System-level analysis of energy storage requirements for large-scale renewable integration

Driven by cost reductions, improved performance, and advancements in smart technologies, large-scale PV and wind integration is accelerating. This study develops a comprehensive modeling approach to investigate the complex interaction among key system parameters, including the PV-wind mix, storage, curtailment, and balancing capacity, using PVGIS and Global Wind Atlas-derived data for Eritrea, addressing a gap often overlooked in most energy transition models that prioritize economic data over such interactions. The goal is to develop design and operational guidelines that address rising uncertainties in renewable-dominated grids to maximize renewable integration in future power systems. Different storage technologies are deployed to handle the daily and seasonal mismatches. The results show that diurnal storage with a 0.16 average daily demand enables 80% penetration except for a few cases. In all tested scenarios, penetration increases sharply at lower storage levels but gradually slows and stabilizes beyond a certain threshold. Beyond 80% penetration, adding diurnal storage yields minimal gains, as small increases in penetration require disproportionately large diurnal storage or excess generation. However, adding seasonal storage, with about 8 average daily demand at a RE-to-load ratio of 1.2, enables full demand coverage without additional balancing capacity. To optimize the different parameters, the system-use-index introduced in our previous work is adopted. This index provides a holistic measure of system performance by linking system efficiency with other parameters, such as storage and curtailment, thereby enhancing system flexibility and reliability. These insights contribute to the development of scalable, flexible, and sustainable future energy systems.