Synhelion, a Swiss cleantech company founded in 2016, develops a solar receiver-reactor that utilizes the concentrated solar energy and ceria redox material to convert COâ‚‚ and water into renewable syngas, which is then used to synthesize kerosene via the conventional Fischer-Tropsch (FT) synthesis process.
(This article contains 5 diagrams and 1987 words.)
Challenges: jet fuel
Due to its high specific gravimetric energy density, kerosene is widely used as a jet fuel for long-haul aviation. Kerosene jet fuel combustion produces carbon dioxide (COâ‚‚) emission. A round-trip flight from Frankfurt to New York, for example, burns about 156,500 kg of jet fuel. This results in about 570 tons of COâ‚‚ or an average of 870 kg COâ‚‚ per passenger. Global aviation is responsible for approximately 5% of the current anthropogenic emissions causing climate change, and this percentage is expected to rise.
Kerosene is produced by fractional distillation of crude oil in an oil refinery. Alternatively, kerosene can be synthesized from syngas—a specific mixture of hydrogen (H₂) and carbon monoxide (CO)—using the well-established Fischer-Tropsch synthesis process. However, the technological challenge is to generate renewable syngas from water (H₂O) and CO₂ using solar energy.
Synhelion Technology
Synhelion develops a solar receiver-reactor that uses concentrated solar energy in a solar tower configuration and reticulated porous ceria redox material to convert CO₂ and water into syngas with a desirable molar ratio of H₂ and CO. The syngas is then used to synthesize  kerosene via the established Fischer-Tropsch synthesis process.
How Synhelion turns CO2 to jet fuel
As schematically depicted in the figure below, the solar tower power fuel plant integrates three subsystems:
- the solar tower concentrating facility,
- the solar receiver-reactor, and
- the gas-to-liquid unit.
The solar tower concentrating facility is equipped with a solar tower and heliostat field. It deflects concentrated sunlight of 2,500 suns to 4,000 suns (1 sun = 1 kW/m²) onto a solar receiver-reactor. The solar receiver-reactor is mounted on top of the solar tower and aimed at the power-weighted center of the heliostat field. It converts CO₂ and H₂O into syngas with a desirable molar ratio of H₂ to CO for Fischer-Tropsch synthesis.
The products together with unreacted COâ‚‚ and Hâ‚‚O are delivered to a gas-to-liquid unit on the ground adjacent to the solar tower. The gas-to-liquid unit uses over 90% of syngas to produce kerosene. Unreacted COâ‚‚ and Hâ‚‚O are injected back to the solar receiver-reactor.
The most critical subsystem in the solar tower power fuel plant is the Synhelion’s innovative solar receiver-reactor. The diagram below schematically depicts the structure of the solar receiver-reactor.