The effect of crystal size on the thermal energy storage capacity of thickened Glauber's salt

Monodisperse Na2SO4·10H2O@SiO2 Microparticles against Supercooling and Phase Separation during Phase Change for Efficient Energy Storage

“…Meanwhile, the T c,p values are 17.62, 21.99, 25.89, and 26.23 °C, respectively, for microparticles with Na 2 SO 4 contents of 10.00% (w/v), 11.43% (w/v), 12.86% (w/v), and 17.14% (w/v) (Figure b). Thus, the values of T s for these SiO 2 microparticles are in the range from 8.65 to 14.83 °C, which are much lower than the T s values reported in the literature. , Such lower T s values are resulted from the effects of nucleating agent and crystal habit modifier in the inner fluid, and the good distribution of Na 2 SO 4 ·10H 2 O inside the confined nanospaces of the SiO 2 matrix. The results indicate the successful reduction of the supercooling to achieve energy storage and release at mild temperatures.…”

“…The effects of reaction time and Na 2 SO 4 content in the inner fluid on the microparticle morphology are systematically investigated. As shown in Figure , with fixed Na 2 SO 4 content, the microparticle morphology becomes smoother with increasing reaction time, because condensation with a longer time can lead to a denser SiO 2 matrix, which restricts further growth of the Na 2 SO 4 ·10H 2 O crystals . For microparticles fabricated with Na 2 SO 4 contents of 10% (w/v), 11.43% (w/v), and 12.86% (w/v), spherical shapes and smooth surfaces can be achieved when their reaction times reach 35, 45, and 55 h, respectively.…”

“…Due to the problems of supercooling and phase separation, it is difficult to achieve repeated energy storage/release at mild temperatures, which limits the practical applications. Although nucleating agents, crystal habit modifiers, and thickening agents are usually used to reduce the supercooling and phase separation of Na 2 SO 4 ·10H 2 O in industrial-scale crystallization, , there have not been any reports using such agents in Na 2 SO 4 ·10H 2 O encapsulated systems. Moreover, although porous particles encapsulated with Na 2 SO 4 ·10H 2 O show reduced supercooling and phase separation, , their high degree of supercooling (∼50 °C) limits their further use.…”

“…Meanwhile, Na 2 SO 4 in the droplets crystallizes into Na 2 SO 4 ·10H 2 O during the reaction process, leading to encapsulation of Na 2 SO 4 ·10H 2 O in the SiO 2 matrix of the resultant microparticles (Figure b5,b6). For such microparticles, supercooling is reduced by adding sodium borate (nucleating agents) and sodium hexametaphosphate (crystal habit modifiers) in the inner fluid, , to achieve a crystallization temperature at room temperature. Meanwhile, the encapsulated Na 2 SO 4 ·10H 2 O shows no phase separation due to the confined distribution in the mesoporous SiO 2 matrix, which also benefits the reduction of supercooling.…”

“…As shown in Figure 3, with fixed Na 2 SO 4 content, the microparticle morphology becomes smoother with increasing reaction time, because condensation with a longer time can lead to a denser SiO 2 matrix, which restricts further growth of the Na 2 SO 4 •10H 2 O crystals. 37 For microparticles fabricated with Na 2 SO 4 contents of 10% (w/v), 11.43% (w/v), and 12.86% (w/v), spherical shapes and smooth surfaces can be achieved when their reaction times reach 35, 45, and 55 h, respectively. However, with fixed reaction time, increase of the Na 2 SO 4 content can result in microparticles with poor morphology.…”