Since the beginning of 2020, scientists at the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) have been working together on the designs of climate-neutral commercial aircraft in the EXACT project (Exploration of Electric Aircraft Concepts and Technologies). The concept of a fleet consisting of regional, short-haul and medium-haul aircraft with a wide range of propulsion concepts is now available as an interim result. These include regional aircraft with distributed electric drives and short- and medium-haul aircraft with turboprop and turbofan drives. These can be operated hybrid-electrically by means of hydrogen fuel cells as well as by direct combustion of hydrogen or sustainable aviation fuels (SAF).
"Especially between the technology options based on hydrogen and SAF, a race is emerging. We would now like to take the aircraft concepts and energy scenarios we have developed forward together with partners from industry and science and deepen them in joint cooperation projects for climate-neutral aviation," explains project leader Dr. Johannes Hartmann from the DLR Institute for System Architectures in Aviation in Hamburg.
Both the full life cycle of the aircraft and the process of extracting, transporting and delivering renewable fuels have now been comprehensively considered in the climate impact analysis of the new configurations. The overall goal of the EXACT project is to design new aircraft configurations that can be operational with at least 70 seats and a range of 2,000 kilometers by 2035. The innovative aircraft designs are to use new technologies to eliminate CO2 emissions. To this end, the project team first studied conventional propulsion systems in order to understand them in detail. From these findings, the team was able to develop different propulsion concepts and possible aircraft configurations, as well as evaluate their interaction in an entire fleet of different aircraft sizes.
Climate neutral from the start
The collaboration of 20 DLR institutes with their respective expertise and joint system competence makes it possible to consider and consider the entire life cycle of an aircraft - from production and operation to decommissioning and subsequent recycling. To this end, the project team has designed all the components of the respective aircraft in detail and examined how they interact.
"Next, we want to look at certification and industrialization requirements in more detail in joint projects with industry," says Hartmann "Medium-sized companies in particular can use our aircraft concepts to plan the pre-development of their supplier parts for larger industrial operations at an early stage."
In the near future, SAF could already reduce the climate impact. In the long term, these, like direct hydrogen combustion, offer the potential to reduce the climate impact by up to 90 percent. However, completely different technologies are needed for hydrogen-powered aircraft. In addition, airport infrastructures and maintenance operations will have to be adapted, and aviation personnel will have to be retrained.
There is also a special focus on looking at the life cycle - not only of the aircraft, but also of the individual energy sources. The engineers and scientists are investigating the environmental impact of individual aircraft types from design to decommissioning. By environmental impact, the researchers mean not only the emission of CO2 and greenhouse gases, but also, for example, water consumption or the contamination of soils by pollutants. This means they also look at the impact on the environment and climate before an aircraft component is produced and what happens to the materials after recycling.
"Green" energy sources
Green electricity and water are needed to produce enough "green" hydrogen. In special industrial processes, the hydrogen is further processed into SAF. The EXACT project is investigating scenarios for transporting the energy sources to the places where aviation takes place in the most sustainable way possible. "Directly linking such issues to aircraft design and technology development is completely new in our project. Petroleum has always been extracted from the earth and processed in refineries to produce kerosene. Producing sustainable fuels is much more complex. Solar power, for example, could be generated in the desert, and water is available on coasts. In EXACT, we are researching how these energy sources can be transported and processed as efficiently as possible so that they can ultimately be used in aircraft," says Hartmann. The scientists are already taking fuel production into account in scenarios for sustainable energy generation with subsequent production of hydrogen and SAF when planning new types of aircraft. They link this to the correspondingly necessary infrastructure so that a new aviation system is planned from the outset to be sustainable and economically operable.
In the second half of the project, holistic solutions are now to be found in which the technology modules interlock optimally. Only then will it be possible to make a final, reliable assessment of the various technologies and energy sources in terms of their impact on the climate.
via: DLR
