# Energy Saving Potential of PCMs in Buildings under Future Climate Conditions
## 4 Results
### Effects of PCM on Heating and Cooling Loads  
The simulation results for the annual cooling and heating loads with and without a PCM are shown in Tables 5-8. The simulation results show that integrating PCMs has significant potential to reduce those annual loads now, as well as in 2020, 2050, and 2080 in Seoul, Tokyo, and Hong Kong. Those regions could achieve reductions in energy consumption by using PCMs to significantly decrease HVAC usage. The percentage of energy savings was calculated using Formula (6). Changing climate conditions will increase the cooling load in the summer and decrease the heating load in the winter. Integrating PCMs into building envelopes could reduce the annual cooling energy demand for HVAC operation and energy used to produce cold air in the building (see percent energy savings, Tables 6 and 8). \[\%\text{ of energy saving}=\frac{\text{Energy consumption without PCM}-\text{Energy consumption with PCM}}{\text{Energy consumption without PCM}}\times 100 \tag{6}\]  
The annual loads for cooling and heating with BioPCM and RubITHERPCM decreased more than with DuPonEnergainPCM because the former PCMs melt at 29 \({}^{\circ}\)C and 25 \({}^{\circ}\)C, respectively. As shown in Tables 5 and 7, Hong Kong, followed by Tokyo and Seoul, achieved the highest percentage of heating energy savings with BioPCM and RubITHERMPCM, whereas Seoul, followed by Tokyo and Hong Kong, had the highest percentage of cooling energy savings at the present, as well as in 2020, 2050, and 2080 (Tables 6 and 8). The differences shown by the results are a reflection of the melting point of the PCMs, the PCM position, and the local climate in the study zones. The melting temperatures of the PCMs used are appropriate for reducing the cooling and heating loads and thus providing significant benefits in both the cooling and heating seasons. The simulation results also show that energy requirements for HVAC system operation and the production of warm and cold air were low in 2020, 2050, and 2080 as a result of incorporating PCMs into the building envelope, which reduced the effects of climate change on energy requirements. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Region** & **PCM** & **Present (kWh)** & **2020 (kWh)** & **2050 (kWh)** & **2080 (kWh)** \\ \hline \multirow{3}{*}{Seoul, Korea} & Without PCM & 135,066 & 170,994 & 192,804 & 232,195 \\ \cline{2-6}  & BioPCM & 129,697 (3.98\%) & 165,445 (3.25\%) & 187,496 (2.75\%) & 227,720 (1.93\%) \\  & DuPonEneragain PCM & 132,025 (2.25\%) & 168,119 (1.68\%) & 189,986 (1.46\%) & 229,591 (1.12\%) \\  & RUBITHERMPCM & 130,188 (3.61\%) & 165,851 (3.01\%) & 187,928 (2.53\%) & 228,015 (1.80\%) \\ \hline \multirow{3}{*}{Tokyo, Japan} & Without PCM & 157,365 & 219,280 & 250,501 & 302,461 \\ \cline{2-6}  & BioPCM & 150,701 (4.24\%) & 213,733 (2.53\%) & 245,170 (2.13\%) & 298,020 (1.47\%) \\ \cline{2-6}  & DuPonEneragain PCM & 153,566 (2.41\%) & 216,324 (1.35\%) & 247,546 (1.18\%) & 299,543 (0.96\%) \\ \cline{2-6}  & RUBITHERMPCM & 151,416 (3.78\%) & 214,525 (2.17\%) & 246,139 (1.74\%) & 298,683 (1.25\%) \\ \hline \multirow{3}{*}{Hong Kong, China} & Without PCM & 339,322 & 380,804 & 412,229 & 459,115 \\ \cline{2-6}  & BioPCM & 335,230 (1.21\%) & 378,331 (0.65\%) & 269,064 & 462,885 \\ \cline{2-6}  & DuPonEneragain PCM & 336,022 (0.97\%) & 377,577 (0.85\%) & 408,977 (0.79\%) & 456,707 (0.52\%) \\ \cline{2-6}  & RUBITHERMPCM & 334,295 (1.48\%) & 376,257 (1.19\%) & 408,546 (0.89\%) & 457,373 (0.38\%) \\ \hline \hline \end{tabular}  
* Percent energy saving with PCM.  
\end{table} 
Table 6: Annual HVAC system energy loads to produce cold air in the cooling period.