The Other Solar Power: How Scientists Are Making Fuel From Sunlight and Air

This story appeared in the July/Aug 2020 situation as “The Other Solar Electricity.” Subscribe to Discover magazine for far more stories like this.


Couple actions swell our carbon footprint quite like traveling. A a single-hour flight on a twin-motor jet aircraft burns nearly 6,000 pounds of kerosene and adds nearly 19,000 pounds of carbon dioxide to the environment. The environmental impression of air journey is so stark that Swedes even have a expression for it: flygskam, or flight disgrace. But what if traveling could be manufactured zero carbon?

“We have produced a solar know-how that is in a position to generate liquid fuels making use of just two ingredients: solar power and ambient air,” suggests Aldo Steinfeld, a renewable power pro at the Swiss Federal Institute of Know-how. “These hydrocarbon fuels release only as significantly carbon dioxide through combustion as was earlier extracted from the air.”

It may well appear to be like alchemy, but the solar refinery Steinfeld has helped build in Móstoles, on the outskirts of Madrid, follows some uncomplicated chemistry. An array of mirrors known as a heliostat tracks the sunshine, boosting the sunlight’s depth by a factor of 2,500 when reflecting it onto a 50-foot-large tower.

This dazzling beam of mild heats a reactor with a core manufactured of cerium oxide, an cheap compound typically applied to polish glass. At 2,seven hundred levels Fahrenheit, oxygen is liberated from the cerium and eradicated, after which h2o and carbon dioxide captured from the air are injected into the reactor. As the reactor cools, the lessened cerium claws again oxygen molecules from the additional material, leaving a combination of hydrogen and carbon monoxide known as syngas. This is funneled into a second reactor, exactly where the syngas is converted into kerosene molecules. In June 2019, the Móstoles refinery announced its initially trickle of gasoline.

But why turn solar power into gasoline at all? Even though highway and rail transport are open to electrification, existing battery know-how does not pack the punch desired to generate hefty industries these kinds of as sea freight and air journey. “There is no way all around jet gasoline for lengthy-haul industrial aviation,” suggests Steinfeld. “Can you imagine a Boeing or Airbus traveling trans-Atlantic on batteries? I assume it violates the legal guidelines of physics.”

Solar kerosene has the likely to slot into existing worldwide infrastructure for storing, transporting and making use of fossil fuels. But it nonetheless can not compete with them for value: It would possible ring up all around $9 for every gallon if it is offered to customers. But that price tag really should drop as the know-how enhances in efficiency and grows in scale. Steinfeld believes that, with a modest raise in latest efficiency, solar refineries could offer the complete world’s jet aviation gasoline demand with a heliostat array the size of Indiana.

This revolution is underway. Past May well, a important airport in the Netherlands announced it would host the world’s initially plant turning atmospheric carbon dioxide into liquid gasoline. Climeworks — a enterprise spun out from Steinfeld’s lab in 2009 — is giving the modules that will capture carbon dioxide from the air.

And what of our flygskam? “If the jet gasoline is created from sunlight and air, then there is almost nothing to be ashamed of since the carbon footprint would be zero,” suggests Steinfeld. “A real sustainable process.”


Frank Swain is a science author centered in Barcelona, Spain.