Seasonal thermal energy storage with aqueous sodium hydroxide - reaction zone development, manufacturing and first experimental assessments

In this paper, the theoretical and experimental investigation of the reaction zone construction of an absorption/desorption concept with sodium hydroxide (NaOH) and water is described. Both heat and mass exchangers – absorber/desorber (A/D) and evaporator/condenser (E/C) - constituting this reaction zone are falling film tube bundles working under reduced pressure (evacuated container). The different choices made for the construction of the reaction zone are outlined: the container as well as the manifold design, the vapour pathway with thermal radiation protection, the liquid level measurement cell and the tube bundle are described. After construction of the reaction zone, the work was focused on the first assessment of the A/D and E/C units in order to check their proper functioning. In this context, Helium leakage tests were carried out for the different components and an optical setup enabling to check the efficiency of the manifold with a substituted fluid is realized for the A/D unit.