Fuel Cells as APU in Aircrafts

Abstract

AbstractAn auxiliary power unit (APU) is responsible for powering different aircraft electrical demands, mainly electrical services, when the aircraft is on the ground. Conventional APUs comprise a generator coupled to a combustion engine that partially consumes the aircraft jet fuel, which causes noise and environmental pollution. Aircraft efficiency improvements rely on substituting systems that were once mechanical, pneumatic, and hydraulic to systems in search of higher efficiency, reliability, and reduction of costs and pollutant emissions, such as in a more electric aircraft (MEA). In a fuel cell APU, the combustion engine is replaced by a fuel cell, an electrochemical device producing electrical energy with higher conversion efficiency. A fuel cell generates heat and water on board that can reduce the use of heavy on board aircraft components (e.g., water tanks) and improve passenger satisfaction. After introducing technical details of conventional APUs, this chapter presents current developments of fuel cell APUs. It focuses on the two most promising fuel cell APUs types, the APU comprising a solid oxide fuel cell (SOFC-APU) and a proton-exchange membrane fuel cell (PEMFC-APU).KeywordsAPUFuel cellsSOFCPEMFCMEAElectrified aircraft