## 2 Benefits Assessment of ESS Introduction in the F/R Market
### Long-Term SMP Forecasting of the South Korean Electricity Market  
We conducted a case study to investigate UBs and examine how ESS for F/R affects efficiency in South Korea. To undertake this investigation, we must first estimate the SMP according to the method proposed in Section 2.1. First, we considered the auxiliary power consumption ratio, the FOR, and the MOR to determine the actual supply capacity; this was obtained by deducting these rates for each of the generation resources. We assumed that the auxiliary power consumption ratio was 5%; additionally, for FOR and MOR, we used the average from the 2014-2015 period (Table 2). By substituting these figures and applying the renewable energy availability in resource capacity [24], we can determine the actual supply capacity and generation mix. The generation mix of the base load is based on the constructed actual supply capacity (Table 3). As part of the renewable energy penetration policy, the capacities of nuclear and coal resources will be reduced, while those of renewable energy resources will be increased. According to the national plan [24], renewable resources consist of photovoltaic power, wind power, tidal power, and by-product gas. Once we estimate the actual supply capacity, we can then estimate the annual demand on weekdays and weekends and compare these values to the actual supply capacity. Demand is estimated based on [24], and we use weekday and weekend patterns from 2016 to estimate the annual demand pattern ratio for 24 h; future demands are projected using the annual electricity consumption projection of [24], based on the load-pattern ratio. The hourly load profiles of weekdays and weekends, which are estimated as the average of the 2016 electricity load, are illustrated in Figure 4. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Resources**} & \multicolumn{2}{c}{**Nuclear**} & \multicolumn{2}{c}{**Coal**} \\ \cline{2-5}  & **FOR** & **MOR** & **FOR** & **MOR** \\ \hline
2014 & 1.35\% & 15.69\% & 0.30\% & 7.56\% \\
2015 & 1.96\% & 14.45\% & 0.30\% & 8.57\% \\ Average & 1.67\% & 15.07\% & 0.30\% & 8.06\% \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Average forced outage rate (FOR) and maintenance outage rate (MOR) values of South Korean nuclear and coal power plants. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multicolumn{1}{c}{**Year**} & **Renewable** & **Nuclear** & **Coal** \\ \hline
2019 & 3704 & 20,712 & 34,121 \\
2020 & 4045 & 20,712 & 35,305 \\
2021 & 4398 & 20,712 & 37,796 \\
2022 & 4756 & 21,825 & 39,813 \\
2023 & 5117 & 22,422 & 39,813 \\
2024 & 5799 & 21,666 & 38,752 \\
2025 & 5799 & 21,666 & 38,752 \\
2026 & 6691 & 18,844 & 37,805 \\
2027 & 7191 & 17,532 & 37,805 \\
2028 & 7699 & 16,561 & 34,559 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Actual supply capacity of renewable, nuclear, and coal resources, 2019–2028 (Unit: MW). We assume that the 2019-2028 load patterns are similar to the 2016 load patterns. To estimate the 2019-2028 load profile, the load-pattern ratio was obtained by dividing the load profile by the load profile peak demand. Annual peak load was calculated from the electricity consumption and the sum of the load-pattern ratio for 24 h (Table 4). We were then able to estimate the annual load profile of weekdays and weekends for the 2019-2028 period. Following our 2019-2028 load profile estimation, we verified which resource would be selected in each hour by comparing the load profile and generation mix. Figure 5 shows the weekday and weekend load profiles, as well as generation, in 2024. Renewable resources do not comprise a single resource; rather, they are derived from multiple sources. Nonetheless, the national plan does not provide planned capacity for each type of renewable resource. This means that we encountered difficulties in generating actual hourly generation projections for renewable resources. Therefore, despite the inherent flexibility, we assumed that the single renewable resource is constant over time.