Wind droughts, or prolonged periods of low wind speeds, pose challenges for electricity systems largely reliant on wind generation. Using weather reanalysis data, we analyzed the global distribution of and trends in wind droughts using an energy deficit metric that integrates the depth and duration of wind droughts. We identified regions with high power densities, low seasonal variability, and limited weather fluctuations that favor wind power generation, such as the American Midwest, Australia, the Sahara, Argentina, Central Asia, and Southern Africa. Northwestern Europe has high power densities but experiences more frequent and prolonged wind droughts due to higher weather variability. We found little evidence for strong trends in wind droughts over recent decades in most places. Rather, the most severe wind droughts in many places occurred before wind power substantially penetrated power systems, which suggests that historical weather data can be useful in designing reliable wind-reliant electricity systems.

Renewable energy is essential for power system decarbonization, but extended and unexpected periods of extremely low wind and solar resources (i.e., wind and solar droughts) pose a threat to reliability. The challenge is further exacerbated if shortages of the two occur simultaneously or if they affect neighboring grids simultaneously. Here we present a framework to characterize these events and propose three metrics to comprehensively assess renewable energy quality: resource availability, variability, and extremeness. An examination of long-term data across a vast geographical region shows a strong spatial correlation and temporal coincidence of renewable energy droughts. It also finds a lack of sites that excel in all three quality attributes, which presents a trilemma to investors, system planners, and policymakers. These findings underscore the significance of considering factors beyond mere resource availability and contribute to developing informed strategies for the reliable and sustainable deployment of variable energy resources.