Techno-Economic and System-Level Evaluation of PV-Integrated Energy Storage Systems for High Renewable Penetration Grids

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Energy Storage Systems (ESS) are increasingly recognized as critical enablers of grid flexibility in power systems with high renewable energy penetration. This study presents a comprehensive techno-economic and system-level evaluation of a photovoltaic (PV)-integrated ESS operating under grid-connected and emergency modes. Unlike prior studies that focus primarily on conceptual or policy perspectives, this work integrates operational modeling, economic feasibility analysis, and national-level storage sizing considerations within a unified framework. At the project level, a 5 MW / 20 MWh commercial-scale ESS operating under time-of-use (TOU) pricing was evaluated. An arbitrage-only operation yielded an internal rate of return (IRR) of 7–9% and a payback period of approximately 10–11 years, indicating marginal yet feasible profitability under current tariff spreads. When multi-service revenue stacking—incorporating frequency regulation, reserve provision, and peak shaving—was applied, IRR improved to 11–14%, and the payback period decreased to 7–8 years. Sensitivity analysis confirmed that a 30% reduction in battery capital costs is the dominant factor affecting economic viability, with an IRR above 15%. Operationally, annual simulations of the PV–ESS system demonstrated a round-trip efficiency of approximately 87%, a 20% reduction in peak demand, and emergency autonomy exceeding the required 2-hour duration.