Two-component water sorbent with mesoporous ordered matrix and CaCl2 was prepared by wet impregnation. The composite has ordered mesoporous structure with 2D-hexagonal pore arrangement and maintain its structure after the wet impregnation with CaCl2 solution. The ordered two-composite water adsorbent and the matrix reveal high water uptakes. The ordered two-component composite is rather low hydrophilic adsorbent. For significant improvement of the hydrophilic character higher amount of CaCl2 in the matrix is needed. At present the composite for the application within an adsorption heat storage is still too hydrophobic, since the major water uptake occurs only at relative pressure above 0.6. However, by wet impregnation, a successful shift of the isotherm to lower relative pressure was achieved. Since the overall volume was only slightly reduced by the impregnation, this is the first promising step which shows the principle possibility towards further optimization of this two-component water sorbent material.
COBISS.SI-ID: 4977690
We have developed a mechanism that predicts the heat storage potential of numerous known or new microporous aluminophosphates. The utilisation of the reversible chemical and physical sorption of water on solids provides a new long-term thermal energy storage concept, also in combination with solar thermal collectors. However, up to now there have been no systematic studies of the possible mechanisms for heat storage enhancement concerning materials optimisation. Based on a comparative thermogravimetric and calorimetric study of water sorption in small-pore aluminophosphate materials (SAPO-34, AlPO4-18 and APO-Tric) we proposed, that the formation of highly ordered water clusters in the pores is a driving force for a sudden water uptake in a narrow relative pressure range, which is a prerequisite for their use in storage systems and crucially determines their sorption efficiency. The formation of clusters is enabled by rapid and reversible changes in the framework aluminium coordination and optimal pore diameters.
COBISS.SI-ID: 4910618
A new two-component (composite) water sorbent CaCl2-FeKIL2 has been developed for sorption-based solar thermal energy storage. The matrix of the composite is FeKIL2 material with disordered mesopores, high surface area of 712 m2/g and mesopore dimensions between 4 and 29 nm. The composite, prepared by wet impregnation of FeKIL2 with CaCl2, has lower surface area (418 m2/g) and similar mesopore dimensions as the matrix. The maximum water sorption capacity of FeKIL2 is 0.21 g/g, while the composite possesses 3 times higher maximum water sorption capacity due to the presence of the salt in the matrix. Heat of adsorption of the composite is 50.4 kJ/mol. A short-term cycling test between temperatures of 150 and 40 °C at a water vapour pressure of 5.6 kPa confirms a comparatively good hydrothermal stability of the composite.
COBISS.SI-ID: 5034778