‘Catastrophic’ wake losses threaten existence of Orsted Irish Sea wind farms

Danish developer owns 1.85GW of operational wind farms in Irish Sea but says wakes from planned projects could 'shorten life' of assets whose revenues would be hit

Orsted says that wake losses from offshore wind farms planned by EnBW, BP and RWE pose an existential threat to its Irish Sea assets, as a former project CFO at the Danish developer tells Recharge of the “catastrophic” impact they could have based on recent modelling.

An assessment commissioned by Denmark's Orsted has found that four planned wind farms in the Irish Sea could result in wake losses and a drop in annual energy production (AEP) of up to 5.34% for its operational assets nearby.  

Without adequate mitigation or compensation, Orsted said the new projects “threaten coexistence” with its wind farms.

In a submission filed on Monday, Orsted said that the "scale of impact is such that it could impact in a material way upon the life extension decisions in respect of the existing projects." There is it said a "material risk, given the scale of impact, that extensive years of generation could be lost entirely". 

Orsted is arguing this in planning proceedings for the twin 1.5GW Mona and Morgan offshore wind farms being developed by German utility EnBW and UK oil giant BP; and in that for the 480MW Morecambe project Copenhagen Infrastructure Partners recently bought from Cobra and Flotation Energy.

The fourth wind farm in question is the up-to-1.1GW Awel y Mor array, however RWE already secured a development consent order for that project in 2023.

What are wind wakes?

When wind turbines extract energy from the wind to produce power, they leave trails of lower intensity 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 lower wind speed will mean it generates less power, reducing revenues. One wind farm 'waking' another is sometimes known as ‘wind theft’.
Orsted owns 1.85GW of operational assets in the Irish Sea, including Barrow wind farm (90MW), Burbo Bank (90MW), Burbo Bank Extension (256MW) and West of Duddon Sands (389MW).

It also owns the Walney wind farm, which is broken down into four phases. The first two phases boast 184MW capacity and the second two – collectively known as the Walney Extension – can together produce up to 659MW of power.

Orsted has, as in several other planning applications for projects being developed in UK waters, lodged objections in the proceedings for Morgan, Mona and Morecambe – known as the ‘MoMoMo’ projects – over the impact that wind wakes they will generate could have on its existing assets.

EnBW and BP argue that a study commissioned by The Crown Estate, the seabed landlord for England & Wales, found that at distances much greater than 20km between wind farms, wake losses become “vanishingly small.”

As distance increases, they claim negative effects become “negligible.”

A map of the existing and planned wind farms in the Irish Sea. Orsted's assets are circled in blue and Morgan, Mona and Morecambe are in red.

The developers argue this in support of their position that they should not have to carry out an assessment of the wake losses their new projects could cause nearby wind farms, as Awel y Mor was ordered to do in a groundbreaking decision in 2023.

In January, Orsted submitted a wake loss assessment it said it was “forced” to commission from consultancy Wood Thilsted concerning the potential impact of the projects on its Irish Sea fleet, given BP and EnBW refused to carry out their own.