Means to Improve Fuel Cell Aircraft Performance through Hybridization and Design Mission Constraints

The electrification of general aviation serves as the entry-point to making the aviation industry carbon neutral as a whole. The low power requirement and fuel demand of general aviation aircraft makes this segment suitable to explore various configurations of electrical powertrains. Many concepts and retrofit studies of existing aircraft with battery- or fuel cell-electric power source have been developed in the past decade, but these concepts usually result in limited range and performance. One solution to increase the aircraft range is to use the combination of fuel cells and batteries in a hybrid-electric configuration and to optimize the load sharing between them. In the present study, a simulation model is developed that represents the forces acting on the aircraft as well as the two energy systems, i.e. battery and fuel cell. With this model, critical flight segments such as takeoff and climb-out are analyzed to identify principal design requirements, while considering certification criteria and environmental conditions. A Cessna 400 aircraft is used as a reference. For this aircraft it is demonstrated how to overcome some of the performance limitations due to electrification by developing a power split strategy that leverages the advantage in terms of energy density and flexibility, respectively. The results demonstrate how an adjusted trajectory can reduce the power train weight and therefore keep payload reduction at a minimum.