A Modeling Approach for the Effect of Battery Aging on the Performance of a Hybrid Electric Rotorcraft for Urban Air-Mobility

Abstract

The interest in electric and hybrid electric power systems for aircraft and rotorcraft has been increasing significantly in recent years. However, advanced simulation tools still need to be developed to exploit the potentiality and address the complexity of these systems. The goal of this investigation is to propose a modeling approach for the degradation of the battery performance during its aging, and to use such model to quantify the fuel economy and operability of a hybrid electric helicopter both in normal AirTaxi operation and in the case of engine failure. The proposed method is based on experimental data for lithium batteries retrieved in the literature. The battery model is included in a comprehensive simulation tool where the turboshaft engine and the electric machine are simulated with a simple but thorough approach that takes into account the part-load behavior of both energy converters. The present investigation also proposes and compares different strategies for the use of the battery during the AirTaxi mission showing that it is possible to reduce fuel consumption up to 11% when the battery is at the beginning of its life. When the battery comes close to its end of life, it is necessary to use an energy management strategy which ensures a sustainment of its state of charge at the expenses of a lower fuel saving.