In the course of the energy transition, scientists are looking for ways to improve the efficiency of solar power generation and storage. The “High Performance Solar 2” (HPS2) research project, funded by the Federal Ministry for Economic Affairs and Energy, brings together an international team to develop the use of salt as a heat transfer medium in “parabolic trough” solar power plants.

Currently parabolic trough plants use thermal oil as a medium to transfer heat – the oil absorbs solar radiation collected by parabolic mirrors, converts it into heat and transfers it via pipelines to a heat storage unit or a steam turbine to generate electricity. But if molten salt was used instead of oil to transport and store heat, it could do so at significantly higher operating temperatures – up to 565 degrees Celsius (compared to 400 degrees Celsius for oil) and hold it for longer (up to twelve hours).

The German Aerospace Center (DLR) Institute of Solar Research is working together with the University of Évora (owner of the Évora Molten Salt Platform in Portugal) and companies from Germany and Spain, to set up a demonstration plant. The collector modules of the HelioTrough® 2.0 generator, supplied by TSK Flagsol GmbH, provide a total thermal output of up to 3.5 MW across a total length of 684 metres. The solar salt (a mixture of potassium nitrate and sodium nitrate) has been developed by Yara International ASA and could also be used for solar process heat supply systems. By the end of the project, the partners aim to increase operating temperatures to 500 degrees Celsius.

"Power plants using the technology from HPS2 can be built more easily and operate more efficiently. This reduces electricity production costs by up to ten percent," explains Mark Schmitz from TSK Flagsol in a press release by the German Aerospace Center (DLR). "That is an enormous step for a single technical change.”