US team creates solar reactor that produces jet fuel from the sun

Carbon-neutral aviation, a term that sounds like science fiction, might be around the corner.

For decades, soaring across the sky without leaving behind a trail of carbon emissions has been a shared dream of scientists, environmentalists, and industry leaders alike.

Now, that dream is closer to becoming a reality thanks to the trailblazing work of researchers at Caltech, who have developed a solar-powered system that could change the future of sustainable flight.

They’ve successfully built a small-scale photothermocatalytic reactor that runs entirely on solar power without depending on electricity or fossil fuels.

This reactor captures solar heat and uses it to drive chemical reactions necessary to create fuel, bringing the world closer to carbon-neutral aviation.

Multi-layer solar absorber for maximum efficiency

This reactor stands out because its sophisticated solar absorber is carefully engineered to retain as much heat as possible while reducing losses.

The device features a layered structure of silicon, germanium, and gold, all deposited onto a silver base.

Above this assembly sits a quartz window, allowing sunlight to enter, and a vacuum layer that helps insulate the system.

“We’re not competing with concentrated solar technology, where you can reach up to 2,700 suns,” explains Aisulu Aitbekova, co-author of the study and a Kavli Nanoscience Institute Postdoctoral Scholar Research Associate at Caltech.

“We’re looking for a complementary technology, which can be used in areas where concentrated solar is not feasible.”

The result is a reactor that can reach temperatures up to 249°C under direct sunlight and maintain around 130°C during normal operation.

These conditions are sufficient to drive ethylene oligomerization—a process that converts simple hydrocarbon molecules into longer chains, the essential components of jet fuel.

Clean jet fuel creation without exploiting fossil fuels

The Caltech team demonstrated that their solar-powered reactor could take ethylene, a two-carbon molecule, and turn it into alkenes with seven to 26 carbon atoms—the exact range in conventional jet fuel.

This is accomplished without relying on burning fossil fuels or using external electricity.

“This device demonstrates that the heat generated by abundant solar energy can be used to directly drive catalytic processes, which has normally been done using electricity or fossil fuels,” says Harry Atwater, director of LiSA and Howard Hughes Professor of Applied Physics and Materials Science at Caltech.

Path to fully renewable aviation

While the current process starts with ethylene derived from fossil fuels, the LiSA team has made progress on producing ethylene from carbon dioxide, water, and sunlight alone.

This means that both steps can be driven entirely by solar energy, making ethylene and transforming it into fuel.

“So, now we show two steps: First, we use CO2, water, and sunlight to make ethylene, and then we do ethylene oligomerization. And solar energy is the only energy input to the system,” Aitbekova adds.

This achievement paves the way for sustainable and carbon-neutral fuel production.

With aviation among the hardest sectors to decarbonize, this breakthrough brings hope for a cleaner sky.

The study is published in the journal Device.