Development and Optimization of a Solid Oxide Fuel Cell Gas Turbine Hybrid System

Solid Oxide Fuel Cells (SOFC) are an advanced form of fuel cells which can convert hydrocarbon-based fuels into electricity at efficiencies reaching 60%. Fuel efficiency may be increased to 70% or higher by closely integrating a SOFC into the hot gas path of a Brayton cycle gas turbine. SOFCs, unlike more common low temperature fuel cell technologies such as PEM, operate at elevated temperatures between 500°C and 1,000°C, temperatures well suited for integration with turbomachinery. Fuel efficiency is enhanced through several mechanisms including: (1) operating the SOFC at elevated pressure, (2) by tightly integrating the SOFC between the gas turbine’s compressor and expander, (3) by using the gas turbine’s combustor to oxidize dilute fuel in the anode tail gas further heating the already hot and pressurized cathode tail gas before expanding it through a turbine to create additional power, and (4) by eliminating much of the parasitic balance-of-plant (BOP) required to preheat and circulate air through the SOFC. The authors are part of a multi-company collaboration to develop and demonstrate a SOFC/GT system with unique elements such as an integrated cathode recuperator and a fuel to AC electrical conversion efficiency exceeding 70%. This paper covers the system’s development with a specific focus on tradeoffs and optimizations throughout the system design.