Analysis of the performances of a solid oxide fuel cell fed by biogas in different plant configurations: An integrated experimental and simulative approach

Solid Oxide Fuel Cells (SOFC) are efficient, modular and fuel-flexible high temperature electrochemical devices. SOFC systems can be coupled to biogas from anaerobic digestion plants to obtain efficient and decentralized CHP systems, maximizing the valorization of biogas in virtuous waste-to-energy schemes. The main challenges for biogas-SOFC plants are related to performance stability and degradation at process level. In this work the performance and stability of an electrolyte supported SOFC single cell (100 cm2) fed with biogas mixtures derived from different integrated biogas-SOFC CHP plant configurations (hot/cold recirculation; UFf 65–85% - obtained from previous simulation work) has been analyzed with an integrated experimental and simulative approach. To support the experimental results, a chemical equilibrium model of the gas conversion processes coupled with the electrochemical conversion route is developed in MATLAB in order to simulate the gas composition at the anode outlet, which is compared and validated with experimental data obtained by Gas Chromatography (GC). Results show that suitable and stable cell performances are obtained while feeding the SOFC samples by biogas (720–800 mV; 0.16–0.2 W/cm2 at 0.25 A/cm2) where the main performance losses are related to steam content - as well as other gas species, deriving from the pre-processing of the biogas. The gas composition and UFf simulation results show good correspondence with the GC data (error range <5% for the matrix gases and <10% for water) highlighting that the SOFC processes under clean biogas can be successfully represented - to a certain extent - by a chemical equilibrium model.