Prompted by the need for carbon-neutral fuels, which are imperative for the sustainability of aviation and maritime transport, and would certainly have many other uses, a group of researchers from ETH Zurich has developed a unique technology capable of producing liquid hydrocarbon fuels by utilising nothing more than sunlight and air.
The new recently demonstrated solar mini-refinery – located on the roof of ETH’s Machine Laboratory in Zurich – can make synthetic fuels that release no more CO2 during combustion than was harvested from the air for their production, hence the tag ‘carbon-neutral’.
During the demonstration, which took place under actual field conditions, the research team unveiled the entire thermochemical process, whereby the plant was able to extract CO2 and water from the air, split them into syngas – a mixture of gases that can be processed into kerosene, methanol or other hydrocarbons.
“This plant proves that carbon-neutral hydrocarbon fuels can be made from sunlight and air under real field conditions,” said ldo Steinfeld, Professor of Renewable Energy Carriers at ETH Zurich. “The thermochemical process utilises the entire solar spectrum and proceeds at high temperatures, enabling fast reactions and high efficiency.”
Once the CO2 and water collected from the air enter the solar reactor located at the focus of a parabolic reflector, which concentrates solar radiation by a factor of 3,000, and heat up to around 1,500 degrees Celsius, they are then split into syngas by way of the redox cycle, enabled by a cerium oxide-based ceramic structure at the heart of the reactor.
Developed as part of the EU SUN-to-LIQUID project, the mini-refinery – now capable of producing approximately one decilitre of fuel per day – will soon be ready for large-scale testing in a solar tower located near Madrid.
As a next step, the research team behind the project will continue working on making the mini-refinery competitive on the marked and suitable for industrial deployment.
“A solar plant spanning an area of one square kilometre could produce 20,000 litres of kerosene a day,” said Philipp Furler, Director (CTO) of Synhelion. “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.”