Enhancing the heat storage density of silica-alumina by addition of hygroscopic salts (CaCl2, Ba(OH)(2), and LiNO3)
Résumé
This work aims to develop new composite materials presenting a high energy density accompanied with an optimal sorption capacity for seasonal heat storage. Silica-alumina was selected as host material and various quantities of calcium chloride, barium hydroxide and lithium nitrate were deposited on it by incipient wetness impregnation. The obtained composites were fully characterized in their structural, textural, and surface properties, and the water sorption/desorption heats were determined by TG-DSC analysis for all composites, salts, and support. A detailed analysis of the dehydration steps is reported for the three salts. The heat released and the quantity of adsorbed water were found to depend on various parameters such as the amount of accessible salt, the dispersion of the salt on the surface and/or into the porous matrix, and the hydration level of the deposited salt hydrates. The TG-DSC results revealed that the heat released per gram of material increases with the amount of calcium chloride and lithium nitrate, while it remains nearly constant with the barium hydroxide loading. Due to its high heat of water sorption and low cost, the composite containing 15 wt% of calcium chloride (738 kJ kg(sample)(-1)) appears to be the most promising compared to lithium nitrate or barium hydroxide composites (609 and 408 kJ kg(sample)(-1) respectively). CaCl2/silica-alumina composites reveal to be potential candidates to thermochemically store energy. (C) 2015 Elsevier B.V. All rights reserved.