**4.1 Numerical and experimental study of ceramic-based CPCMs**

The optimized preparation process and suitable PCM make the ceramic-based inorganic salt CPCMs have excellent thermal properties, which solves the low thermal conductivity and leakage existing in traditional PCMs. However, a single heat storage unit cannot visualize the heat transfer process at the level of latent heat Thermal energy system (LTES), so system-level research has become one of the hotspots of research at this stage. Our group built a medium-high temperature packed-bed heat storage experimental platform in the laboratory to carry out system-level research [5, 58]. Through system-level simulation calculations and experiments, the thermal properties of the CPCMs within the TES are analyzed, which in turn could provide sufficient guidance for their wide-ranging applications.

Yao et al. [59] investigated the latent heat storage device of a 3D porous skeleton encapsulated PCM based on MCRT and FVM methods to systematically evaluate the heat transfer process under different design parameters. The results showed that the solar thermal efficiency and thermal storage efficiency increased by 71% and 94%, respectively. Li et al. [60] investigated a high-temperature packed-bed LTES with ceramic-based CPCMs and analyzed the heat transfer-flow behavior at the system level. The results show that the system exhibits higher charging/discharging efficiency. The heat transfer efficiency is enhanced when the radiative heat transfer influence is taken into consideration. Finally, the charging/discharging cycle decreases with the increase of the thermal conductivity enhancer.

In addition, Li et al. [61] investigated the thermal performance of MgO-based CPCMs from component to device levels, as shown in **Figure 9**. They analyze the crossscale problem of CPCMs from the unit-component-device level through numerical calculations and experiments. The CPCMs have MgO as the porous skeleton, NaLiCO3 as the PCM, and graphite as the thermal conductivity enhancer. The results show that the increase in the mass loading of the TCEM in the CPCMs module, and the entrance velocity of the HTF all improve the heat transfer performance at the component level. Zhao et al. [62] investigated the heat transfer process of two types of CPCM components for shell-and-tube TES: single-tube and concentric-tube components. Through

#### **Figure 9.**

*Schematic diagrams of a CPCMs module [61] (Reprinted with permission from Elsevier [OR APPLICABLE SOCIETY COPYRIGHT OWNER]).*
