Researchers from ETH Zurich have produced liquid hydrocarbon fuels exclusively from sunlight and air. The scientists have developed a solar plant to produce synthetic liquid fuels that release as much CO2 during their combustion as previously extracted from the air for their production.
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Under real field conditions
"This plant proves that carbon-neutral hydrocarbon fuels can be made from sunlight and air under real field conditions. The thermochemical process utilizes the entire solar spectrum and proceeds at high temperatures, enabling fast reactions and high efficiency," said Aldo Steinfeld, Professor of Renewable Energy Carriers at ETH Zurich, and head of the research group that developed the technology.
The event marks the first time worldwide that the team demonstrates the entire thermochemical process chain under real field conditions. The new solar mini-refinery is located on the roof of ETH's Machine Laboratory building in Zurich.
The refinery produces around one decilitre of fuel per day. Now, Steinfeld and his group are working on a large-scale test of their solar reactor in a solar tower near Madrid.
"A solar plant spanning an area of one square kilometer could produce 20,000 liters of kerosene a day," said Philipp Furler, Director (CTO) of Synhelion and a former doctoral student in Steinfeld's group.
"Theoretically, a plant the size of Switzerland -- or a third of the Californian Mojave Desert -- could cover the kerosene needs of the entire aviation industry. Our goal for the future is to efficiently produce sustainable fuels with our technology and thereby mitigate global CO2 emissions."
Three thermochemical conversion processes
The process chain of the new system consists of three thermochemical conversion processes: the extraction of CO2 and water from the air, the solar-thermochemical splitting of CO2 and their liquefaction into hydrocarbons.
"CO2 and water are extracted directly from ambient air via an adsorption/desorption process. Both are then fed into the solar reactor at the focus of a parabolic reflector. Solar radiation is concentrated by a factor of 3,000, generating process heat at a temperature of 1,500 degrees Celsius inside the solar reactor. At the heart of the solar reactor is a ceramic structure made of cerium oxide, which enables a two-step reaction -- the redox cycle -- to split water and CO2 into syngas. This mixture of hydrogen and carbon monoxide can then be processed into liquid hydrocarbon fuels through conventional methanol or Fischer-Tropsch synthesis," explained the press release.