Investigation of low wind events over Germany from high resolution regional climate models

Wind energy has become one of the most important mitigation options for climate change over the last decades. However, variability and availability of wind are also expected to be changed due to climate change. For this purpose, the KliWiSt project has been initiated to determine the influence of climate change on wind energy site assessments in Germany. Within the scope of the project, many aspects of climate change impacts on wind energy have been studied to determine uncertainties about the topic and to develop recommendations for actions. Although there are many studies in literature which evaluate the effects of climate change on wind in the upcoming decades, low wind events are scarcely investigated so far. However, low wind events pose a risk for achieving long term renewable energy targets and ensuring stability of the electricity grids. Wind drought is increasingly becoming a significant phenomenon which determines low wind energy production due to extreme low wind resources.

In this study, we have investigated the frequency of low wind events in Germany due to climate change until the end of the 21st century by using an ensemble of high-resolution regional climate model simulations available from the EURO-CORDEX initiative. We also evaluated the performance of the regional climate models with data from different observation stations and with re-analysis data sets. For our investigation we used thresholds of 2 m/s and 3 m/s for wind speed at 10 m and 100 m – respectively for – calculating “calm wind” climate indices. The threshold is determined as 3 m/s (at 100 m height) for low wind events since most of the wind turbines starts wind energy production at this value (“cut in” wind speed). We used two different benchmark data sets (ERA5 and CERRA) to determine historical variation of “calm days” over Germany and to evaluate the performance of the high-resolution regional climate models. Moreover, seasonal, annual, and spatial distributions of low wind events are investigated for Germany where the country has already a high installed wind energy capacity and ambitious renewable energy targets. The study aims to determine trend and frequency of low wind events in the past and future at different terrain conditions at different time scales from different regional climate models. The anticipated results of the study and the project are expected to give insight for policy makers and stakeholders from the renewable energy sector.* 

*This study is part of the project "The influence of climate change on wind energy site assessments (KliWiSt)" which is funded by the German Federal Ministry for Economic Affairs and Climate Action (BMWK).