Analysis of synoptic conditions that lead to Energy Compound Events (ECEs) in the Portuguese electrical system, in current and future climates

This work is a multidisciplinary approach that analyzes the growing vulnerability of renewable energy production systems to climate variability dominated by just a few large-scale atmospheric regimes. In particular, the Portuguese electricity system is  heavily influenced by atmospheric vulnerability, due to its current high dependance on solar and wind energy, which increases the risk of energy shortages as a consequence of poor meteorological conditions, particularly in situations of low production and high demand. These episodes, known as energy compound events (ECEs), compromise the security and stability of the Portuguese energy system.

The main objective is to investigate the relationship between ECEs and large-scale atmospheric patterns, as well as to assess their evolution in the context of climate change. The methodology is structured in three phases: i) defining and characterizing ECEs in the Portuguese electricity system; ii) identifying the meteorological patterns associated with these events; and iii) assessing the impact of climate change on the frequency and intensity of these patterns. To this end, data on national electricity demand and solar energy production for the period 1989-2025 were obtained from the energy dataset of the European Copernicus Climate Change Service (C3S, https://climate.copernicus.eu/). Wind energy production was calculated from the CERRA atmospheric wind speed fields at 10 meters. The meteorological regimes affecting the Portuguese energy system were calculated from the 500 hPa geopotential height of the ERA5 database, based on the decomposition of the daily Z500 into empirical orthogonal functions and their grouping using k-means clustering. Finally, data from 14 global climate models (GCMs) obtained from the CMIP6 ensemble were used to analyze the evolution of the frequency and intensity of the identified regimes, as well as their consistency with the ERA5 observations (during the historical period) and in the future using different climate scenarios.

From the analysis, six meteorological regimes were identified as having an impact on renewable energy production in Portugal. Out of the 234 ECEs detected throughout the period, 144 occurred under the predominance of the positive phase of the North Atlantic Oscillation (NAO+), indicating an important contribution for ECEs occurrence. It is expected that the analysis of future projections will enable a robust assessment of the evolution of ECE risk in a constantly changing climate, contributing to adaptation and mitigation strategies and ensuring the reliability of energy systems.

 

This work is supported by FCT, I.P./MCTES through national funds (PIDDAC): LA/P/0068/2020- https://doi.org/10.54499/LA/P/0068/2020 , UID/50019/2025,  https://doi.org /10.54499/UID/PRR/50019/2025 ,UID/PRR2/50019/2025

This work has also received funding from the European Union’s Horizon 2.5 – Climate Energy and Mobility programme under grant agreement No. 101081661 through the 'WorldTrans – TRANSPARENT ASSESSMENTS FOR REAL PEOPLE' project