Solid Oxide Fuel Cell/Gas Turbine Hybrid APU System for Aerospace Applications

Traditionally, electric generators, driven by an aircraft\´s main propulsion engines or by a gas turbine auxiliary power unit (APU), have supplied the electrical needs of commercial aircraft. In flight, the marginal efficiency of electric power generated by the main engines and their generators is at most 30-40%. While on the ground with the engines shut off, the average fuel efficiency of the turbine powered APU is typically less than 20% and also has undesirable noise and gaseous emissions. As environmental concerns mount, aircraft manufacturers and others are challenged to reduce fuel consumption while simultaneously reducing emissions. Hence, there is very strong interest in developing fuel cells for aerospace applications. This paper reports on the study results of using solid oxide fuel cells (SOFC) in combination with a gas turbine (GT) as a hybrid APU system for a commercial aircraft. The purpose of this feasibility study is to investigate the potential use of fuel cell based APUs for onboard power generation in future "more electric" commercial aircraft. In this paper, the modeling of the major components of the SOFC-GT power generation system, summary of the findings, challenges, and final recommendations are presented