Design considerations on energy storage system for electric aircraft propulsion

The growth of electric aircraft propulsion systems requires an accurate design of the battery energy storage system (BESS) and of the electric motor involved in the propulsion unit. The motor performance can be strictly linked to the characteristic of the BESS and to the variation of its parameters, as the output voltage. In this paper some design considerations are discussed with reference to the on-board BESS and to the choice of parameters of permanent magnet synchronous motors used in full electric aircraft propulsion. In particular, the problem is approached considering a speed and power profile of a realistic mission of a commercial small power twin engine four-seat aircraft. Some numerical investigations are carried out with the aim to compare performance achievable by the electric propulsion system in correspondence of different sizes and configurations of the batteries.

I. Introduction

The recent developments of the concept of All Electric Aircraft are increasing the interest in the design of proper and convenient electric propulsion systems for low-medium power aircraft [1]. The conventional propulsion systems, as thermal engine and gas turbine, represent the most part of current propulsion systems for aircraft. The application of electric motors to the aircraft propulsion is not a recent idea;however it is now becoming realistic due to the improvement of energy storage systems (ESS), like batteries, and/or of static electric generators as fuel cells (FC); moreover the electric propulsion can be introduced thanks to the availability of permanent magnet motors with very high power-density values. The main goals of the introduction of the electric propulsion are the reduction of pollution in the atmosphere, the possibility to increase the energetic efficiency of future aircraft, the possibility to reduce the frontal area of the motors in order to improve the aerodynamic behavior of the aircraft and the reduction of emitted noise with the increase of the passengers comfort. Some studies [2], [3] and some applications of hybrid electric aircraft are widely carried out by both academic researchers and companies in the world, in particular with the target of reducing fuel consumptionand increasing reliability and disposability of aircraft. On the contrary, the all electric propulsion is conceived in order to fulfill all the requirements for the proper functionality of the aircraft. The electric propulsion systems requirethe development of a strategy of on-board energy management and of optimization criteriafor electrical drives [4] and ESS [5] in order to reduce the weights and balance the loads onboard the aircraft, ensuring high reliability of the propulsion systems.