Sorption-based long-term thermal energy storage

Research on a liquid sorption storage process is carried out with the working pair sodium hydroxide (NaOH)/water. This activity has started in 2002 with a first laboratory testing plant funded by the Swiss Federal Office of Energy (SFOE), followed by a pilot storage plant in an EU-funded FP7 project COMTES in 2013-2016. Recently, a novel heat and mass exchanger has been developed and tested. Optimization on power density is ongoing along with research on understanding the basic phenomenon of absorption from a gaseous into a liquid phase. In the frame of the Swiss Competence Center of Energy research “Heat and Electricity Storage” (SCCER HaE) and an SFOE Pilot and Demonstration project this research is followed by an upscaling process of the heat and mass exchanger along with its integration in the NEST research and innovation platform and ehub demonstrator. As part of participation in the combined IEA SHC Task 58 / ECES Annex 33 material characterization and evaluation along different scales, from materials to systems, is further carried out.

Figure 1: Pilot-scale storage plant combining long-term sorption storage and short-term sensible de-signed to cover yearly energy demand of a low-energy single family home (outside view left, inside view right).

Figure 2: a) Spiral finned tube heat and mass exchanger, b) Equilibrium curve based on mass fraction plotted against temperature differences encountered between absorber and evaporator (blue trian-gles) and between desorber and condenser (blue dots) taken from


Selected publications

Fumey, B.;  Weber, R.; Baldini, L., Sorption based long-term thermal energy storage – Process classification and analysis of performance limitations: A review. Renewable and Sustainable Energy Reviews 2019, 111, 57-74.

Fumey, B., Weber, R., & Baldini, L. (2017). Liquid sorption heat storage – a proof of concept based on lab measurements with a novel spiral fined heat and mass exchanger design. Applied Energy, 200, 215-225.

Weber, R., & Dorer, V. (2008). Long-term heat storage with NaOH. Vacuum, 82(7), 708-716.