Scientists have created fuel from sunlight and thin air, opening the way to carbon-neutral hydrocarbon fuels.
Researchers called their discovery ‘an important milestone’ that could ultimately help decarbonise the aviation sector, but said a lot of work is still needed to upscale the process.
Transport and aviation contribute around 8% to total carbon dioxide emissions that are attributed to human activities.
Innovative: Scientists have created fuel using sunlight and thin air for the first time. This opens the door to the production of carbon-neutral hydrocarbons fuels. This is the solar fuel system.
The mini-refinery produces liquid fuel from sunlight and air. It works by three processes. The first is to capture water and carbon dioxide from air. These are then fed into a solar reactor which converts them to a mixture of hydrogen and carbon monoxide (syngas). This is then transformed into many other hydrocarbons like methanol.
The system starts by extracting water from the air (pictured above).
The mini-refinery system works by first extracting water and carbon dioxide from the air.
These are then fed into the solar reactor, which converts them to a mixture of hydrogen and carbon monoxide (syngas).
The syngas is then converted into liquid hydrocarbons. These can include gasoline, methanol, or other fuels to create an alternative power source.
Researchers state that while the individual steps of the solar energy production process have been demonstrated, it is difficult to put the whole system into practice in real-world conditions.
Aldo and colleagues from ETH Zurich, Switzerland, describe the solar fuel system on the roof top of a laboratory.
It consisted of three important units.
They include a direct-air capture unit that extracts carbon dioxide from ambient, the solar-redox unit that uses sunlight to convert carbon dioxide and/or water into a mixture carbon monoxide/hydrogen (syngas), as well as a gas-to liquid unit that converts methanol to liquid hydrocarbons.
Scientists found that the experimental system was stable and worked well under intermittent solar radiation.
They claimed that it produced 32 methanol per day in a seven-hour period, which is a demonstration of the technical viability for a solar fuel production process.
The water and carbon dioxide then go into a solar-powered reactor that converts them into a mixture carbon monoxide/hydrogen (pictured).
The syngas is then converted into liquid hydrocarbons. These can include gasoline, kerosene, or other fuels to create an alternative power source (pictured).
How it works: The system consists of a direct air capture unit, which extracts carbon dioxide from ambient air (bottomleft), a solar-redox unit that converts carbon dioxide and carbon monoxide into a mixture with hydrogen and carbon monoxide (main), and a gas to liquid unit that converts syngas into liquid hydrocarbons or to methanol (bottomright).
The authors also calculated a scheme to meet the global demand for aviation fuel consumption, which was 414 Billion litres in 2019.
They estimate that the production plants would require 45,000 km2, which is approximately 0.5% of the Sahara Desert’s area.
However, the first generation commercial solar plants would produce more fuels than the fossil kerosene that they are supposed to replace.
Researchers wrote in Nature: “Stable outdoor operation under intermittent sun radiation convincingly proves the technical viability” of the thermochemical chain that converts sunlight and ambient air into drop-in energy.
“But bringing such renewable fuels to market will require substantial process optimization and upscaling. This should be supported with policy schemes that allow market introduction at a commercial scale.
They conclude that the demonstration that carbon-neutral hydrocarbons can be produced using sunlight, air, and water is an important milestone that could lead to developments necessary for the long-term decarbonisation.