-based energy storage applications: Performance assessment in case of anode recirculation

The application of solid oxide technology as a reversible system to renewable energy storage puts the attention on its operation and optimization under hydrogen feeding. To this aim, the effect of the anodic off-gas recirculation on the performance of a solid oxide fuel cell (SOFC) system fuelled with hydrogen is investigated. The layout presented includes the recirculation of anodic exhausts according to a variable rate, the condensation of the steam in the recirculated flow and the regeneration of the feeding flows. The operating parameters set in the 0-D developed model came from a test campaign aimed at determining SOFC performances varying the fuel utilization factor (Uf) and current density. In order to find the highest efficiency values, both fuel utilization factor and anode recirculation flow rate have been varied. Simulations results show the favorable effect on the system electrical efficiency for low utilization factor when operating with high anodic recirculate rates. With recirculation rates over 80 %, set the produced power, higher system energy conversion efficiencies up to 68.6 % are exhibited with lower cell Uf (down to 0.2). This design allows SOFC to overperform the best PEM performance recorded in literature.