Beyond flexible regulation: building resilient renewable power system through spatiotemporal complementarity of wind-solar power

Wind-solar power is a pillar of renewable energy transition and climate mitigation. However, intrinsic volatility threats electricity supply reliability, which could be further jeopardized by projected climate change. Complementarity of wind-solar power has been introduced to suppress this volatility.  However, it has not been translated into a formal mathematical objective in optimization models. Especially, influences of considering complementarity on cost-effectiveness and supply reliability during long-term operation remains unknow. Here, these knowledge gaps are closed through developing a Daily Complementarity Index of wind–solar generation (DCI) and a nuanced analysis. The results of the comparison of our index with existing indices and site validation con-firm the reasonability of the DCI and its improvements in interpretability. Further, although introducing complementarity into the objectives could increase total initial invest, considering gains from declined supply shortage, increase in initial cost could be offset by effectiveness of trans-regional interconnection in enhancing supply reliability.