  In highly renewable power systems the increased weather dependence can result
in new resilience challenges, such as renewable energy droughts, or a lack of
sufficient renewable generation at times of high demand. The weather conditions
responsible for these challenges have been well-studied in the literature.
However, in reality multi-day resilience challenges are triggered by complex
interactions between high demand, low renewable availability, electricity
transmission constraints and storage dynamics. We show these challenges cannot
be rigorously understood from an exclusively power systems, or meteorological,
perspective. We propose a new method that uses electricity shadow prices -
obtained by a European power system model based on 40 years of reanalysis data
- to identify the most difficult periods driving system investments. Such
difficult periods are driven by large-scale weather conditions such as low wind
and cold temperature periods of various lengths associated with stationary high
pressure over Europe. However, purely meteorological approaches fail to
identify which events lead to the largest system stress over the multi-decadal
study period due to the influence of subtle transmission bottlenecks and
storage issues across multiple regions. These extreme events also do not relate
strongly to traditional weather patterns (such as Euro-Atlantic weather regimes
or the North Atlantic Oscillation index). We therefore compile a new set of
weather patterns to define energy system stress events which include the
impacts of electricity storage and large-scale interconnection. Without
interdisciplinary studies combining state-of-the-art energy meteorology and
modelling, further strive for adequate renewable power systems will be
hampered.
