The advantages of fuel from renewable energies are enormous. For example, solar kerosene reduces CO2 emissions by more than 90% compared to fossil fuel, as the plant pulls the raw material CO2 from the atmosphere. In contrast to biofuel, there is no competition with food production during the process.
A process unique in the world
For the project, the seven partners have installed a unique solar plant in Móstoles, Spain. A heliostat field consisting of almost 170 focusing mirrors collects the sunlight and concentrates it 2,500 times. This produces temperatures of over 1,500 °C (2,732 °F), which are required for the subsequent process. The basic idea is to reverse the combustion process. The process uses carbon dioxide and water as raw materials, draws energy from sunlight and thus produces fuel.
In detail, the corresponding thermochemical process consists of two steps. First, oxygen is released in a specially developed reactor made from a metal oxide, which serves as a reactant, at around 1,500 °C (2,732 °F). The researchers then pass carbon dioxide and water vapor through the reactor at around 700 °C (1,292 °F). Both react with the oxygen-deficient metal oxide and release oxygen. The result is a synthesis gas – a mixture of hydrogen and carbon monoxide, each with a very high degree of purity.
The synthesis gas is then converted into kerosene using the Fischer–Tropsch process. The use of Fischer–Tropsch kerosene is already permitted today, allowing the solar fuel to be blended with conventional turbo-combustion engine fuels without any further approval procedures.
Solar kerosene is possible
The project partners in the predecessing SOLAR-JET project showed that the process works – but only under laboratory conditions. In June, for the very first time, solar kerosene was produced under real conditions in a pilot project.
The SUN-to-LIQUID project 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 B.V. The coordinator Bauhaus Luftfahrt e.V. is responsible for the technology and systems analysis. ARTTIC supports the research consortium in terms of project management and communication.
SUN-to-LIQUID is funded under Horizon 2020 and will be continued until December 2019. Until then, the plant will be subjected to a continuous load during production operation and will provide valuable insights for future reactor and plant developments during research operation. These will be incorporated into future projects in order to achieve the goal of commercial production of solar kerosene.