Enhanced inorganic salts stability using bentonite clay for high-performance and low-cost thermochemical energy storage

Abstract

The energy storage density, cycling stability, thermal conductivity, cost, and corrosive behavior character of chloride-based hydrated salts are the worth challenges facing the application of these materials for thermal energy storage (TES). However, the impregnation of these salts into porous sorbent materials represents a key tool to deal with these issues. This paper aims to develop low-cost thermochemical composites (CTCMs) based on natural bentonite and hydrated salts for TES application. Natural bentonite blended with graphite (BNTC) was used as a support to stabilize three hydrated salts SrCl2·6H2O, CaCl2·6H2O, and LiCl.H2O. Synthesis and microstructural characterization of BNTC@CaCl2, BNTC@LiCl, and BNTC@SrCl2 were reported. Suitable operating conditions optimization during the hydration reaction of the CTCMs was studied using thermogravimetric analysis. A great storage density of 854.5, 704.2, and 778.6 kJ.kg−1 were measured for BNTC@CaCl2, BNTC@LiCl, and BNTC@SrCl2, respectively. Consecutive desorption/sorption cycles experiments were conducted and good cycling stability of the CTCMs was recorded which reflects the ability of the natural bentonite to solve the worrying issue of salts solution leakage. The compatibility of CTCMs in contact with copper heat exchanger metal was assessed and a new composite coating film based on polyvinylidene Fluoride reinforced with zinc oxide nanoparticles (PVDF@ZnO) was proposed. According to the gravimetric measurements of coated copper metal, an excellent enhancement of copper corrosion resistance up to 94% was achieved under the charging phase conditions of the CTCMs.