Can aircraft also do without fossil fuels? Physicist Prof. Dr. Andreas Timmermann, member of the board of the Berlin Brandenburg Aerospace Alliance (BBAA), explains the current state of research.
DM: Prof. Dr Timmermann, at present there is apparently only the possibility of using low-emission fuel. Are zero emissions not yet technically possible?
Prof. Dr Timmermann: Yes, it is technically possible. But for safety reasons, the approval does not yet allow 100 % synthetic kerosine to be used. These synthetic fuels, which burn much more cleanly than normal kerosine, may only be mixed with up to 50 %. This is called blending. This means that fuels are added to the aircraft which then consist of 50 % normal paraffin and 50 % synthetic kerosine. We here in Berlin and Brandenburg are currently working very intensively in this area to improve the situation.
DM: That means the Berlin Brandenburg Aerospace Alliance (BBAA) network has its own research facility?
Prof. Dr Timmermann: We are working together with research institutions. We want to try to put the existing research results into practice and to develop this synthetic paraffin at airports in such sufficient quantities that we can reduce emissions in smaller aircraft. This means that the network of companies and research institutions interested in aerospace here in the Berlin- Brandenburg region is very practice-oriented and wants to contribute to the implementation in large-scale aviation, with project funding from the Federal Ministry of Economics, the Ministry of Economics of the State of Brandenburg and the EU.
DM: Within the framework of the network, however, you are initially only carrying out the transfer of knowledge on a smaller scale?
Prof. Dr Timmermann: It makes sense to try this out with smaller aircraft first, in order to learn from it how to implement these ideas with larger ones. But we are already doing this in our region with developments for larger aircraft. Here in Brandenburg we also have one of the largest engine manufacturers in the world; in Dahlewitz, south of Berlin, Rolls Royce Germany has begun to develop low-emission aircraft engines and electric motors.
DM: How is synthetic kerosine actually produced?
Prof. Dr Timmermann: Basically, it is an old process. Hydrocarbons are used together with energy, which nowadays is best obtained from green electricity, from wind or solar energy. Together with CO2, this can be combined via chemical processes to produce any fuel by first producing hydrogen and then using this hydrogen together with CO2 to produce petrol, for example, or synthetic kerosine. You can also use the hydrogen directly or convert it into electricity via a fuel cell. But you always have to be aware that hydrogen is a very explosive element, which of course also harbours dangers. It has to be carefully weighed up and must be safe throughout the entire process, from production to transport to storage within the aircraft.
DM: How can hydrogen be stored and transported? It would be obvious to produce it in regions that have a lot of sunshine, such as Australia or Africa, and then transport it here?
Prof. Dr Timmermann: Correct. This is currently being discussed in various countries, also with German politicians, for example to deliver hydrogen from North Africa to Europe via pipelines or to transport it via tankers. But you have to transport the hydrogen, unless you produce it directly on site, for example at smaller airports. We want to show that you can actually produce enough hydrogen or synthetic kerosine decentrally with smaller plants that it is actually sufficient for flight operations.
Two and a half years ago, Airbus presented a study according to which they operate aircraft in the short medium-haul range with hydrogen. I think it is very ambitious to achieve this for aviation in general by 2035. However, using hydrogen or even synthetic fuels to achieve emission reductions is indisputable.
DM: What other research is going on at the moment?
Prof. Dr Timmermann: For short-haul flights, I can imagine aircraft being powered by hydrogen in tanks, in the wings or even in the fuselage, for example, together with a fuel cell and propeller-driven electric motors. For medium- and longhaul flights, however, we will have to rely on synthetic fuels. We have to look for solutions to reduce emissions even in the existing fleets of large aircraft. And this is where synthetic paraffin can make an important contribution.
DM: And the conversion is technically not a problem?
Prof. Dr Timmermann: It is not so much a question of conversion. It is already possible to add 50 % synthetic kerosine to this fuel with small modifications to the engines and, as studies have shown, reduce emissions by more than 50 %. But we have the problem that this synthetic kerosine is not being produced anywhere near enough worldwide because it is still very expensive. Hydrogen is also expensive to produce.
Interview Marie Wildermann