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Modeling Wind–Solar Complementarity under Heatwave Conditions: A Copula-Based Study for Southern Spain

Tuany Esthefany Barcellos(1); Daiane Rodrigues dos Santos(2); Marco Aurélio Sanfins(3)

1. Management Department, Estácio de Sá University, Rio de Janeiro (Brazil)
2. Department of Economics, State University of Rio de Janeiro, Rio de Janeiro (Brazil)
3. Department of Statistics, Fluminense Federal University, Rio de Janeiro (Brazil)

2026-06-27

The increasing penetration of variable renewable energy sources has raised critical challenges for power system planning, particularly under extreme climatic conditions. In Southern Europe, heatwaves have become more frequent and intense, with the potential to alter the joint behavior of wind and solar power generation. This study investigates how heatwave conditions affect the dependence structure between wind and solar generation in the Andalusia region of Spain using a copula-based modeling framework. Monthly aggregated wind and photovoltaic solar generation data from January 2015 to November 2025 are combined with climatic information from the ERA5 reanalysis dataset. Heatwave months are identified using a climatological threshold based on the 90th percentile of monthly mean temperature. Marginal distributions are selected through goodness-of-fit tests, and the joint dependence structure is modeled using bivariate copulas estimated by maximum likelihood and selected via the Bayesian Information Criterion. The results indicate weak negative dependence between wind and solar generation in the baseline scenario, suggesting moderate complementarity on average. However, this structure changes substantially when conditioning on heatwave occurrence: months without heatwaves exhibit near independence between sources, whereas heatwave months display a stronger negative dependence, captured by a rotated Clayton copula. Scenario simulations further show that heatwaves reshape the joint distribution of renewable generation, reinforcing complementarity under extreme thermal conditions. These findings highlight the importance of incorporating climate extremes into multivariate renewable energy modeling and provide relevant insights for energy planning and risk assessment in regions increasingly exposed to heatwaves.

Key words: Wind–solar complementarity; Heatwaves; Copula models; Renewable energy systems

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