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Orsted says Irish Sea is full
Wind turbines extract kinetic energy from the air to produce electricity. When they do this, they leave trails of slower and more turbulent wind stretching behind them. These trails, known as wind wakes, can stretch vast distances – even 100km. If one wind farm is caught in the ‘shadow’ of another’s wake, the slower wind speed will mean it generates less power. One wind farm ‘waking’ another is sometimes known as ‘wind theft’.
Credit: "Orsted warns Miliband ahead of ruling that could doom its Irish Sea wind farms" | Cosmo Sanderson | Published 4 June 2025 | rechargenews.com ~~
Orsted has warned UK energy secretary Ed Miliband that its Irish Sea offshore wind assets could be shuttered a decade earlier than otherwise if he makes an “essentially irreversible” ruling against it in its wind theft dispute with EnBW and BP.
The Danish renewables giant has been caught up in various disputes with developers of new offshore wind farms, arguing that wind wakes they will generate will act as a wrecking ball to the economics of its existing assets in UK waters.
Equinor and SSE each own 40% stakes in the three 1.2GW Dogger Bank projects, with Norway’s Vargronn holding the remainder.
Its latest warning to Miliband came in the planning proceedings for the 1.5GW Mona project being developed in the Irish Sea by British oil major BP and German utility EnBW.
The examining authority in that proceeding issued its recommendation to Miliband on granting it a development consent order in January. Last month, Miliband asked for more information from the developers in several issues, including wind wakes.
BP and EnBW are currently seeking consent orders for Mona and a twin 1.5GW project, Morgan, in the Irish Sea. The 480MW Morecambe project, recently acquired by Copenhagen Infrastructure Partners, is also seeking such an order. German utility RWE secured an order for its up-to-1.1GW Awel y Mor project in 2023.
Orsted owns 1.85GW of operational wind farms in the Irish Sea. That includes the Barrow (90MW), Burbo Bank (90MW), Burbo Bank Extension (256MW) and West of Duddon Sands (389MW). Its four-part Walney wind farm and extension boast just over a gigawatt of capacity.
Orsted has previously submitted a wake loss assessment that found the four new wind farms being developed would cause its Irish Sea assets to collectively suffer wake losses of 3.8%. Those losses could stretch up to 5.3% for individual projects, a level labelled “catastrophic” by one analyst.
In a submission late last month in response to Miliband’s request, Orsted warned that the modelled wake losses are so severe that they could lead to it not seeking lifetime extensions for its Irish Sea wind farms.
Orsted says that based on its extensive experience and assessment of the assets, it believes that its 1.8GW of assets near Mona could have their lifetimes extended a decade beyond their 20–25-year certified design life.
But if wake effects are not mitigated or compensated, it “could be sufficient to tip the scale in favour of decommissioning the assets.”
A map of the existing and planned wind farms in the Irish Sea, with Orsted’s assets circled in blue and Morgan, Mona and Morecambe in red.
Once the consent order for Mona is granted, Orsted said it will reflect associated wake losses in its projects’ financial forecasts and adjust commercial decisions regarding lifetime extension accordingly. “Therefore, if no mitigation for wake effects is provided, those effects are essentially irreversible.”
Orsted urged that this “worst-case scenario” where a decade of life is effectively lost from these assets must be considered in calculations submitted by BP and EnBW for Mona on the effect the project will have on greenhouse gas emissions.
Currently, it said this note “ignores the potential” for Orsted assets to continue operating “beyond their initially anticipated lifetimes.”
Miliband has backed Orsted in one decision in the proceeding, ruling – preliminarily at least – that BP and EnBW should carry out their own assessment of how much wake losses from their project will affect the Orsted assets.
Low hanging fog reveals what is usually invisible to the eye, wind wakes stretching behind a wind farm in the North Sea.
BP and EnBW pushed back on that in their own submission late last month, arguing that a requirement to do this cannot be found in the relevant policy statements.
The developers insist that it is not possible to carry out a robust assessment of these wake effects and that the effects are “substantially mitigated” by the distance between the projects. They also argue that any mitigation solutions, such as rearranging turbines at Mona, will have a negative overall effect on overall carbon reduction.
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