Techno-economic analysis of solid oxide fuel cell-based combined heat and power systems for biogas utilization at wastewater treatment facilities

This paper presents a techno-economic analysis of biogas-fueled solid oxide fuel cell (SOFC) systems for combined heat and power (CHP) applications in wastewater treatment facilities (WWTFs). SOFC-CHP systems ranging from 300 kWe to 6 MWe in electric power capacity are explored in terms of their performance and life cycle costs. Representative biogas feedstock is established from compositional data for a large wastewater reclamation facility in Denver, Colorado. A steady-state SOFC-CHP system model is developed with Aspen Plus for the integration with small (640 kWLHV), medium (2.97 MWLHV) and large (11.92 MWLHV) biogas sources. The proposed SOFC system concept includes anode gas recirculation, a biogas pretreatment system, and a waste heat recovery unit. The system offers a net electrical efficiency of 51.6% LHV and a net CHP efficiency of 87.5% LHV. The effect of operating parameters on system efficiency is investigated with a parametric study. The economic performance is evaluated with the levelized costs of electricity (COE) and heat (COH). The results are compared with the COE from reciprocating engine, gas turbine, microturbine, molten carbonate fuel cell technologies, and grid electricity prices. The influence of economic parameters and stack operating parameters on the levelized COE is also presented.

► SOFC systems fueled with biogas offer net electrical efficiencies near 52% (LHV).
► Estimated installed costs range from 3590 $/kW to 5780 $/kW (large- to small-scale).
► SOFC-based cost of electricity is competitive with grid-pricing at 5–8 ¢/kW h.
► SOFCs for biogas applications are competitive with other cogeneration technologies.
► Economic viability also depends on biogas quality, utility pricing, and incentives.