In the northern German city of Jülich, the Swiss company Synhelion used sunlight to produce synthesis gas – on an industrial scale for the first time. A demonstration plant for the production of solar fuel will follow in 2023.
A receiver from Synhelion is used in Jülich to produce synthesis gas – a prototype is shown here. The device captures the sun’s rays and converts them into heat, which is used for chemical reactions.
Fuels that are obtained with the help of sunlight are a hope for air traffic: Because the development of such solar fuels should help to make transport through the air more climate-friendly. Now the company Synhelion – a spin-off from ETH Zurich – is reporting that they have taken an important step along this path.
For the first time, the company announced on Wednesday evening, it had produced synthesis gas on an industrial scale, with the only source of energy being sunlight. The project was successful on a facility of the German Aerospace Center in Jülich.
“Now the way has been paved for the industrial production of CO2-neutral aircraft fuels, which we want to start with next year in Jülich,” says engineer Philipp Good, the technical director of Synhelion. A liquid fuel can be produced from synthesis gas, a mixture of the gases hydrogen and carbon monoxide, using standardized industrial processes. In addition to kerosene, this also includes petrol and diesel.
Mirrors focus sunlight onto a receiver
The system in Jülich essentially consists of three parts: the solar mirrors, a receiver and a reforming reactor. The Synhelion receiver picks up sunlight focused by the mirrors. The maximum power received is 250 kilowatts. The receiver converts the light into heat and is connected to a “reforming reactor” made by Wood, an engineering company. The chemical conversion reactions take place in this reactor.
The receiver for capturing the sunlight is installed on a tower of the facility in Jülich.
Basically, only water and carbon are required for the production of synthesis gas. Synhelion extracts the carbon from carbon dioxide and methane. Both come from a biogas plant. “Biogas is an ideal source,” says Good. In this way, the carbon cycle remains closed: the carbon in the air eventually returns to it.
In the six meter high reforming reactor, temperatures of more than 600 degrees Celsius prevail during the chemical reactions. Around 100 cubic meters of synthesis gas per hour can be produced from the starting materials.
The full process will be tested in 2023
What is now needed next is a demonstration plant for solar fuels. Synhelion is already working on such a system – also in Jülich. With the help of the Fischer-Tropsch synthesis, the synthesis gas is to be converted into liquid fuels. With this system, the aim is to demonstrate the industrial feasibility of the entire process.
According to a projection by Synhelion, a plant of this scale is capable of producing 150,000 liters of liquid fuel per year. The fuel will then be used in the production of kerosene in a nearby refinery. The airline Swiss is planned to be the first buyer of the solar-produced fuel.
The problem of contrails remains
Solar fuels are therefore considered to be climate-friendly because the carbon dioxide that is produced when they are burned has ideally been extracted from the air beforehand. If airplanes are operated with solar fuel, the combustion of the kerosene no longer contributes to the man-made greenhouse effect.
However, this type of air traffic will still have a certain effect on the climate: Because contrails also heat up the earth’s atmosphere – and they occur even if the fuel was obtained in a climate-friendly way. However, Good points out that the formation of contrails can also be reduced when synthetic kerosene is burned.
It is currently difficult to say how much solar kerosene will cost in the future once industrial production is within reach. The processes are still significantly more expensive than the production of conventional aviation fuels. Synhelion’s goal is to achieve production costs that are competitive with other sustainable fuel technologies, Good says. And in the long term you want to be competitive with the prices for fossil fuels.