Under the leadership of Prof. Aldo Steinfeld from ETH Zurich, the European joint project SUN-to-LIQUID has now for the first time succeeded in producing solar kerosene. In short, solar fuel has been produced from water and CO2 using concentrated sunlight. This groundbreaking invention is an essential step towards future mobility, as it brings us a huge leap closer to our goal of using sustainable energy instead of using up fossil fuels. Especially as this reduces CO2 emissions by more than 90 percent in comparison to fossil fuels.

From the laboratory to a custom-built solar facility

In order to get this far at all, the researchers in the preceding SOLAR-JET project first developed the required technology and produced solar kerosene under laboratory conditions. SUN-to-LIQUID took the process to the next stage of development. An international team of scientists tested it on a custom-built solar facility on the premises of the IMDEA Energy Institute in Móstoles, Spain.

Dr. Manuel Romero from the IMDEA Energy Institute explains the principle:

“A heliostat field trailing the sun concentrates sunlight by a factor of 2500, which is three times the concentration that solar facilities currently use for long-distance power generation.“

The high solar radiation intensity was confirmed by flux density measurements carried out by the German Aerospace Center (DLR). It is capable of temperatures of more than 1500 degrees Celsius inside a solar reactor.

Thermochemical redox reaction

This in turn allowed for a so-called synthesis gas to be produced from water and CO2 through a thermochemical redox reaction – i.e. the transfer of electrons to another substance – inside the reactor designed by project partner ETH Zurich. It’s a compound of hydrogen and carbon monoxide. A custom-built Fischer-Tropsch unit, developed by project partner HyGear, converts this synthesis gas into kerosene on site.

Prof. Aldo Steinfeld from ETH Zurich, who is in charge of the development of the solar thermochemical reactor, notes with some satisfaction:

“The SUN-to-LIQUID reactor technology and integrated chemical unit have been verified under typical industrial fuel production conditions.”

Relevance to the transport sector

In addition to everyday use, solar kerosene is of particular interest to the transport sector. Dr. Andreas Sizmann from Bauhaus Luftfahrt, an interdisciplinary foundation established in 2005 and consisting of aerospace companies and the Bavarian State Ministry of Economic Affairs, Infrastructure, Transport and Technology, added this::

  “The demonstration of this technology could have a major impact on the transport sector, especially for aviation and shipping which still continue to rely on liquid fuels for long distances.”

It should also be noted that solar fuel production is best suited to desert locations. This means that there will be no competition with agricultural land. In the long term, the facility will extract the raw material CO2 from the atmosphere. The future global demand for kerosene can be thus met by regenerative solar fuels which are compatible with the existing fuel infrastructure.

DLR expertise

DLR has many years of experience at their disposal when it comes to developing solar thermochemical processes and their components. Within the SUN-to-LIQUID project, DLR has been responsible for measuring solar fields and concentrated solar radiation, for developing concepts for optimized heat recovery and – as was the case with the preceding Solar-Jet project – for making computer simulations of the reactor and the entire facility. Scientists from the DLR Institute of Solar Research and Combustion Technology used virtual models to scale up solar production of kerosene from the laboratory to megawatt scale, and to optimize the design and operation of the facility. For Sun-to-Liquid, DLR solar researchers developed a flux density measuring system which makes it possible to measure the intensity of highly concentrated solar radiation directly in front of the reactor, with a minimum of disruption to its operation. This data is indispensable for the safe operation of the facility and in order to determine the efficiency of the reactor.

About the project:

SUN-to-LIQUID is a four-year project funded by Horizon 2020 – the European Commission’s research and innovation funding program – and the Swiss State Secretariat for Education, Research and Innovation (SER). The project started in January 2016 and will end in December 2019. SUN-to-LIQUID brings together leading European research institutions and companies in the field of thermochemical solar research: ETH Zurich, IMDEA Energy, DLR, Abengoa Energía and HyGear Technology & Services Ltd. The coordinator Bauhaus Luftfahrt e.V. is responsible for the technology and systems analysis. ARTTIC supports the research consortium by providing project management and communication.

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