Thermochemical heat storage is still at a low TRL-level compared to sensible and latent heat storage. To improve its technological maturity simultaneous investigation on more than one length scale, ranging from molecular level up to system level, is required. In this work, the results of a multi-scale approach are presented to investigate the potential for thermochemical heat storage. On molecular scale, atomic-scale Density Functional Theory (DFT) calculations are performed, which are upscaled to molecular level via a Reactive Force Field (ReaxFF) approach. The newly developed ReaxFF approach is used for in-silico characterization of the material properties of magnesium and calcium chloride hydrates. On grain scale, the focus is on numerical and experimental analyses of the dehydration reaction kinetics and the accompanying heat and mass transfer processes. Lithium sulfate monohydrate (Li2SO4 ·H2O) is used as model material. Microscope experiments are carried out on the dehydration reaction of encapsulated single crystals of lithium sulfate monohydrate to gain insight into the nucleation process at the surface and the reaction kinetics in the substrate. On material scale, the challenge lies in synthesizing an optimized material showing enough thermal and mechanical stability, sufficiently fast kinetics and mass and heat transfer properties to obtain the required power, and adequately high enough energy density. Calcium chloride salt hydrate has been tested in its pure form, when encapsulated in an inert material and when impregnated in a porous matrix. On reactor scale, a detailed understanding of the transport phenomena for heat and mass transfer is needed. During the (de)hydration process in a cylindrical packed bed reactor, the wall creates radial effects due to heat losses, flow channeling and a non-uniform state of charge. A detailed 2D model for the transport phenomena in a packed bed is developed. The model is validated using experimental data measured in a 1L lab-scale setup and unique experimental results on adsorbed water concentration from MRI experiments. On system scale, an 8L lab-scale thermochemical heat storage system is constructed and optimized for providing hot tap water. Then, a proof-of-principle prototype is successfully built in order to demonstrate the feasibility of thermochemical heat storage for application in the built environment. The prototype consists of four reactor segments of 62.5L each.
|Titel||16th International Heat Transfer Conference, IHTC 2018|
|Status||Gepubliceerd - 1 aug 2018|
|Evenement||16th International Heat Transfer Conference, IHTC 2018 - Beijing, China|
Duur: 10 aug 2018 → 15 aug 2018
|Congres||16th International Heat Transfer Conference, IHTC 2018|
|Periode||10/08/18 → 15/08/18|