# Storage Capacity in Dependency of Supercooling and Cycle Stability of Different PCM Emulsions
## 3 Results and Discussion
### PCM Emulsions
#### 3.1.2 Storage Capacities
One reason for this is the higher share of enthalpy within the second phase transition at a lower temperature for the P16-97 emulsion, which has 12.2 kJ/kg versus 8.6/k for the P20Z emulsion. The storage capacities and temperature ranges for the emulsions, calculated according to methods a-d, are shown in Figure 7 and listed in for method a and b in Table 3 and and for method c and d in Table 4. As expected, the larger the chosen temperature range, the more storage capacity is available, except for the analyses considering a 6 K temperature difference and taking the crystallisation curves into account according to method c. These analyses revealed a much lower storage capacity, as expected from the enthalpy change of the melting curve. Here, those materials with a high degree of supercooling show the lowest storage capacity. The comparisons of the storage capacities with those that would be obtained using water as the storage medium are shown in Figure 8. Here, a massive reduction of the benefits due to the supercooling phenomena and due to broad-phase transition temperature ranges is visible. The analyses that take only the melting curves into account (method a) show the maximum possible SF operating a system at the phase  
Figure 4: Degree of supercooling and onset temperature of melting for the different emulsions. transition from a solid to liquid without any supercooling. Considering only the melting curve with a temperature range of 6 K (according to method b), the benefit is reduced for all materials but shows the realistic maximum benefit compared to water as the storage material in a real storage application. With the given supercooling and melting, as well as crystallisation ranges, P20Z, P19-97 and P17-97 perform best with a SF around 2.5. Considering the 6-K limit according to method c, RT27 offers a 1.8 higher SF than P18-97. Using the full temperature range (method d), P18-97 shows with 2.22 versus 2.06 (RT27) a 7.8% higher SF. Figure 5: Enthalpy curves of the PCM emulsions with a PCM fraction of 35 wt.% each. For each curve, the enthalpy is set to 0 at T\({}_{\text{m-end}}\). Figure 6: Enthalpy curves for the P16-97/P18-97, L17 and P17-97 emulsions. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Sample**} & \multicolumn{6}{c}{**Based on the Melting and Cryst. Curve,**} & \multicolumn{6}{c}{**Based on the End of Melting and End of Crystal.**} \\  & \multicolumn{6}{c}{**dT 6K (c)**} & \multicolumn{6}{c}{**Curve (d)**} \\ \cline{2-9}  & \(\mathbf{T_{c-c\text{-}6K}}\) & \(\mathbf{\Delta T_{load}}\) & \(\mathbf{\Delta H_{c-m\text{-}6K}}\) & **SF** & \(\mathbf{T_{c-c\text{-}}}\) & \(\mathbf{\Delta T_{load}}\) & \(\mathbf{\Delta H_{m\text{-}c\text{-}c\text{-}c\text{-}}}\) & **SF** \\ \hline  & \({}^{\circ}\mathbf{C}\) & **K** & **kJ/kg** & **-** & \({}^{\circ}\mathbf{C}\) & **K** & **kJ/kg** & **-** \\ \hline P16-97 & 12.2 & 6 & 20.9 & 0.73 & 8.2 & 10.00 & 96.29 & 2.01 \\ P16-97/P18-97 & 15.5 & 6 & 60.8 & 2.11 & 14.7 & 6.77 & 76.92 & 2.37 \\ L17 & 15.7 & 6 & 51.96 & 1.81 & 13.8 & 7.88 & 85.18 & 2.25 \\ P17-97 & 15.9 & 6 & 62.88 & 2.19 & 15.3 & 6.62 & 81.79 & 2.58 \\ RT27 & 20.5 & 6 & 53.66 & 1.87 & 19.4 & 7.06 & 69.72 & 2.06 \\ P18-97 & 21.6 & 6 & 40.03 & 1.39 & 20.0 & 7.62 & 81.06 & 2.22 \\ P19-90 & 26.0 & 6 & 81.83 & 2.84 & 25.4 & 6.60 & 86.51 & 2.73 \\ P19-97 & 26.4 & 6 & 70.13 & 2.44 & 25.3 & 7.02 & 82.82 & 2.46 \\ P20Z & 30.0 & 6 & 68.95 & 2.40 & 29.6 & 6.46 & 74.57 & 2.41 \\ \hline \hline \end{tabular}
\end{table}