The probability of long phases without wind power and their impact on an energy system with high share of renewable energies

Long phases of no or little wind power are a potential thread to future energy systems with a high share of renewable energies. A frequently cited example observed in Germany was a whole week with very little wind power due to temperature inversion in January 2009. A frequent occurrence of these and similar situations would imply an increased need for energy storage or controllable power capacities in order to cover energy demand at any time in future energy systems. Energy system research analyses the future effect of high renewable feed-in using mainly historical weather or renewable energy feed-in time series data. However, an understanding of the representativeness with respect to extreme weather events and long phases of low wind speeds or calms is still limited. Here, we study the frequency of occurrence of long calms in wind power feed-in and residual load as well as differences in their frequency of occurrence between different years. We analyse seven years of aggregated wind power feed-in in Germany on an hourly basis. We discuss the occurrence of extreme events in low wind and renewable power feed-in as observed historically for different threshold levels of low feed-in. In addition to this, we use extreme value statistics to obtain reliable estimates for extreme events such as hundred year calms. We find the average duration of low wind power feed-in phase to grow linearly with the threshold: Phases with a wind power feed-in of less than two percent of installed power are typically four hours long and phases with less than five percent feed-in are on average seven hours long. However, a period of wind power feed-in below eight percent of installed power that lasts one week occurs every two years and a period of more than ten days occurs every ten years.