Strategic site-level planning of VRE integration in hydro-wind-solar systems under uncertainty

The rapid expansion of variable renewable energy (VRE) sources such as wind and solar, driven by global decarbonization efforts, necessitates innovative strategies to address their intermittency. Hydropower stations, with inherent operational flexibility, can help balance VRE intermittency. The development of hydro-wind-solar (HWS) energy bases is a growing trend to enable the grid integration of large-scale wind and solar power stations. However, existing HWS planning models often oversimplify VRE output characteristics, neglecting spatial heterogeneity. Furthermore, these models mostly rely on deterministic inputs, overlooking uncertainties. To address these limitations, we introduce an integrated optimization framework that optimizes capacity mix at a site-specific spatial resolution, incorporating uncertainties from technological, climate, policy, and market changes. Applied to China's Yalong River HWS base, the framework results in a 7 % increase in economic benefits and an 18 % reduction in VRE capacity compared to models that ignore resource heterogeneity. Under varying conditions, cost-effective generation from the HWS system achieves over 80 TWh per year, representing 68 % of its total potential, with an optimal transmission line capacity of 12,375 MW. Additionally, the framework provides a robust development sequence for wind and solar power stations under uncertain futures. These results offer actionable insights for planning resilient HWS systems.