Reactor could produce fuel from sunlight

Aldo Steinfeld, a professor of mechanical and process engineering at ETH Zurich and head of the solar technology laboratory at PSI, led the team that developed the reactor with researchers at the California Institute of Technology in Pasadena, California.

The reactor makes use of a solar-driven thermochemical cycle for splitting CO₂ and H₂O using metal oxide redox reactions. The two-step cycle consists in thermally reducing non-stoichiometric cerium oxide at above 1,500°C and re-oxidising it with H₂O and CO₂ at below 900°C to produce H2 and CO — known as syngas, the precursor of liquid hydrocarbon fuels.

’The operation at high temperatures and the use of the entire solar spectrum provides a thermodynamically attractive path to solar fuel production,’ said Steinfeld.

The solar reactor consists of a cavity with a small windowed aperture into which concentrated solar radiation enters. The dimensions of the cavity ensure multiple internal reflections and efficient capture of the incoming solar energy. A porous, monolithic ceria cylinder inside the cavity is subjected to multiple heating and cooling cycles to induce fuel production. Reacting gases flow radially across the porous ceria cylinder, while products from the reaction exit the cavity through an axial outlet port.