Lakhasly

Thermochemical heat storage using silica gel offers high energy density, long storage, and minimal heat loss. While its performance is well-studied, the water binding within the gel and the storage mechanism require clarification. Using NMR, we analyzed water binding changes in silica gel before and after adsorption, defining the thermochemical reaction equation. Temperature and humidity's impact on adsorption was also examined. A theoretical heat storage density of 1029.63 kJ/kg was calculated, and kinetic analysis yielded an activation energy of 66.75 kJ/mol, suggesting a 3D diffusion model where water vapor diffusion in micropores is rate-limiting. Silica gel's heat storage density, ease of reaction, and cycling performance make it highly competitive.

The benefits of thermochemical heat storage include high-energy storage density, long storage time, and
negligible heat loss during storage. Silica gel has recently been widely studied as a heat storage material.
However, most of the research has focused on its heat storage performance in the reactor; the form of water
inside silica gel and the specific heat storage mechanism remain to be clarified. We employed nuclear magnetic
resonance to investigate changes in the internal water binding form and content of silica gel before and after
water adsorption and determined the equation for the thermochemical reaction. We further investigated the
effects of temperature and humidity on the adsorbability of silica gel. The theoretical heat-storage density of
silica gel was 1029.63 kJ/kg. Kinetic analyses of desorption gave an activation energy of 66.75 kJ/mol, sug
gesting that the most probable mechanism function is a 3D diffusion model. The diffusion of water vapor in
micropores is the limiting step for the reaction. Silica gel is highly competitive with other thermochemical heat-
storage materials, considering the heat-storage density, reaction difficulty, and cycling performance.