Results from an industrial size biogas-fed SOFC plant (the DEMOSOFC project)

The EU-funded DEMOSOFC project aims to demonstrate the technical and economic feasibility of operating a 174 kW_e Solid Oxide Fuel Cell (SOFC) in a wastewater treatment plant. The fuel for the three SOFC modules (3 × 58 kW_e) is biogas, which is available on-site from the anaerobic digestion of sludge collected from treated wastewater. The integrated biogas-SOFC plant includes three main units: 1) the biogas cleaning and compression section, 2) the three SOFC power modules, and 3) the heat recovery loop. Main advantages of the proposed layout are the net electric efficiency of the SOFC, which is in the range 50–55%, and the near-zero emissions. A specific focus of the demonstration project is the deep and reliable removal of harmful biogas contaminants. The presented work is related to the design of the SOFC system integrated into the wastewater treatment plant, followed by the analysis of the first results from the plant operation. We analyzed the biogas yearly profile to determine the optimal SOFC capacity to install that is 3 SOFC modules. The rational is to maintain high the capacity factor while minimizing the number of shutdown per year (due to biogas unavailability). First results from plant operation are also presented. The first SOFC module was activated in October 2017 and the second in October 2018. The measured SOFC efficiency from compressed biogas to AC power has always been higher than 50–52%, with peaks of 56%. Dedicated emissions measurements have been performed onsite during December 2017. Results on real biogas operation show NO_x < 20 mg/m³, SO₂ < 8 mg/m³ (detection limits for the instrument) and PM lower than ambient air values.