Manned Aircraft Projects

Battery Technologies for Low-Emission Aviation

Electric flight is regarded as a key component of future climate-friendly mobility concepts. At the same time, aviation places particularly high demands on battery systems: in addition to achieving the highest possible energy density, battery cells must also meet high power requirements during take-off and landing, whilst operating safely and reliably over the long term.

However, the current state of the art still shows significant limitations. Conventional lithium-ion batteries lose a noticeable amount of energy density after repeated charge and discharge cycles and are reaching their limits, particularly in aviation applications. At the same time, development processes are often time-consuming, and digital simulation methods have so far been integrated only to a limited extent into material and cell development.

An Innovative Approach Involving Pre-Lithiation and Digital Development Support

The batterFLY project combines several innovative approaches to address these challenges. The focus is on developing battery cells with high-silicon, pre-lithiated anodes and nickel-based cathodes. Electrochemical pre-lithiation is intended to significantly improve both the energy density and the lifespan of the silicon anodes.

At the same time, novel electrolyte systems and simulation-based development processes are being employed. Digital models and simulations are incorporated into material, cell and system development right from the early stages. This is intended to shorten development times and ensure that the battery cells are specifically designed to meet the requirements of electric aircraft and subsequent certification processes.

“Aviation places completely different demands on batteries than traditional automotive applications. With batterFLY, we aim to combine materials, cell concepts and digital development approaches in such a way that high-performance yet safe batteries for future electric aircraft become a reality,” explains Prof. Dr Egbert Figgemeier, project coordinator at Helmholtz Institute Münster.

Interdisciplinary Collaboration Across the Entire Development Chain

In addition to Forschungszentrum Jülich, the project involves RWTH Aachen University, the Technical University of Munich, the Fraunhofer Institute for Solar Energy Systems ISE and the University of Stuttgart.

The project partners contribute complementary expertise in the fields of battery materials, electrochemistry, simulation, safety research and aeronautical engineering. This creates a close integration of basic research, cell development, safety assessment and aircraft integration.

An advisory industry and application board comprising representatives from the aviation and battery industries is supporting the project and assessing the industrial viability of the technologies developed. Participants include AIR ENERGY Entwicklungs GmbH & CoKG, Customcells Itzehoe GmbH, Lange Aviation GmbH, Pipistrel d.o.o. and Kristl, Seibt & Co. Gesellschaft m.b.H.

Contribution of the IFB

The Institute of Aircraft Design is developing the requirements for future battery systems for (hybrid) electric powertrains. Reference aircraft suitable for the targeted energy and power densities are selected on the basis of market studies. Battery-related TLARs are derived from these, which serve as relevant sizing parameters for the partners.

Preliminary work carried out by the IFB, as well as the certification specifications themselves, highlight highly configuration-specific requirements for (hybrid) electric powertrains. To this end, extensive operational, certification and safety investigations are being carried out to facilitate the certification process. This includes research into the protection against, or mitigation of, battery thermal runaway; a comparison of different battery usage and operating strategies; and the development of a toolchain for the automated assessment of the impact of faults and their effects on the electrical system, and their consequences for the relevant aircraft parameters. In this process, the relevant metrics for mapping the impact of faults at aircraft level, as well as the fault patterns specific to each component, are developed, defined and taken into account as part of the evaluation.

Finally, these findings will be used to evaluate the battery defined as part of the batterFLY project at the aircraft level. To this end, the battery cell will be examined in terms of its expected usability and regulatory compliance for the reference aircraft identified.

Project partners

• Forschungszentrum Jülich (Consortium leader)
• RWTH Aachen University
• Technical University of Munich
• Fraunhofer Institute for Solar Energy Systems ISE

Funding

Federal Ministry for Economic Affairs and Energy (German aviation research program LuFo VII-1)

Duration

January 2026 – December 2029

Contact

Andreas Bender, M.Sc.
Alexander Kieß, M.Sc.

Project description

CONCERTO is an EU-funded project, under the Clean Aviation Joint Undertaking programme. The project’s overall objective is to develop technical data which will constitute draft regulatory material for future breakthrough innovations.

Clean Aviation’s ambition to go over decisive impactful steps in demonstrated disruptive aircraft performance compatible with 2035 EIS will only be possible if the future regulatory framework is not an impediment to innovation. Certification shall still improve safety while shortening time to bring new safe products to market and into service, and maintaining European leadership and competitiveness. Having de-risked the certification path is therefore an important step. The project will deliver a comprehensive set of regulatory materials on certification together with preliminary description of methods of compliance applicable to the three "thrusts" of Clean Aviation and a first status of comprehensive digital framework of formalized collaborative tooled and model/simulation-based processes for certification.

