Solar-powered tower for carbon neutral jet fuel production

Researchers have developed a carbon-neutral solar-powered aviation fuel production system that uses water, CO₂ and sunlight

This solar-powered fuel production system has been implemented in the field and the design could help the aviation industry become carbon neutral.

Currently, the aviation sector is responsible for about 5% of global anthropogenic emissions causing climate change, as it heavily relies on jet fuel called kerosene, which is a liquid hydrocarbon fuel typically derived from crude oil.

There are no clean alternatives available to power long-haul commercial flights on a global scale.

Researchers have therefore developed a system that uses solar energy to produce drop-in fuels, which are synthetic alternatives to fossil-derived fuels such as kerosene and diesel.

This project is a part of the European Union’s SUN-to-LIQUID project

Previous attempts to produce aviation fuels through the use of solar energy have mostly been performed in the laboratory. Steinfeld, a lead researcher, said: “We are the first to demonstrate the entire thermochemical process chain from water and CO₂ to kerosene in a fully-integrated solar tower system.

“With our solar technology, we have shown that we can produce synthetic kerosene from water and CO₂ instead of deriving it from fossil fuels. The amount of CO₂ emitted during kerosene combustion in a jet engine equals that consumed during its production in the solar plant.

“That makes the fuel carbon neutral, especially if we use CO₂ captured directly from the air as an ingredient, hopefully in the not-too-distant future.”

“A technological milestone towards the production of sustainable aviation fuels”

In 2017, the team started scaling up the design and built a solar fuel-production plant at IMDEA Energy Institute in Spain. The plant consists of 169 sun-tracking reflective panels that redirect and concentrate solar radiation into a solar reactor mounted on top of a tower.

The solar-made kerosene is fully compatible with the existing aviation infrastructure for fuel storage, distribution, and end use in jet engines. It can also be blended with fossil-derived kerosene.

The concentrated solar energy then drives oxidation-reduction (redox) reaction cycles in the solar reactor, which contains a porous structure made of ceria. The ceria –which is not consumed but can be used over and over – converts water and CO₂ injected into the reactor into syngas, a tailored mixture of hydrogen and carbon monoxide.

By improving the design, researchers could increase the efficiency to values over 15%

The syngas is sent into a gas-to-liquid converter, where it is finally processed into liquid hydrocarbon fuels that include kerosene and diesel – and from a nine-day run of the plant, the solar reactor’s energy efficiency (which is the portion of solar energy input that is converted into the energy content of the syngas produced) was around 4%.

“This solar tower fuel plant was operated with a setup relevant to industrial implementation, setting a technological milestone towards the production of sustainable aviation fuels,” Steinfeld says.

By improving the design, researchers could increase the efficiency of values by over 15%.