Nearly 80% of domestic energy is consumed in form of heat [1]. Therefore, thermochemical heat storage based on water vapour sorption by salt hydrates has become an interesting energy storage alternative.

During charging and discharging, water molecules move out and into the crystal structure. On macro scale, this movement leads to a recursive shrinkage and swelling of particles. For practical application, salt hydrates are often compacted to millimetre sized particles and loaded into a reactor-type vessel forming a packed bed. The volumetric changes of individual particles can be quite damaging to the performance of the bed, but they are difficult to visualise inside the reactor. Commonly, they are monitored with various optical techniques, which often give only the top view of the particle or particle bed. Nevertheless, to see what is happening on the inside, a destructive method has to be employed [3].

In this work we are looking at two non-destructive techniques that enable us to view reaction progress and morphological changes inside the reactor without the need for its disassembly. In neutron imaging we employ the contrast provided by proton density in anhydrous and hydrated sample to deduce the water content. With this technique we can follow the reaction process and the corresponding morphological changes almost in real time. What’s more, we can monitor water transport not only through the entire bed but through individual particles as well. In computer tomography we utilise the material density differences measured with x-rays to monitor the structural changes in the sample occurring during (de)hydration. With this work, we’re presenting and comparing novel research on visualising water transport in thermochemical particles and packed beds. Both techniques enable us to better understand and visualise the processes which were previously described only theoretically with the aid of equations. Moreover, they give us insights both into fundamental processes and engineering aspects of reactor design.

[1] https://ec.europa.eu/eurostat/statistics-explained/index.php/Energy_consumption_in_households Accessed on 22.01.2024

[2] Houben, Jelle. "Accelerating Thermochemical Energy Storage by Doping." (2023).

[3] M.Awais, et.al. "Kinetic Investigation of K2CO3 Composite at Reactor-Scale to analyze its Charging & Discharging Performance."