Photo: DLR (CC-BY 3.0)

On the road to hydrogen aviation

In the BALIS project, the German Aerospace Center (DLR) is developing the world’s first fuel cell drivetrain for aircraft – with a megawatt capacity. DLR is thus taking another step towards enabling emission-free flying with hydrogen. On 21 January 2021, the Parliamentary State Secretary presented the funding decision for the BALIS project amounting to 26 million euros to the Federal Minister of Transport and Digital Infrastructure (BMVI) Steffen Bilger at a digital event at the DLR Institute of Technical Thermodynamics in Stuttgart.

“This decade is about turning the lever and switching our mobility to low-carbon fuels. Mobility with hydrogen from renewable energies plays an essential role in this. Hydrogen can be used as fuel in all modes of transport, including aircraft. The goal is zero-emission aviation – preferably with jobs and added value in Germany, said Parliamentary State Secretary Steffen Bilger at the handover of the funding decision.

“Whether in the air, by road and rail or at sea – DLR is one of the pioneers in the development and application of fuel cells and can draw on the know-how and experience gained from years of research. With projects such as BALIS, we will continue to set standards tomorrow: towards zero-emission mobility, which is based on hydrogen as another pillar in our energy system,” explained Prof. Karsten Lemmer, Member of the DLR Executive Board for Energy and Transport.

“The BALIS project shows that hydrogen propulsion in aviation is real and feasible. We are thus continuing the success story of the National Innovation Programme for Hydrogen and Fuel Cell Technology (NIP), with which the National Organisation for Hydrogen and Fuel Cell Technology (NOW) and the project promoter Jülich (PtJ) have been systematically developing hydrogen and fuel cell technologies from the research and development stage to market since 2008, using funding from the Federal Ministry of Transport. The NIP was and is a pillar of the national hydrogen strategy. Only with highly innovative technologies can Germany successfully participate in a global hydrogen economy,” says Kurt-Christoph von Knobelsdorff, Managing Director of NOW.

Focus: Fuel cell drivetrain and unique test environment

The aim of the BALIS project is to develop and test a fuel cell powertrain with an output of around 1.5 megawatts. This would allow a regional aircraft with 40 to 60 seats and a range of 1,000 kilometers to be realized. DLR is setting up a test stand unique in this form. It forms the necessary overall system, i.e. the complete hardware and the necessary infrastructure: these include the fuel cell system itself, the hydrogen tanks, the electric motor as well as the control and control technology. This test environment is complex and at the same time very flexible. It enables research and development work under a wide range of framework conditions, requirements and guidelines in the aviation sector.

“With BALIS, we are creating the energy conversion technology bases, developing a first demonstration system of the 1.5 megawatt performance class and developing an optimal mode of operation. In the next step, we want to put it into use together with partners from science and industry,” explains Prof. André Thess, Director of the DLR Institute of Technical Thermodynamics, adding: “The focus is initially on the use in aviation. However, such fuel cell systems can also be used in heavy goods vehicles, for example in large commercial vehicles on the road, on trains or in ships.”

Sound barrier 1.5 megawatts: New generation of fuel cell systems

Most fuel cells, which are already commercially available, have a modular output of 100 to 200 kilowatts. In order to reach the megawatt range, however, it is not possible to combine any number of smaller systems. This is where technology sets limits. “At 1.5 megawatts, there is a ‘sound limit’ in terms of the architecture and performance of today’s components of fuel cell systems,” says Prof. Josef Kallo, DLR expert on hydrogen in aviation. “We want to cross the border and at the same time bring together as few so-called high-performance fuel cell stacks as possible. To do this, we need new approaches and new components, for example in the area of optimized current density distribution, voltage level, handling of liquid hydrogen in large quantities and coupling to an overall drive system.”