ETH Zurich scientists have found a new way to produce jet and diesel fuel without harmful emissions.
Using this technique, engineers built a “solar tower” in Spain – a station that uses only carbon dioxide, water, and sunlight to generate fuel. Currently, the system converts only 4% of solar energy into jet fuel, but the authors claim that they can increase the system’s efficiency by up to 15%.
The Solar Tower was developed as part of the EU SUN-to-LIQUID project and built in collaboration with the Spanish water institute IMDEA. The idea of scientists was to organize waste-free, environmentally friendly, and energy-intensive synthetic fuel production using renewable energy sources.
The new solution is based on photovoltaic panels and a system for converting carbon – one of the primary sources of emissions on the planet – into functional diesel and kerosene.
According to New Atlas, the pilot plant is powered by a concentration of solar thermal energy. An array of 169 panels, each measuring three square meters, receives the sun’s rays and redirects them into a 16-centimeter hole in the tower’s reactor. This reactor, installed at the base of a 15-meter tower, receives on average about 50 kW of thermal energy per unit time.
The resulting heat is used to run a two-stage thermochemical redox cycle. Water, along with pure carbon dioxide, creates a reaction based on cerium, which simultaneously converts them into hydrogen and carbon monoxide or syngas.
Because all of the described processes take place in a single chamber, the control engineer can adjust the water and CO2 feed rates to determine the composition of the synthesis gas in real-time.
As a result, the station can generate aviation kerosene and diesel fuel. The scientists noted that the composition of the obtained substances does not differ from the materials used by airlines and automakers, which means that the technology can be scaled up and transferred to commercial industries. However, before that, the authors will have to optimize the efficiency of their solution.
According to the results of the study, the scientists ran the tower for nine days, performing six to eight thermochemical cycles a day, weather permitting. Each process lasted an average of 53 minutes, and the total duration of the experiment was 55 hours.
Several cycles had to be stopped due to overheating when the temperature in the reactor exceeded the specified 1450 °C and reached a critical level of 1500 °C. During this time, scientists collected about 5,191 liters of synthesis gas, which is approximately 4% efficient in using the collected solar energy.
According to project leader Aldo Steinfeld, the team is targeting commercial use cases and intends to increase the station’s efficiency to at least 15%.