Economic assessment of a solid oxide fuel cell system for biogas utilization in sewage plants

Fuel cells are likely to make their market introduction through high-efficiency applications in niche markets. A possible market for SOFC systems is therefore the utilization of biogas from sewage treatment plants. However, the feasibility of fuel cell applications crucially depends on the gas cleaning system. A system layout for SOFC integration is derived from an existing fuel cell system for biogas utilization, providing a feasible design for gas cleaning for contaminant removal and data on different operation regimes. The resulting SOFC plant provides electricity and heat for on-site usage at the sewage plant by cogeneration. The SOFC system is then analyzed at system level regarding its economic viability compared to a conventional CHP system. Costing for the different system components is made using cost data and literature-based estimates. Different design studies concerning system size and a subsequent sensitivity study concerning decisive economic parameters are used to provide robust decision measures. The study shows that economic feasibility of an SOFC system for biogas utilization can be achieved without subsidies in the near future if SOFC system prices are reduced from 7000 to about 3000 EUR/kWel. It is further shown that smaller SOFC systems are preferable due to their current economies of scale.