Composite based on lithium chloride and highly porous silica gel for adsorptive heat storage systems

Adsorption Heat Storage is an emerging technology that can address the time mismatch between energy supply and demand, thus offering effective use of low-temperature heat from renewable sources. In order to enhance the efficiency of heat storage systems, development of advanced adsorbents with large sorption capacity under operating conditions of a specific working cycle is required. Composite sorbents "Salt in a porous matrix" are promising materials in terms of sorption capacity and tuneability of sorption properties. This article presents a new composite based on LiCl inside a silica gel with a large pore volume (Vp ≥ 2 cm3/g), which allows embedding as high as 42 wt% LiCl. The composite demonstrates high sorption capacity of 0.53 gH2O/gads and high energy storage capacity 1.4 kJ/g under conditions of a daily adsorption heat storage cycle. The sorption dynamics was investigated by Large Pressure Jump and Large Temperature Jump methods. Heat transfer coefficients of 170 and 225 W/(m2K) are evaluated for adsorption and desorption stages, respectively. The values of the specific power of the heat release and storage in the considered cycle are calculated as 3.1 kW/kg and 5.8 kW/kg, respectively. These results show a high potential of the new composite for heat storage.