What do you need to make renewable liquid transportation fuels? Just sunlight, water and CO2, say researchers working on the partly EU-funded SUN-to-LIQUID project. The 4-year project was launched in 2016 with the aim of advancing breakthrough solar thermochemical technology developed in a previous EU-funded initiative. The alternative fuel technology in question has the potential to provide an unlimited supply of renewable transportation fuel from water, CO2 and concentrated sunlight. This is promising news for the transport industry, which is one of the largest consumers of fossil fuels and is currently faced with the challenge of reducing its carbon footprint. More specifically, it may have particularly important implications for long-haul aviation and shipping that are heavily reliant on hydrocarbon fuels.
Testing under real-world conditions
The SUN-to-LIQUID technology has been scaled up and tested at a solar fuel production plant constructed at project partner IMDEA Energy Institute located in Móstoles, Spain. The plant consists of a field of heliostats (movable mirrors used to reflect sunlight in a fixed direction), a solar reactor positioned at the top of a small tower and a gas-to-liquid conversion subsystem. “A sun-tracking field of heliostats concentrates sunlight by a factor of 2,500 – three times higher than current solar tower plants used for electricity generation,” explained Dr Manuel Romero of IMDEA Energy in a news item posted on the site of project coordinator Bauhaus Luftfahrt earlier this year. The intense flow of sunlight from these heliostats causes reaction temperatures of over 1 500 °C inside the solar reactor. The reactor then converts water and CO2 into synthesis gas, a mixture of hydrogen and carbon monoxide. This is then converted into kerosene, or jet fuel, in the on-site gas-to-liquid plant.
This technology may play a significant role in meeting global climate goals. Where the aviation industry is concerned, it can help to reduce net CO2 emissions by more than 90 % compared with jet fuel derived from fossils. Furthermore, it has the potential to cover the global fuel demand – which amounts to hundreds of millions of tonnes per year – in a way that is truly sustainable. The advantages don’t end there. Given that it doesn’t need cultivable land, the novel technology doesn’t compete with food or feed production. In fact, it could cover the global future fuel demand by taking up only a small fraction of the world’s desert area. Project partners predict that if solar fuel plants such as this were to be constructed on a large scale, the decarbonisation of the aviation sector could become a reality. Studies are currently being conducted on the industrial implementation of the SUN-to-LIQUID (SUNlight-to-LIQUID: Integrated solar-thermochemical synthesis of liquid hydrocarbon fuels) technology. Reporting in the same news item, Dr Andreas Sizmann of Bauhaus Luftfahrt stated: “[W]e are now a step closer to living on a renewable ‘energy income’ instead of burning our fossil ‘energy heritage’. This is a necessary step to protect our environment.” For more information, please see: SUN-to-LIQUID project website