Climate-driven evolution of global wind-solar complementarity for hybrid energy systems (1940–2024)

This study examines the long-term climate-driven trends in global wind-solar power complementarity from 1940 to 2024, employing the ERA5 reanalysis dataset to evaluate wind power density (WPD) and solar power density (SPD) dynamics. Advanced statistical methods, including the Mann-Kendall test, Theil-Sen estimator, Spearman's rank correlation coefficient (SRCC), composite variability index (CVI), and K-means clustering, were utilized to analyze spatiotemporal patterns and their implications for hybrid renewable energy systems. The results indicate a significant global WPD increase of 0.66 ± 0.06 W/m2 per year, with notable enhancements in the Southern Ocean (+18 W/m2 per year, 1998–2024) and North Atlantic (+10 W/m2 per year), contrasted by a decline in the equatorial Pacific (−20 W/m2 per year, 1998–2024). SPD exhibits a historical decline of −0.038 W/m2 per year (1940–2009) due to global dimming, followed by an increase of 0.054 W/m2 per year (2010–2024) driven by global brightening. Seasonal complementarity analyses reveal strong anticorrelation in the North Atlantic and Southern Ocean during DJF (CVI: 0.52–0.76, SRCC: −0.4 to −0.7), while equatorial regions display synchronized variability (CVI: 0.88–1.0). The Northern Hemisphere (NH) exhibits the strongest complementarity in JJA (CVI: 0.8221, SR: 8.90 %), and the Southern Hemisphere (SH) in DJF (CVI: 0.8922, SR: 5.39 %). K-means clustering categorizes regions into four classes, identifying Class 1 regions (e.g., Northern Europe, India, Brazil, North Atlantic, Southern Ocean) as optimal for hybrid systems, reducing relative storage needs by up to 8.90 % (when compared to a baseline scenario with no complementarity) and unmet demand hours by 20 %. Conversely, Class 4 regions (e.g., Southeast Asia, Central Africa, Central Pacific) exhibit minimal complementarity, necessitating substantial storage solutions. These findings highlight the critical role of wind-solar complementarity in enhancing energy resilience, providing a robust foundation for strategic planning of sustainable energy systems under evolving climate conditions.