Experimental study of a LiCl/Silica gel sorption thermal energy storage prototype
High gas and electricity prices and the desire of decarbonizing the energy sector requires more utilization of renewable sources, such as solar energy. Considering residential applications in Middle and Norther Europe, high space heating demands exist along with low solar irradiation during winter. Nevertheless, a high solar irradiation intensity is available during summer. Seasonal thermal energy storage (STES) can be a solution to solve such a time mismatch . Sorption thermal energy storage (TES) technology is gaining attention in the last years for its potential application as long-term (e.g., seasonal) TES due its low thermal losses during the idle period (very important in long-term storage) and its high potential energy storage density. In a sorption TES, heat is stored thanks to the breakup of physical bonds between the sorbent material and the adsorbed fluid. Thus, as long as both elements are kept separated, the thermal losses are zero. Moreover, sorption TES is very suitable for residential applications since the adsorbent materials can be charged at regeneration temperatures below 100 ºC (no need of concentrating solar thermal collectors) and can be discharged at adsorption temperatures which match with the end user temperature of space heating systems . Sorption technology has been already studied in the literature for different applications (e.g., chillers, heat pumps, TES), mainly focused on material [3,4] and on small-scale adsorbent reactors . Furthermore, different materials have been studied: pure solid sorbent materials, composite sorbent materials and sorbent materials that can exploit also chemical reactions. Nevertheless, despite its potential, they have some intrinsic limitations that do not allow to reach the theoretical energy density values under real operating conditions . Selective water sorbents (SWS) or salt inside porous matrix composites (SPMCs), such as LiCl-silica gel, present several advantages over traditional adsorbents as long as the salt is hold inside the pores . SWS have been already studied at material level by Frazzica et al.  for the application in seasonal TES in Central and Northern Europe TES. The investigations have been carried out under the H2020 European project “SWS-Heating”. In the present study, the very first adsorption TES prototype has been preliminary experimentally investigated at ITAE laboratories (Italy). The adsorption heat exchanger of the first prototype is filled in with 8.9 kg of an SWS material manufactured by impregnating mesoporous silica gel with 30wt.% of LiCl.
Journal or Serie
XII National and III International Conference on Engineering Thermodynamics. 29 de junio, 2022, Universidad Carlos III de Madrid, Madrid