Proton exchange membrane fuel cells (PEMFC) not only offer more efficient electrical energy conversion, relative to on-ground/backup turbines but generate by-products useful in aircraft such as heat for ice prevention, deoxygenated air for fire retardation and drinkable water for use on-board. Consequently, several projects (e.g. DLR-H2 Antares and RAPID2000) have successfully tested PEMFC-powered auxiliary unit (APU) for manned/unmanned aircraft. Despite the progress from flying PEMFC-powered small aircraft with 20 kW power output as high as 1 000 m at 100 km/h to 33 kW at 2 558 m, 176 km/h [1-3], durability and reliability remain key challenges. This review reports on the inadequate understanding of behaviour of PEMFC under aeronautic conditions and the lack of predictive methods conducive for aircraft that provide real-time information on the State of Health of PEMFCs. Highlights: The main research findings are -To minimize performance loss due to high altitude and inclination by adjusting cathode stoichiometric ratio. -To improve quality of oxygen-depleted air by controlling operating temperature and stoichiometric ratio. -Need to devise real time prediction methods conducive for determining PEMFC SoH in aircraft.
The deployment of proton exchange membrane fuel cell (PEMFC) for aeronautic applications is a value-added energy supply alternative that not only generates useful byproducts (oxygen-depleted air, water and heat) but addresses sensitive issues such as improving health conditions of airport personnel (silent operation minimizes noise) and decreasing greenhouse gas emission (in situ zero emissions). However, the PEMFC is yet to be industrialized due to its fast degrading components. The contribution of the several start-ups and shutdowns (a PEMFC undergoes when operated in aircraft) to the degradation is not well-understood. Hence, this study seeks to explore the effects of start-up/shutdown (SU/SD) cycling on a PEMFC's lifetime. The SU/SD cycling is incorporated with heating to 60 °C and cooling to room temperature to mimic real-life temperature changes encountered in an aircraft. The tested membrane electrode assemblies (MEAs) were characterised for performance and evolution of its components to examine the extent and nature of degradation. More than two-thirds loss of electrochemically active surface area (ECSA) of catalyst, Pt particle growth (4.71-6.41 nm) associated with Ostwald ripening and formation of PtO from adsorption of OH − by Pt-M surface were identified to be causes of the observed voltage decay at 0.196 mV h −1 rate. Hence, it is concluded that SU/SD cycling mostly affects the catalytic component of PEMFC in the aeronautic environment.
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