Evaluation of reanalyses for onshore wind energy applications in Germany

In 2023, renewable energies contributed to 56% of the total electricity production in Germany. A further increasing of this percentage is expected in the near future due to rising number of wind and solar power installations. Their production is closely intertwined with climatological conditions and tied to local meteorological conditions.

In order to estimate and investigate potentials for the generation of these renewable energies’, consistent datasets on a climatological scale are required. In recent years, reanalyses have proven to be a reliable source providing long-term consistent meteorological data sets for use in the energy sector. For such applications Germany's National Meteorological Service (Deutscher Wetterdienst, DWD) currently produces a new regional reanalysis product, the “COSMO-REA6 Generation 2” (COSMO-R6G2). The new data set is a successor of the well-known COSMO-REA6 reanalysis (developed by DWD in cooperation with the universities of Bonn and Cologne within the Hans-Ertel-Centre for Weather Research of DWD), but using ERA5 instead of ERA-Interim as boundary conditions. COSMO-R6G2 will cover the period from 1995 to present, retaining the spatial and temporal resolution of COSMO-REA6.

A systematic quality assessment is required before the data set is applied in energy-related projects of the DWD and released to the public.

For example, DWD is involved in the ‘Network of Experts’ of the German Ministry of Digital and Transport (BMDV), where the energy potential in the German transport infrastructure is analysed. Another example is the project MEDAILLON (supported by the Ministry of Economic Affairs and Climate Action (BMWK)), which aims to provide datasets for energy system research).

This contribution focuses on the evaluation of wind speed and direction at typical hub height of wind turbines of about 100 m a.s.l. over the German land area. The quality of different reanalyses and derived data sets for national offshore wind applications has recently been demonstrated by Spangehl et al., 2023 (https://doi.org/10.5194/asr-20-109-2023). To assess the usability for onshore wind energy applications we compare R6G2 wind fields to ground-based LIDAR measurements and wind measurement masts in Germany. Moreover, we compare the performance of COSMO-R6G2 compared to other reanalysis data sets, e.g. ERA5, COSMO-REA6 to identify potential improvements such as the more realistic representation of the diurnal cycle.