The composition of the project consortium reflects a smart mix of aircraft manufacturers (CS-25, CS-23), engine manufacturers (CS-E), equipment manufacturers, research centers, universities, SME and PLM experts.

Contribution of the IFB

Within CONCERTO three major technology enablers are investigated. The focus lies on the usage of H2, an active wing and an electrified distribution and propulsion architecture (in short high voltage distribution – or HvD).

The institute of aircraft design is active within the HvD Proof of Concept (POC). Together with the consortium and the EASA, we aid in defining and organizing the PoCs for new principles and certification processes including the expected results and metrics and to define the targeted safety objectives and the operational environment (CONOPS) to develop applicable regulations and boundaries for the project. The Institute of Aircraft Design leads the certification and gap analysis processes, where results regarding the defined architecture are assessed given the current regulatory body (CS-23, SC-E19, CS-25, CS-E), where gaps shall be identified.

Further activities within CONCERTO will develop suggestions on how to fill these identified gaps, including the investigation of the use of simulation as means of compliance (MOC) for certification.

Project partners

For a full list of project partners see CORDIS Project page.

Funding

European Commission (Horizon Europe, JU Clean Aviation), Grant Agreement ID: 101101999

Duration

January 2023 – December 2026

Contact

Alexander Albrecht, M.Sc.

Acknowledgement

The project CONCERTO (GA ID: 101101999) is supported by the Clean Aviation Joint Undertaking and its members.

Project description

The EU-funded HyPoTraDe project will design, assemble, and ground-test a 500 kW modular fuel cell-battery hybrid electric DEP powertrain architectures, which includes a cryo-enabled thermal management for aeronautical powertrain applications. The ground-testing campaign will provide fast-track characterisation of the optimal system architecture, validation of failure mode mitigations for the ground-breaking powertrain, demonstration of complex operating requirements, and evaluation of the fail-safe capabilities of the modular powertrain. Further, the system will be complemented with a digital twin, validated using the results from the ground test campaign.

Contribution of IFB

The IFB is mainly involved in architectural trade-off studies. These will investigate different combinations of the main powertrain components, taking into account possible failure scenarios. The aim is to find an optimal powertrain architecture for a future hydrogen electric 19-seater aircraft. Furthermore, the institute supports the creation and validation of the digital twin.

Projektpartner

For a full list of project partners see CORDIS Project page

Finanzierung

European Commission (Horizon Europe, JU Clean Aviation), Grant Agreement ID: 101101998

Laufzeit

January 2023 – June 2026

Kontakt

Andreas Bender, M.Sc.

Acknowledgement

The project HyPoTraDe (GA ID: 101101998) is supported by the Clean Aviation Joint Undertaking and its members.

Aim of the project

Design, development and functional verification of a novel, structure-integrated skin heat exchanger concept based on a fiber composite foldcore sandwich structure

Project description

Aircraft with modern electrified propulsion systems, especially fuel cells, generate a large amount of unusable heat ("low quality heat", i.e. with a low temperature difference), which results in significantly increased cooling requirements. When using conventional cooling systems, this leads to proportionally larger cooling drag, which has so far severely limited the usability of such powertrains.

The aim of this project is therefore to develop a structurally integrated skin heat exchanger. This will consist of a fiber composite sandwich structure with a folded core. Due to their production using a continuous folding process, these form an open core structure that can be used to transport coolant over the entire size of the element. Structural integrity is ensured by the mechanical properties of the sandwich structure.

The project will investigate various aspects of this novel concept in order to provide a basis for future research. Important work items are:

• Investigation of the flow through the folded core structure for optimum coolant flow and heat transfer to the surface layers
• Modification of the fibers and the matrix to achieve high thermal conductivity of the surface layers
• Numerical investigation of heat transfer, adaptation/new development of existing methods and verification through laboratory tests
• Integration of the skin heat exchanger into the overall aircraft design and consideration of scalability
• Construction of a prototype for flight tests with the university's own research aircraft e-Genius to prove functionality. For ease of certification only on a non-load-bearing component will be used in the project, which means that the true potential cannot be fully utilized.

Project partners

• Institute of Aerospace Thermodynamics (ITLR), University of Stuttgart
• Institute of Aircraft Design (IFB), University of Stuttgart

Funding

Federal Ministry for Economic Affairs and Climate Action (German aviation research program LuFo VI-3)

Duration

October 2023 – September 2026

Contact

Alexander Albrecht, M.Sc.
Andreas Bender, M.Sc.
Dominik Eisenhut, M.Sc.
Jakob Gugliuzza, M.Sc.
Simon Thissen, M.Sc.

