It’s a familiar dilemma: you’ve bagged yourself a home with uninterrupted views and then someone else comes along and spoils it. Or maybe a tree in the garden next door has grown so tall it is blocking out your sunlight.
How can you amicably resolve this dispute with your neighbour?
Yet in this case it’s not the views that are being ruined, but the wind – and the stakes are significantly higher.
Through a phenomenon quaintly described as the “wake effect” by academics, Britain’s biggest wind farm owners fear the wind is literally being taken out of their sails.
It is a problem that threatens to cost the likes of Ørsted, RWE, Scottish Power, Total and Equinor billions of pounds without resolution, with the companies waging war in the planning system over who will take precedence – and who picks up the bill.
Flustered industry insiders have even coined a term for it: wind theft.
In recent months, the issue has caught the attention of ministers amid concern that it risks creating unhelpful turbulence for Ed Miliband, the Energy Secretary, as he seeks to steer the country towards a clean power system by 2030.
Wind wars
Wind theft occurs when air hits the turbines of one wind farm, leaving behind less powerful air flows for those positioned downstream - Ørsted
To ensure wind theft doesn’t blow him off course, Miliband recently commissioned a national study led by Manchester University that will establish a proven method for calculating the wake effect, how it impacts revenues and how to prevent or resolve neighbourly disputes.
The goal is to avoid the sort of scenes unfolding off the coast of Europe, where Belgium is being blamed for stealing wind from the Dutch, and the Dutch are themselves accused of sapping gusts claimed by Germany.
“The main problem for the wind industry is that there is currently a lot of uncertainty,” says Pablo Ouro, a renewable energy expert who is leading the Manchester University study. “And uncertainty is not good news for financial projects.”
Wind theft happens when air hits the turbines of one wind farm and is disrupted, leaving behind less powerful air flows for wind farms positioned further downstream.
It had not been much of a problem for the offshore wind industry until relatively recently. But there is only so much seabed that is suitable for fixed wind turbines, and the turbines themselves are growing in size.
As recently as the mid-2010s, a typical turbine was just shy of 200 metres tall. Now, monsters like the world’s largest turbine being built in Bradenberg, Germany, can reach as high as 364 metres – higher than London’s Shard skyscraper.
2405 Wind Turbine
And as the turbines grow bigger, so do their wakes. This means that for upcoming projects, the wake effect of one wind farm can easily still hit another as far as 37 miles (60km) away, says Ouro.
The extent to which this saps the output of the affected wind farm might be relatively small. Yet when this is compounded over many years, the financial consequences can be disastrous for developers.
“The differences from the wake effect are not huge, in the sense that there will not be an impact of more than say 4pc to 5pc,” Ouro says. “But actually, for a relatively large wind farm over more than one year, that’s a lot of money.
“So even if it’s a small chunk, it has a quite large impact on the losses.”
Earlier this year, for example, Ørsted and Equinor complained that Total’s proposed Outer Dowsing wind farm off the Yorkshire coast could cost them a combined £363m in lost revenues.
Ørsted estimated that the scheme would affect its existing Race Bank, Hornsea 1 and Hornsea 2 projects, sapping 0.52pc, 0.67pc and 0.68pc of their outputs respectively at a total cost of up to £199m.
Meanwhile, Equinor says its Dudgeon and Sheringham Shoal projects will lose 0.88pc and 0.76pc respectively, with planned extensions also set to suffer. The company predicts the cumulative impacts could amount to up to £164m in lost revenues.
2405 Wind wars: the fight over the North Sea breeze
Elsewhere, Scottish Power owner Iberdrola alleges that RWE’s proposed Five Estuaries project will reduce the output of its East Anglia 2 wind farm by as much as 2.1pc.
That has prompted RWE to hit back and accuse its rival of hypocrisy: East Anglia 2 is sapping the wind of its Galloper or Greater Gabbard wind farms, it says.
And yet another row is raging in the Irish Sea, where Ørsted is duking it out with EnBW, BP and Flotation Energy over the effects upcoming projects could have on its existing portfolio.
Headache for Miliband
All told, around 20 gigawatts (GW) of wind projects are now ensnared in wind theft disputes, according to the consultancy Tamarindo.
Kester Gunn, the renewables chief scientist for RWE, which is a partner in the national wake effect study, has warned that settling such disputes is tricky business.
Calculating precise numbers for impacts is made harder by the constantly changing wind direction, although the prevailing wind in the UK is generally from the south-west.
“Full wake mitigation between wind farms is not possible, but wind farms are designed so that the wake effects between the turbines are reduced as much as possible,” Gunn said in a recently published article.
“When we assess wake losses we have to take the average effect over all weather conditions. Even very large wake effects for one wind direction tend to average out to very small impacts – less than 1pc – over the year.”
Equinor, a leading partner in the giant Dogger Bank wind farm development in the North Sea, said wake effects were a serious threat to future developments.
“These effects are too often underestimated,” a spokesman says.
The tension building over wake conflicts is so great that it could undermine Miliband’s plans to turbocharge offshore wind capacity.
The UK has about 2,800 offshore wind turbines with about 15GW of generation capacity today. Miliband wants to more than triple this to 50GW by 2030, with even more planned after that.
2601 Britain is switching to a renewables-heavy grid
Overall there is about 77GW of capacity in the planning pipeline, roughly equating to 8,000 turbines to be added to the 2,800 already in place.
As development gathers pace, so is pressure for a more systematic approach to wind theft.
Until now, such conundrums have been dealt with by the Planning Inspectorate on an ad-hoc basis.
But Miliband’s decision to commission the Manchester study underlines a view in Whitehall that a proper framework is now needed to deal with disputes.
The Government says the Crown Estate, which is responsible for leasing seabed to wind farm developers, already takes some measures to reduce wake effects, such as ensuring there are “buffer zones” between wind farms.
But a spokesman adds that officials soon hope to develop “clearer guidance to manage wind wakes” following the Manchester study.
“It’s likely that any solution or mitigation will mean changes to the way these buffer zones are designed,” the spokesman says.
Further down the line, some industry insiders are also lobbying for a compensation regime to be agreed for wind farms that lose out from the wake effect.
“The main disagreement is actually, do we have models that capture the dynamics of these inter-wind farm wake effects?”, says Manchester’s Ouro.
“That’s what this project is trying to do. And we’re working with the industry to improve the confidence in these models, because, in the end, we all know that wake effects are not going away.”
