The development stages of technologies for renewable fuel production with high-impact and large-scale potential are challenging. The support of Future Cleantech Architects has enabled us to reach a massive worldwide audience with our R&D work on solar kerosene. This helps us presenting publicly funded projects to the general public.

Nathalie Monnerie & Stefan Brendelberger
Deutsches Zentrum für Luft- und Raumfahrt

In order to make your technology understandable, it is important to describe it well in few words. We have asked some of our key innovators for a short interview.

What is the key technology idea of Sun-to-Liquid and why do you believe in its future potential?

Nathalie: As part of the energy transition, the transport sector has an urgent need for alternative liquid fuels. The key idea of Sun-to-Liquid is the use of concentrated solar energy to produce green fuels, which can replace fossil fuels. The Sun-to-Liquid technology significantly reduces CO2 emissions compared to state-of-the-art technologies by using solar energy. The potential of these ideas and of the Sun-to-Liquid technology is huge.

Stefan: Sun-to-Liquid uses a thermochemical cycle to convert sunlight, water and CO2 into renewable kerosene. Some of the system’s components have been developed all new, others have been adapted to meet the requirements of the process. Especially the solar concentrator and the receiver-reactor with its reactive structures have made significant progress within the project.

The theoretical efficiency potential and the scale-up perspectives of this technology are very promising. Nevertheless, there are challenges to overcome to make this technology economically attractive - but many ideas and approaches are currently being discussed and explored within the community that could offer solutions.

How is your research consortium set up? Please describe the division of work in your cooperation.

Stefan: Sun-to-Liquid has a consortium of seven European partners. They cooperate within specific tasks with the following main responsibilities: Bauhaus Luftfahrt is the coordinator of Sun-to-Liquid and responsible for the techno-economic and environmental performance analysis. The demonstration plant is located on the premises of IMDEA Energia. They are responsible for the solar field construction and plant operation. ETH Zürich is leading the receiver-reactor development. HYGEAR is responsible for product treatment and gas to liquid conversion. The conceptual plant study and plant modelling at megawatt scale is led by DLR. Abengoa is responsible for the design of the solar field and tower in the scale-up study. ARTTIC is in charge of project management and communication.

Finally: what do you personally believe to be the most promising trends in cleantech development at the moment, besides solar kerosene?

Nathalie: I personally believe very much in the hydrogen economy, especially with green hydrogen of course, which can be produced with renewable energy, like solar or wind. Hydrogen can be used for transport applications as well as a base material for industrial processes. Hydrogen can also be used to store and transport renewable energy and use it to our liking: for the generation of electricity and heat, but also for the production of chemicals and future fuels.

Stefan: I personally also think that green hydrogen will play a major role in the decarbonization of many sectors – its challenges seem manageable and the chances coming with it are enormous.

When do you believe solar kerosene to become a viable, competitive option in air travel and transport?

Stefan: This will highly depend on political decisions on international level. Especially at the beginning solar kerosene will have higher costs than conventional kerosene. In order to boost the development of solar kerosene technologies this price gap has to be closed, for example by penalizing CO2 emissions or by setting minimum quota for renewable fuels in blends. The industry needs reliable boundary conditions to invest in adapting their processes and in implementing and developing such technologies.

Nathalie: Moreover, this is a question of costs and depends by a large part on eventual public financial incentives and penalties. For instance, if CO2 is taxed more heavily, green synthetic fuels could benefit. It will also depend on the willingness of the consumers to pay more for renewable alternative fuels.

The cooperation with FCA took place alongside the general support for the work of the German Aerospace Center and the specific support to the CNN series The Global Energy Challerge. What kind of support would you need to massively scale the technology until 2025?

Nathalie: Of course we will need more investment, also from private investors, and generally more interest from companies. Incentives from the states seem necessary to reach these goals.

Stefan: To me, the most important prerequisite for a successful market launch would be the introduction of minimum quota for solar kerosene. This could initiate a fair competition amongst suitable technologies. With quota and CO2 emission costs in place, a massive scale up could follow.