Feasibility study for a medium-range regional aircraft retrofit with battery powered propulsion system

In this paper battery-electric retrofits for a medium-range regional aircraft, comparable to the ATR 42- 500, are analysed for five different technology scenarios. The methodology and component models are described in detail as well as the validation of both the methodology and the aircraft model against conventionally powered aircraft. Based on the assumptions used, the present study reveals that battery-electric retrofits are likely not possible in the near-term future. Only when heavily relaxing the mission requirements and significantly decreasing the range retrofits become possible. For a 2050 technology scenario the range of the battery-electric retrofit is only about 280 km

Load Flow Analysis of Hybrid AC-DC Power Systems for the Application in Electrified Aircraft Propulsion

To reduce the emissions of aviation the electrification of aircraft propulsion is of particular research inter- est. Here, the power provided to the electric propulsors is distributed within the powertrain either in form of direct or alternating current. Therefore, an implementation of power flow simulation is presented, which can be used in aircraft powertrain sizing. The methodology enables bidirectional power flow and adds the possibility to change the voltage level between buses within the system. Furthermore, the proposed methodology accounts for functional dependencies of system parameters, like the converter efficiency on the power flow. The methodology is validated and exemplary applied on an electrified propulsion system topology

H2Electra – a platform for comparative analysis of integration concepts for hydrogen-based electric propulsion in regional aircraft

Over the past decade numerous novel concepts for electric flight have been elaborated. Each unique in its own way and based on various assumptions and technological advances projected for the future. Within each concept design decisions have to be made on component level, propulsion system level and aircraft level. In order to be able to evaluate and analyse both, advanced components technologies and innovative propulsion system architectures, as well as to understand the effect of each design decision, a common baseline platform has been developed to allow for comparative analyses. This work presents such a platform with the hydrogen-based electrified regional aircraft concept called H2Electra. The iterative design process developed for this purpose is presented. It allows for a holistic approach to the development of an aircraft, its electrified propulsion system as well as the sizing of the components therein. Two propulsion system integration concepts are being considered in the evaluation: one partially fuselage-integrated and one nacelle-integrated. Challenges and trade-offs between the two concepts were analysed and evaluated, with safety and reliability being key design and decision-making metrics, alongside block-fuel efficiency and power density. In particular, the design decision on a suitable bus voltage and its effect on the powertrain sizing and integration were investigated

Analytical model for electric machine sizing in electrified aviation

Decreasing the green-house gas emissions of aviation industry may be achieved by an electrification of aircraft propulsion. The new electrified powertrain architectures need to be analysed regarding their potential, wherefore a modelling of electrified components has to be done. The present study introduces an analytical model for sizing an electric machine. The model sizes the volume, mass and efficiency of the machine taking geometrical parameters and thermal limitations into account

Potential of metal hydride-based range extenders for commuter aircraft

Using alternative fuels like hydrogen in electrified propulsion systems is one possible approach for reducing aircraft emissions. The development of safe hydrogen storage with acceptable energy densities is an essential challenge being addressed in current research. Metal hydrides enable inherently safe and long term hydrogen storage. While also offering high volumetric storage densities, they achieve only low gravimetric storage densities. These properties impede the use of metal hydrides as a primary hydrogen storage in aviation. Nevertheless, their application may still be favorable for secondary hydrogen storage devices. This paper analyses the applicability of hydrides for the range extension of a commuter aircraft to allow a diversion to an alternate airport. Therefore, various hydride types, such as complex hydrides, hydride slurry and metal hydrides combined with compressed hydrogen storage, are sized and benchmarked against competing energy carriers, such as compressed hydrogen, liquid hydrogen and batteries, to evaluate their potential and determine future research needs. Although the results of the evaluation show that hydride range extenders can be beneficial from the safety point of view, their application as a range extender for the diversion would entail a reduction of the flight mission's range or payload

H2Electra – a platform for comparative analysis of integration concepts for hydrogen-based electric propulsion in regional aircraft

Over the past decade numerous novel concepts for electric flight have been elaborated. Each unique in its own way and based on various assumptions and technological advances projected for the future. Within each concept design decisions have to be made on component level, propulsion system level and aircraft level. In order to be able to evaluate and analyse both, advanced components technologies and innovative propulsion system architectures, as well as to understand the effect of each design decision, a common baseline platform has been developed to allow for comparative analyses. This work presents such a platform with the hydrogen-based electrified regional aircraft concept called H2Electra. The iterative design process developed for this purpose is presented. It allows for a holistic approach to the development of an aircraft, its electrified propulsion system as well as the sizing of the components therein. Two propulsion system integration concepts are being considered in the evaluation: one partially fuselage-integrated and one nacelle-integrated. Challenges and trade-offs between the two concepts were analysed and evaluated, with safety and reliability being key design and decision-making metrics, alongside block-fuel efficiency and power density. In particular, the design decision on a suitable bus voltage and its effect on the powertrain sizing and integration were investigated

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

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