Observing Wake Impacts in Offshore Europe: Part 1
With publicly available power data, we can get a key look on long-term energy production impacts.
As offshore wind expands in Europe, interfarm wake effects—where wind deficits emanating from one wind farm reduce the wind resource available to a neighboring farm—are becoming an increasing challenge, fueling a growing number of disputes. At the heart of these conflicts is the uncertainty around the magnitude of wake-induced losses, which remains difficult to quantify due to limited and often confidential wind farm energy production data. Publicly available datasets are crucial for addressing this gap, providing the transparency needed to assess wake impacts and inform future development decisions.
Enter two datasets: ENTSO-E 16.1.A power production dataset and Exelon B1610—both valuable public resources for analyzing offshore wind performance across Europe. ENTSOE-E 16.1.A is maintained by the European Network of Transmission System Operators for Electricity (ENTSO-E), it provides hourly power production data at the plant level going back as far as 2015, while Elexon is responsible for operating the Balancing and Settlement Code (BSC) in the UK electricity market. As part of this role, Elexon collects and publishes data related to electricity generation and consumption. Both datasets offer compelling data records back to 2015 that could be used to identify interfarm wake effects, provided skilled filtering of the data to account for other inherent losses in the data (availability, curtailment, etc.).
Our first case study is the combined Walney 1 and 2 wind farms (yellow outline), which since 2018 have been waked by the Walney Extension (red outline). A wind rose taken from Vortex FDC (top right of figure) shows predominant winds from the southwest direction. (Image courtesy of 4COffshore.)
To explore the efficacy of these data, we select the Walney 1 and 2 wind farms located off the coast of the UK in the Irish Sea. Commissioned in 2011 and 2012, the wind farms were impacted by the later introduction of the 659 MW Walney Extension in 2018. By combining the filtered power data with ERA5 reanalysis wind speeds, we were able to track long-term performance trends and quantify losses. The analysis reveals large differences between the two datasets. For ENTSO-E, we see the long-term Net Capacity Factor (NCF) of Walney 1 and 2 dropping from an average of 50.0%–51.5% before the extension to 41.5%–43.0% afterwards—indicating an estimated wake-induced loss of 14%–19%. The Exelon dataset, on the other hand, shows a drop from about 49-50% NCF to 44%, before recovering to about 46%, suggesting only a 6%–12% decrease.
Regardless of magnitude, we can't say for certainty that these losses was all caused by wakes. Reduced availability and higher curtailment post-extension could also play a role and may not have been adequately filtered. However, given the timing of the decrease, the role of Walney Extension seems clear.
Long-term trend in NCF for Walney 1 and 2 using the ENTSO-E data. The shaded red period marks the commissioning of the Walney Extension in 2018-09 which, based on the rolling 12-month calculation of NCF, begins to impact a year earlier in 2017-10. Note that data stopped reporting in 2021 after Brexit.
Same as figure above but using the Exelon B1610 database.
These findings highlight the significant impact of interfarm wakes on offshore wind production and underscore the value of publicly available power data in assessing real-world energy losses. To further validate this finding and demonstrate the broader utility of these datasets, we will extend our analysis to additional offshore wind farms across Europe. By examining a range of sites and conditions, we aim to build a clearer picture of wake interactions and provide actionable insights for developers, policymakers, and researchers navigating the challenges of offshore wind expansion.