Solar Reactor for Clean Fuel Production
In the framework of the EU-project Solarjet, scientists demonstrate for the first time the entire production path to liquid hydrocarbon fuels from water, CO2 and solar energy. The key component of the production process of sustainable “solar kerosene” is a high-temperature solar reactor developed by the group of Aldo Steinfeld, Professor of Renewable Energy Carriers at ETH Zurich and Head of the Solar Technology Laboratory at the Paul Scherrer Institute. The reactor contains a porous ceramic solar absorber made of the metal oxide ceria, which enables the molecular splitting of water and CO2 in a cyclic two-step reduction-oxidation (redox) process.
The first, energy-intensive step proceeds at 1500°C using concentrated solar radiation as the energy source. The metal oxide releases oxygen, assuming a reduced state. In the second step at 700°C, the reduced metal oxide reacts with water and CO2, thus re-acquiring oxygen. As the metal oxide is thereby returned to its original state, it can enter the next cycle of the redox process. The net chemical product is synthesis gas – or syngas – a gas mixture of hydrogen (H2) and carbon monoxide (CO), which serves as the precursor for the synthesis of liquid hydrocarbon fuels.
“We were able to successfully perform 240 consecutive cycles,” said Daniel Marxer, PhD student of Steinfeld’s group in a press release. The yield was 750 liters of syngas, which were shipped in a pressurized vessel from Zurich to Amsterdam. There, at a Shell research center, the solar syngas was finally converted into kerosene. It might also be possible in the future to obtain the required feedstock of CO2 from flue gas separation or directly from atmospheric air, thereby closing the material cycle for a CO2-neutral process.
The researchers from ETH Zurich conducted the EU funded project Solarjet together with the German Aerospace Center (DLR), the fuel company Shell, the think-tank Bauhaus Luftfahrt, and the consulting firm Arttic.