Modelling of a battery supported fuel cell electric power train topology for a regional aircraft

Abstract

Electrification of aircraft propulsion may offer a way towards carbon dioxide (CO2) neutral air travel. Here, the electric aircraft demonstrators already flying mostly rely on the use of batteries as energy source. While battery electric concepts may be suitable solutions for short range applications, such as urban air vehicles, the energy density of state of the art batteries is not yet sufficient to power regional aircraft with a typical range of 1000 nautical miles and 70 passengers. One possible topology option of a propulsion concept suitable for a regional aircraft is a hybrid composed of a fuel cell system (FCS) and a battery. On the one hand, this concept uses hydrogen (H2) as the primary energy carrier, resulting in a significant reduction of the required battery stack mass in comparison to a battery only aircraft. On the other hand, a battery support of flight phases with high power demand, such as take-off or climb, allows a smaller dimensioning of the fuel cell system and the corresponding thermal management system (TMS) and therefore additional overall system mass benefits in comparison to a fuel cell only aircraft. The present paper analyses the weight reduction potential of a battery stack supported fuel cell system electric power train architecture for a typical regional aircraft with regard to the hybridization factor (HF) and battery specific energy (BSE). The modelling includes the sizing of the fuel cell system and the battery stack, other mechanical and electric components, such as gearboxes, electric motors and power electronics and the corresponding TMS. The according electrified aircraft is resized, keeping wing loading and power-to-weight ratio constant. The best combination of HF and BSE yielding the lowest MTOM with 27 100 kg is still about 19.9 % heavier than the conventionally powered reference aircraft with 22 800 kg. The study shows that future aircraft of similar weight and hence size require very advanced battery technology with regard to the BSE compared to available state of the art solutions.