# Preparation and Characterization of CPCM for Thermal Energy Storage Unit
## 4 Conclusions  
By introducing a TESU, the performance of an ASHP heating system will be obviously improved. In order to identify a CPCM that can meet the TESU requirements, 10 CPCMs are prepared by the vacuum adsorption method, with the phase material LA absorbed in EG, and characterized. Conclusions can be drawn as follows.  
* The preparation of a CPCM is a physical process, and no chemical reaction happens. LA is effectively encapsulated in EG due to its capillary and surface tension, and the thermal stability of the CPCM is satisfied.
* Compared to LA, the phase change temperature of the CPCM changes little. Although the latent heat of the CPCM decreases due to the EG introduced, its thermal conductivity, supercooling degree, and volume expansion rate are significantly improved.
* Of the 10 CPCMs, the thermal performance of CPCM3 is better and more suitable for the TESU combined with an ASHP heating system.  
Figure 10: CPCM densities.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Name**} & \multirow{2}{*}{**CPCM Source**} & \multirow{2}{*}{\begin{tabular}{c} **Base** \\ **Material** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Latent Heat** \\ **(kJ/kg)** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Thermal** \\ **Conductivity** \\ **(W/(m-K))** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Phase** \\ **Transition** \\ **Temperature** \\ **(\({}^{\circ}\)C)** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Density** \\ **(kg/m\({}^{3}\))** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Degree of** \\ **Supercooling** \\ **(\({}^{\circ}\)C)** \\ \end{tabular} } \\ \hline \multirow{2}{*}{\begin{tabular}{c} CPCM3 \\ PCM-A-42 \\ PCM-M-40 \\ \end{tabular} } & \multirow{2}{*}{\
\begin{tabular}{c} This paper \\ Dongguan \\ Donglin \\ \end{tabular} } & LA+EG & 164.34–168.28 & 8.15–8.33 & 40.98–41.94 & 417–420 & 0.96 \\  & \multirow{2}{*}{
\begin{tabular}{c} PA \\ PMBA \\ \end{tabular} } & \multirow{2}{*}{198–200} & \multirow{2}{*}{0.2–0.25} & \multirow{2}{*}{42–43.5} & \multirow{2}{*}{780–850} & \multirow{2}{*}{1.5} \\  & & & & & & \\ \hline \hline \end{tabular}
\end{table}
Table 3: Performance comparison between CPCM3 and CPCMs commercially available.  
**Author Contributions:** Conceptualization, W.Z. ([PERSON]); Method, H.C.; Software, H.C.; Verification, W.Z. ([PERSON]) and Y.Z.; Formal Analysis, W.S.; Survey, Y.Z.; Resources, W.Z. ([PERSON]); Data Management, H.C.; Writing--Manuscript preparation, H.C.; Writing--Review and editing, W.Z. ([PERSON]); Visualization, H.C.; Supervisor W.Z. ([PERSON]); Project Management, H.C. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This research was supported by the National Natural Science Foundation of China with grant number 51466007.  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** No new data was created for this study or was not available due to privacy or ethical restrictions.  
**Conflicts of Interest:** The authors declare no conflict of interest.