摘要:Korea has been enforcing the environmental policies(ETS(Emission Trading Scheme), RPS(Renewable Portfolio Standard)) to reduce the greenhouse gas, and has been promoting the expansion of the ESS(Energy Storage System) supply through the K-ESS 2020 strategy. Accordingly, the role of the ESS in the power system has been attracting the recent interest and the effects are being verified. However, there is no standard for the optimal input capacity. It is rational to increase the ESS capacity as much as possible in order to optimize the proper function actualized by the ESS. However, since it is difficult to greatly increase the ESS capacity input as of this point due to high investment cost of the ESS, it is necessary to set up a standard for calculating the most economic input capacity. Accordingly, in this paper, in the process for establishing the generation plan, the environmental policies are considered into calculating the optimal fuel mix as well as the ESS optimal capacity per year.