## 5 Result of Simulation
### Result and Discussion of Each Scenario  
This section compares the battery aging results under each scenario, discussing the relationship between the capacity fade behavior and the system conditions, including the frequency regulation service mode, the rated power, and the storage capacity. Table 3 shows the detailed information of the comparisons.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Scenario** & **Mode** & **Spec. of BESS** & **SOC Level Target** \\ \hline
1 & dReg0.5 & 5 MW/6.25 MWh & 70\% \\
2 & dReg0.5 & 5 MW/6.25 MWh & 50\% \\
3 & dReg0.5 & 5 MW/6.25 MWh & 30\% \\
4 & dReg0.5 & 5 MW/3.125 MWh & 50\% \\
5 & dReg0.25 & 5 MW/6.25 MWh & 50\% \\
6 & dReg0.25 & 5 MW/3.125 MWh & 50\% \\
7 & sReg & 5 MW/6.25 MWh & 90\% \\
8 & sReg & 5 MW/12.5 MWh & 90\% \\
9 & sReg & 5 MW/6.25 MWh & 70\% \\ \hline \hline \end{tabular}
\end{table}
Table 2: Specification of simulation scenarios.  
Figure 12: A schematic diagram for mapping superposition.  
\begin{table}
\begin{tabular}{c c c} \hline \hline  & **Battery Life Comparison** & **Scenarios for Comparison** \\ \hline A & dReg0.5 with different SOC level targets & 1,2,3 \\ B & dReg under different C-rates & 2,4(dReg0.5) \\ C & dReg0.5 and dReg0.25 under the same spec. & 2,5 \\ D & sReg under different C-rates & 7,8 \\ E & sReg under different SOC level targets & 7,9 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Overview of comparison between scenarios.  
Figure 13: The result under different SOC levels (dReg0.5).  
dReg0.25 and dReg0.25 with the same rated capacity and battery energy:  
Scenario 2 and Scenario 5 were dReg0.5 and dReg0.25 at 5 MW/6.25 MWh, respectively, with the results shown in Figure 17. In this case, it can be estimated that for the energy  
Figure 16: The aging ratio of Scenarios 5 and 6.  
Figure 14: The aging ratio of Scenarios 1 to 4.  
Figure 15: The result under different C-rates using dReg0.5 and dReg0.25.  
storage system with the same rated capacity and the same total battery energy, the battery lifetime of dReg0.5 mode would be longer than that of dReg0.25.  
Compared with dReg0.5, dReg0.25 often needs to carry out more output outside the deadband, so the cycle depth of dReg0.25 is higher than that of dReg0.5 under the same frequency conditions. Therefore, the capacity fade rate caused by cycling aging of dReg0.25 is much faster than that of dReg0.5, which indirectly leads to dReg0.25 reaching the end of battery life faster.  
As shown in Figure 18, Scenario 8 with a lower C-rate did lived longer than with a higher C-rate (Scenario 7), but the difference was almost negligible. Considering the cost of installation, the total battery energy of Scenario 8 was twice that of Scenario 7, which may not be economical.  
As shown in Figure 19, in the scenarios of the sReg mode with the SOC level target at 90%, the proportion of calendar aging was significantly higher than that of cycle aging, especially in the case of Scenario 8, which almost dominated the battery life. Outputting the same power, the SOC variation of the scenario with a lower C-rate will be lower than  
Figure 17: The result under dReg0.5 and dReg0.25.  
Figure 18: The result under different C-rates (sReg).  
that of the one with a higher C-rate, so in the long run, the overall capacity fade caused by cycling aging will indeed be lower. However, as the proportion of cycling aging in these scenarios was not high, the effect of reduced cycle aging on the overall battery life was not significant.