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A project to further develop solar-thermal-energy storage technology

| By Gerald Ondrey

Synhelion S.A. (Lugano, Switzerland; and the Swiss Federal Laboratories for Materials Science and Technology (Empa; Dübendorf; are conducting a joint research project, co-funded by the Swiss Innovation Agency Innosuisse, to further develop a high-temperature energy-storage technology that is a key component in the production of climate-friendly solar fuels. The project will enable the cost-effective and scalable storage of high-temperature solar heat at over 1,000°C for the first time. The storage technology is expected to be used in Synhelion’s first industrial-scale solar fuel production facility, which will be built in 2022.

Synhelion produces sustainable fuels, such as gasoline, diesel and kerosene that are compatible with conventional internal combustion engines and jet engines. The ETH Zurich spin-off has developed a solar thermochemical process based on process heat generated from concentrated sunlight to produce these synthetic fuels (see Solar Chemistry Heats Up, Chem. Eng., March 2018, pp. 12–16). To enable the chemical reactors for solar fuel production to operate around the clock, a cost-effective, high-temperature thermal energy storage (TES) is needed. This solution stores part of the solar energy to be used during the night and cloudy periods, enabling continuous operation of the reactors, thereby significantly increasing plant capacity and drastically reducing capital expenditure.

Currently, there is no TES on the market that is compatible with the high temperatures, cycle times and heat-transfer fluid of Synhelion’s technology. For this reason, Synhelion is further developing the solid heat-storage technology, enabling the storage of high-temperature solar heat of over 1,000°C in a cost-effective and scalable manner for the first time. As part of the research project with Empa, storage and insulation capabilities will be optimized in terms of material costs, high specific heat capacity and service life. Additionally, a design for Synhelion’s industrial-scale solar-fuel plant is being developed.