## 3 Results and Discussion  
### Thermal Property of As-Received PCMs  
The DSC results provided the onset temperature (T\({}_{\rm o}\)), peak temperature (T\({}_{\rm P}\)) as the melting temperature (T\({}_{\rm m}\)), end temperature (T\({}_{\rm e}\)), and latent heat (\(\Delta\)H) of the PCMs. Figure 3 shows thermograms of single-phase as-received PCMs using the test thermo-profile in Figure 2, and the measured thermophysical properties are summarized in Table 3.  
During the endothermic process of liquid -phase specimen 1 and solid-phase specimen 2, hills with two peaks were observed: the first peak at the melting temperature and the second peak resulting from superheating. The observation of multiple peaks indicated the test material had a crystalline structure or was multiphase. Although specimens 1 and 2 were marked as liquid and solid phases, they would have dual phases in which the second phase was assumed to have only a small portion. Inferring by comparing the magnitude of the second peak, the proportion of the second phase in specimen 2 was smaller than that in specimen 1. The observation of multiple peaks coincides well with [PERSON] and [PERSON]'s results [41], where DSC thermograms with multiple peaks were found under endothermic reaction. Figure 3: Dynamic DSC curve of single-phase PCMs: specimens (**a**) 1, (**b**) 2, (**c**) 3, and (**d**) 4. The reason was that the PCM had multiphases because additives were partially unmelted during heating. On the other hand, specimens 3 and 4 showed a single peak under the endothermic process, which was evidence of a single phase. The reference phase change temperatures were 21, 23, 27, and 30 \({}^{\circ}\)C for specimens 1 to 4, respectively. However, as shown in Figure 3 and Table 3, the measured melting temperatures of the PCMs were 31.3, 31.1, 28.9, and 33.8 \({}^{\circ}\)C for specimens 1 to 4, respectively. Multiphase specimens 1 and 2 had melting temperatures of 7 to 10 \({}^{\circ}\)C higher than the reference melting temperatures, whereas single-phase specimens 3 and 4 showed relatively small differences between measured and reference melting temperatures. In the literature, the difference has been explained by phase segregation [42; 43; 44] and superheating due to slurry or multiple phases [45]. [PERSON] et al. [46] demonstrated that the degree of superheating reduced as the composition of the major phase increased. All single-phase PCMs showed extreme supercooling under the exothermic process. Specimens 1 and 3 showed two connected peaks, whereas specimen 2 showed one peak, and specimen 4 showed two separated peaks, which occurred as a small eutectic impurity peak during the exothermic process and as a main peak for the supercooling issue [47]. In [PERSON] and [PERSON]'s study on paraffin-based organic PCMs [48], the supercooling was only about \(-5\) \({}^{\circ}\)C. However, their measured solidification temperatures were lower by 30-40 \({}^{\circ}\)C than their measured melting temperatures (Table 3). In inorganic PCMs based on salt hydrates, supercooling is related to a slow rate of nucleation or nuclei growth [9; 45]. In addition, DSC has a cooling rate much higher than field applications. A sufficiently slow cooling rate should be selected considering supercooling. [PERSON] [12] demonstrated that a much slower cooling rate, rather than a typical cooling rate between 5 and 10 K/min, was suitable for low-thermal-conductivity PCMs to avoid supercooling. However, low cooling rates can reduce the signal-to-noise ratio, which reduces the accuracy of measurement. The latent heats of specimens 1 to 4 under the endothermic process were 157.3, 176.8, 146.0, and 161.0 J/g, respectively, at temperature ranges of 23 to 44 \({}^{\circ}\)C. The latent heats of fusion for specimens 1 to 4 under the exothermic process were 135.4, 152.5, 131.0, and 157.2 J/g, respectively.