The generation of wind energy depends to a significant extent on the changing weather conditions. This is why the yield from wind energy plants and farms fluctuates year-on-year. To ensure economic operation, it must be clarified whether the full potential output over the course of the year was achieved or reduced as a result of disruptive influences such as shadowing and sub-optimal plant operation. For a number of years now indexes have been used for onshore plants in Germany which allow the achieved wind farm output to be compared against the expected output. On the basis of this, operators can identify and remedy the causes of performance losses and thus increase profitability. The “Offshore Wind Energy Index” (FROENIX) uses this enhanced methodology at offshore wind farms in the German Bight.
The Fraunhofer IWES Offshore Wind Energy Index (FROENIX) provides an opportunity to estimate the inter-annual power density variation at offshore wind farm sites. It reveals the percentage deviation of the average wind power density during one year compared to the average wind power density of the past 5 and 10 years. As such, it allows wind farm operators and owners as well as grid operators to assess their wind farms’ power output in comparison with the long-term average and to identify the causes of power losses.
The index is computed separately for each of the 13 offshore wind farm clusters (as defined in Bundesfachplan Nordsee 2012 (2012 Federal Plan for the North Sea)). It is calculated from more than a decade of mesoscale simulations of the wind conditions over the German Bight with a resolution of 30 minutes in time. The horizontal resolution of the simulations is 2.1 km. These data (time series, wind fields and statistics) can be made available on request. Furthermore, Fraunhofer IWES can also provide simulations which take the follow-on effects of large offshore wind clusters into account. The simulations did not take any wind farm effects within the German Bight into consideration. Consequently, the impact of the expansion of surrounding wind farms can be estimated by comparing the actual production data with the wind index data.
Fraunhofer IWES offers a wide range of services for the offshore wind energy industry. This includes energy yield and wind farm power performance assessments, offshore wind measurements, and numerical simulations of individual wind turbines, entire wind farms and even wind farm clusters, as well as large-scale tests of support structures and offshore construction methods.
Cluster evaluations for the years 2015 and 2014