Assessment of energy storage systems for renewable energy integration

The rapid expansion of wind and solar generation has created a structural need for flexible resources capable of providing firm capacity, frequency regulation and long-duration balancing. Energy storage systems are central to addressing these challenges, yet the diversity of technologies and metrics complicates technology choice for planners and regulators. This article develops a multi-criteria framework for the assessment of energy storage systems used to integrate variable renewable energy sources. The framework combines technical performance, economic efficiency and system-level contribution to renewable energy integration, including indicators such as round-trip efficiency, levelized cost of storage, discharge duration, renewable curtailment reduction and contribution to peak load coverage. It is applied to a set of stylized but empirically grounded power system configurations representing high wind, high solar and hydro-moderated structures. The results highlight the complementary roles of short- and long-duration storage and provide guidance for portfolio design and policy support instruments.