Integrated Procurement Strategies for Corporate Renewable Electricity: Combinations of Direct PPA, Energy Storage, and Market Participation

As corporates increasingly pursue ambitious Renewable Energy (RE) 100 targets, establishing economically viable renewable electricity procurement strategies has become essential. In this context, this study proposes a framework for optimizing corporate electricity procurement strategies by jointly considering Direct Power Purchase Agreements (PPAs), wholesale electricity market purchases through the Korea Power Exchange (KPX), and energy storage system (ESS) operation. A mixed-integer linear programming (MILP) model is developed to minimize the total annual electricity procurement cost of industrial consumers while satisfying RE usage targets under the regulatory structure of the Korean electricity market. Using an industrial load case, the analysis evaluates optimal PPA contract capacity and ESS sizing under varying RE targets, PPA contract prices, and system marginal price scenarios for 2024–2025. The results show that Direct PPA–based procurement becomes infeasible without ESS beyond an RE target of approximately 20%, while nonlinear growth in ESS capacity requirements drives a sharp increase in procurement costs beyond approximately 80% renewable penetration. By comparison with the Green Premium–based strategy, the proposed strategy can become more cost-competitive and more effective in enabling corporates to achieve substantive RE100 targets when lower PPA contract prices and higher ESS subsidy levels are secured.