Climate-driven compounding effects and historical trends in renewable electricity droughts in Europe

In the interconnected European power system, renewable electricity droughts (REDs)—periods of unmet demand by renewables—may be triggered by weather-driven compounding effects of high demand and low generation from wind, solar, and/or run-of-river hydropower, particularly when simultaneous REDs compound across multiple regions. Yet, our understanding of such compounding effects and historical trends in REDs, remains limited. We study REDs using weekly electricity generation and demand from 1941 to 2023 derived via the PyPSA-Eur framework, focusing on the season most affected by REDs and, to isolate climate-driven impacts, assuming fixed present-day installed generation capacities. Across nine European macro-regions, each comprising highly interconnected small-scale areas, REDs are mainly driven by wind generation and demand, with prominent compounding effects in central Europe, Italy, and across the UK and Ireland. Wind-demand correlations enhance REDs in central and northern Europe but weaken them in the south. Furthermore, macro-regional REDs primarily occur due to simultaneous REDs in small-scale areas. In an increasingly interconnected continental power system, we find that correlations between residual loads of macro-regions increase the probability of simultaneous macro-regional REDs, ultimately intensifying Europe-wide REDs by 40 % on average compared to a scenario without correlations. Finally, we assess weather-driven trends in REDs, finding that increasing temperatures lowered winter heating demand and thus reduced RED frequency, while changes in correlations between demand and generation sources, along with between residual loads across macro-regions, amplified Europe-wide RED risk. This research underscores the importance of considering compound effects between demand and generation across regions, along with long-term climate change, to optimize power systems.