Project description

The aim of the SiFlA project is to reduce noise pollution and increase safety in general aviation by combining a quiet battery-electric drive with automated flight path guidance. This will be demonstrated using glider towing as an example. Flight path planning will take external influences such as wind and air traffic into account. The approach includes the design of a standardised, modular, high-capacity replaceable battery system, along with charging technology. For flight guidance, 3D flight path planning is being researched, which evaluates sensor data taking into account the flight mission and environmental conditions and converts it into control commands to the actuators for automated flight. A human-machine interface will display the flight path and safety-related traffic data to the crew. The sub-functions and the overall concept will be evaluated through flight tests and measurements, e.g. noise measurements.

Contribution of IFB

The IFB's main contribution is to provide the test aircraft for the innovative battery system and automated flight path planning, as well as to assist in developing the requirements for the battery system. In order to meet the high performance requirements for aerotow, the e-Genius will be equipped with a new, more powerful propulsion system and an autopilot. The final flight tests and noise measurements will also be carried out mainly by the IFB.

Projektpartner

• Institute for Flight Mechanics and Controls, University of Stuttgart
• Air Energy Entwicklungsgesellschaft mbH & Co. KG
• Garrecht Avionik GmbH

Finanzierung

Federal Ministry for Economic Affairs and Energy (German aviation research program LuFo VI-1)

Laufzeit

June 2021 – November 2024

Kontakt

Stefan Zistler, M.Sc.
Andreas Bender, M.Sc.

Content of the project

The scope of the project is to evaluate possible hybridisation concepts for the airship Zeppelin NT N07, that shall replace the current propulsion system. Especially the use of electric propulsors is being investigated. Different powertrain architectures are set up and compared with regard to criteria such as operating cost, fuel consumption and certifiability. The best suited option is identified and further developed into a complete system, that can be installed and certified in the airship in a future project.

Contribution of the IFB

The IFB has the main responsibility for the hybrid-electric powertrain. That includes researching suitable technologies with a high TRL and high availability, as well as compiling the regulations, guidelines and standards to be fulfilled for the components. Furthermore, the architectures and energy storages in question are defined and created by the IFB. The dimensioning of the powertrains to the performance data of the reference airship is also a task of the IFB, as is the acquisition of all relevant cost data for the components of the hybrid powertrains.

Project partners

ZLT Zeppelin Luftschifftechnik GmbH & Co. KG

Financing

Federal Ministry for Economic Affairs and Energy (German aviation research program LuFo VI-1)

Duration

October 2020 – March 2023

Contacts

Dipl.-Ing. Jonas Lay
Andreas Bender, M.Sc.

Content of the project

The scope of the project is the development of an optimized hybrid propulsion system for the aerial platform SK202 developed by Stemme RS, which may be operated as an optionally piloted vehicle (OPV).
The first propulsion chain should be based on a diesel-electric serial hybrid and the second should feature a hydrogen fuel cell as primary energy storage.

Reorganization:
As a consequence of the withdrawal of a partner, the specific aircraft could no longer be used and the project was reorganized to widen the use of the developing powertrain for all multiengine aircraft in the 2t range. This is why the architecture of the design was built generic and modular to allow the simple integration of an efficient, powerful and low-emission drive system into the various existing and future aircraft to-be. The newly defined output of the project is a power train demonstrator, that will be used for testing and later adaption and integration into a manned serial CS-23 aircraft.

Contribution of the IFB

Before the reorganization, the institute was responsible for the flight performance analysis, the layout and sizing of the hybrid system and the corresponding system architecture in terms of power distribution and means of control. Furthermore, the integration aspects and implications for all subsystems like the propulsors and batteries were investigated.

After the reorganization, the IFB focused on the control scheme and the interactions of the different subsystems. A key aspect of the multi engine setup calls for a dedicated safety and redundancy management. Besides the software development, the required components for the demonstrator were assessed, acquired and integrated. A flightworthy battery based on Li-Ion cells was developed and built twice. Furthermore, the initial operation and bench tests of the iron bird are conducted by the IFB in cooperation with all partners.

Project partners

• Reiner Stemme Utility Air Systems GmbH
• Steinbeis Flugzeug- und Leichtbau GmbH
• APUS Aeronautical Engineering GmbH
• Siemens eAircraft / Rolls-Royce Electrical (ass. Partner)
• Continental Aerospace Technologies GmbH (ass. Partner)

Financing

Federal Ministry for Economic Affairs and Energy (German aviation research program LuFo V-2)

Duration

January 2016 - October 2021

Contacts

Dipl.-Ing. Jonas Lay
Andreas Bender, M.Sc.