Analysis of compound extreme weather events related to wind and solar power generation in Spain

The viability of low carbon power systems (LCPS) is becoming more realistic. However, such energy systems present serious challenges in becoming a reality. One of the most important problems is related to the inherent variability of renewable sources, which represent a risk for these systems. Although these systems may include methods to minimize these risks (backup plants, improved interconnection, etc.), these solutions may not be sufficient in extreme weather conditions, in particular, in the so-called compound extreme events. These events are characterized by the simultaneous occurrence of several hazards, generally associated with complex interactions between a wide range of meteorological processes acting on different temporal and spatial scales. In the context of LCPS analysis, compound events can be associated with periods with below normal solar and/or wind power generation and above normal demand. The occurrence of such events may overwhelm the capacity of LCOP systems in the future, thus causing socially significant impacts. In this work, the occurrence of compound extreme weather events related to wind and solar power generation in Spain are identified and the meteorological conditions that cause them described. The study is part of the MET4LOWCAR Spanish project, that aims at demonstrating the benefits of the design of the LCPSs that accounts for the regional weather and climatic patterns of both solar and wind renewable resources, using the Spanish territory as a testbed.

 

The study is carried out based on real data on daily demand, wind and solar generation provided by the Spanish TSO and corresponding to the 2008-2020 period. Three different types of events were analyzed: compound solar/wind events (below normal solar/wind and above normal demand) and compound solar and wind events (below normal wind and solar and above normal demand). Specific threshold were used to identify these events. The study is conducted using normalized time series, at different periods (1, 5 and 15 days) and separately for each season of the year. The weather patterns associated with the compound events were analyzed using composite analysis by means of ERA-5 reanalysis data.  Results showed firstly, that while compound events are relative frequent for short periods (1 and 5 days), very long events (15 days) are much rarer. In addition, a marked seasonality of the events occurrence is observed, with a peak during the winter season. It was also found that compound event related to wind power generation anomalies are more frequent and intense. Many events were found associated with the presence of negative/positive centers of geopotential heights anomalies roughly located over Portugal/Great Britain, although the intensity and location of the centers varies along the year. Finally, some conclusion regarding the optimal design of a reliable LCPS for Spain are derived and discussed.