Energy Sector
Source: ETH Zurich
Imagine a metallic tower wrapped in the reflections of thousands of mirrors tracking the sun like technological sunflowers. At its peak, a gleaming cylinder gathers all that energy to capture carbon dioxide from the air and transform it into clean fuel. It’s real. And it’s happening.
It may sound like magic, but it’s pure science. Thanks to this cutting-edge technology, we can dream of a world where CO₂ becomes raw material to power planes, ships, and heavy machinery.
Developed by the Swiss Federal Institute of Technology in Zurich (ETH Zurich), this innovation shows that the sun’s energy can do more than just generate electricity —it can regenerate the air we breathe and drive sustainable mobility, even in sectors that today seem nearly impossible to decarbonise. But what exactly is a solar reactor?
What is a solar reactor, and how does it produce clean fuel?
A solar reactor is not a conventional solar plant or thermal facility. It’s a system that harnesses extreme, concentrated solar heat through a field of heliostats (sun-tracking mirrors) to trigger a controlled chemical reaction inside.
The process converts CO₂ and water vapour (H₂O) into a mixture of gases known as syngas, composed of hydrogen (H₂) and carbon monoxide (CO). This syngas is the base material used to produce sustainable liquid fuels, such as synthetic kerosene for aviation.
A design with both visual and climate impact
The Swiss prototype is only a few meters tall. However, its architecture is reminiscent of facilities like the Daguangshan solar plant in China, where advanced thermochemical technologies have also been tested.
Such reactors could be integrated into existing facilities or developed as part of large-scale solar parks, turning sun-drenched regions into hubs for clean liquid fuel production.
From CO₂ to kerosene: The step-by-step chemical process
1. Direct air capture
The system begins by absorbing air from the atmosphere using a direct CO2 capture unit. This technology is already being applied in other fields, such as in Iceland, where CO₂ is injected underground. Still, it serves here as the feedstock for the solar reactor.
2. Solar concentration and heat generation
Sunlight, redirected by thousands of heliostats, is focused into the reactor chamber. Inside, temperatures reach up to 1,500 °C, high enough to trigger thermochemical reactions.
3. Reaction with metal oxides
Within the reactor, a ceramic material —typically ceria (cerium oxide)— acts as a catalyst. When heated, the oxide releases oxygen. As it cools in the presence of CO2 and H2O, it reacts with them to produce syngas.
4. Liquid fuel synthesis
This syngas is processed through the Fischer-Tropsch synthesis, producing liquid hydrocarbons such as synthetic kerosene, synthetic diesel, or synthetic gasoline. Key point: These fuels are fully compatible with existing infrastructure. Their use emits only the CO2 that was previously captured, effectively closing the cycle.
Source: ETH Zurich
Why this breakthrough is a game-changer
It represents progress in sectors that are hard to electrify.
Aviation: Liquid fuels provide high energy density, enabling long-haul flights without compromising range or safety.
Maritime transport: Ships need high-capacity, easily storable fuels —and solar reactors can provide them.
Heavy industry (steel, cement): These sectors require extremely high temperatures. Solar-derived fuels can meet those demands sustainably, without sacrificing performance.
Instead of releasing pollutants into the atmosphere, these industries could rely on solar and carbon-neutral fuels while keeping their businesses intact without redesigning engines or infrastructure.
The key? This fuel isn’t extracted from the ground —it’s created from sunlight and air.
Advantages over other energy solutions
- Makes use of limited land surfaces without interfering with crops, ensuring compatibility with food security.
- Fits into existing infrastructure, since it produces liquid fuels already compatible with today’s transport and distribution systems.
- Captures CO2 already present in the atmosphere and reuses it in production, avoiding extra carbon emissions and supporting climate balance.
Scalable in regions with high solar radiation, such as southern Europe, North Africa, or the southwestern United States.
What challenges lie ahead? Scalability and industrial adoption
The main challenge is making the technology economically viable on a large scale.
The process is still more expensive than conventional fuels. However, costs are expected to drop thanks to more efficient, durable materials; automated solar concentration systems; and the integration with industrial-scale direct air capture networks.
The future: Solar-powered circular energy
Picture cities where car emissions feed their own transport systems. Airports where captured runway CO2 becomes the next flight’s fuel. Industries generating their own energy without an added carbon footprint.
And most inspiring of all: This is no longer science fiction. We’re already seeing functional prototypes delivering results. If the sun already provides us with light and electricity, why not also mobility and industrial heat?
