Advancing solar and wind penetration in China through energy complementarity

The intrinsic variability of solar and wind energy, compounded by their rapid expansion, has intensified power curtailment challenges^1,2. Although spatiotemporal complementarity between these resources is widely recognized as a pathway to enhance renewable integration and reduce balancing requirements^3-16, existing assessments are largely based on hypothetical deployments^17-24. Consequently, how solar-wind complementarity manifests under real-world infrastructure and shapes system-level integration outcomes remains unclear. Here we develop a unified national inventory to enable a data-driven assessment of solar-wind complementarity. The inventory covers 319,972 solar photovoltaic facilities and 91,609 wind turbines in 2022, identified from sub-metre satellite imagery using a deep-learning-based framework. Using this dataset, we show that solar-wind complementarity substantially reduces generation variability, with effectiveness increasing as the geographic scope of pairing expands. At the system level, nationwide inter-provincial coordination raises effective renewable penetration by 99.88 TWh in an 80% dispatchable-flexibility system, corresponding to 9.1% of total solar and wind generation, or approximately 120 h of national average load. These findings demonstrate that energy complementarity is a scalable, system-wide mechanism for advancing solar and wind penetration, offering broadly applicable insights into the role of inter-regional coordination in enhancing renewable integration in large power systems.