New Scientist
Offshore wind farms in Europe are causing problems as new turbines block wind from older ones. This “wake effect” can cut power by up to 30 percent. The UK is now studying how to reduce these losses to protect clean energy goals and future projects.
Wind farm developers are worried about neighbours stealing their wind
Author: Madeleine Cuff
IMAGINE you have just built yourself a lovely new house with an unobstructed view of some nearby mountains. But, within months, someone else starts building a home right in front of yours, blocking your view. A neighbourhood dispute looks inevitable.
A similar scenario is playing out across northern Europe with the rapid development of offshore wind farms. As the seabed becomes increasingly crowded with turbines, developers are becoming concerned that new wind farms could “steal” wind from existing sites.
The problem lies with wind farm wakes. “The job of a turbine is to rotate a set of blades that extract energy from the incoming wind. But, as you extract that energy, then you leave behind much lower energy,” says Pablo Ouro at the University of Manchester, UK. That creates a region of “low-velocity wind”, he says, which can extend for tens of kilometres.
The issue has become critical as more offshore wind farms have sprung up and turbines have become larger and more powerful, creating bigger wakes. At least a dozen disputes have broken out among clean-energy developers in the UK as they jostle to protect their wind resources from neighbouring projects, according to Sarim Sheikh, who previously led General Electric’s offshore wind business.
“Wake effects are nothing new. It’s been there since the very beginning of wind farm development,” says Sheikh. “What has changed over the last few years has been the rapid scale of the growth in the size of wind turbines.”
Estimates of the financial impact of wake losses vary. Research published last year by a team at the University of Bergen in Norway suggests wind farm wakes can extend up to 50 kilometres and cut wind resources available to downstream farms by as much as 20 per cent. Other estimates from researchers in the US suggest wakes could affect yields by more than 30 per cent in certain severe conditions.
Most in the wind industry work on the assumption that wakes can cut the yield of nearby wind farms by well below 10 per cent. “The big numbers are, in the main, taking an extreme, specific scenario,” says Joel Manning at UK consultancy K2 Management, which conducts energy-yield analysis for wind developers.
30%
How much wake effects could cut wind farm yields, in severe cases
But even yield losses of a few per cent can have a huge impact on an industry working within increasingly tight margins. “This is something that is a worry, especially from an investment point of view and profitability of existing or future projects,” says Ouro. Ultimately, financial uncertainty and reduced profitability could result in increased power prices and reduced capacity.
In the UK, the government wants to dramatically increase offshore wind power to make it the backbone of the country’s future clean power grid. It has set a target to increase capacity from the 15 gigawatts currently in operation today to 43 to 50 gigawatts by the end of the decade.
Accurately assessing the impact of wake effects is therefore crucial for the UK’s climate goals, says Ouro. “Net zero is not about how much capacity, how many gigawatts we install. It is how many gigawatt hours [of electricity] we can produce.”
Last month, the University of Manchester launched a national assessment to try to quantify the problem for UK developments. Ouro is leading the 12-month project, which will work with offshore wind developers to model how wind farms set to be operational in 2030 will affect the yields of those currently generating electricity. It will be the first assessment of its kind in UK waters.
Test the waters
“The biggest outcome is that we can inform the future lease sites… so we can reduce the wake effects,” says Ouro. That might mean tweaking the boundaries of wind farm sites to include larger “buffer zones” between neighbouring farms, for example, or changing the orientation of sites to reduce the wake effect. “If we were to provide information on where to put future turbines, if we improved that a bit, that would be a huge success, because that is a benefit for taxpayers and everyone,” says Ouro.
But planners must strike a balance between maximising power output from UK waters and ensuring the country remains attractive to offshore developers. Other nations are watching the UK’s response closely. “This is not just a North Sea issue. This is very much an international issue,” says Eirik Finserås at Norwegian law firm Wikborg Rein.
In the meantime, firms with sites already in development or under construction are battling it out in the planning and legal systems to protect their wind resources. Some are establishing “wind wake agreements” that might include compensation for affected wind farms, as well as agreements to design new sites to minimise downstream impacts.
Yet despite the concern over wind wakes, the UK remains a world-leading market for offshore wind developers, with favourable government policies and generous pricing contracts. For many, that is worth risking some trouble with the neighbours.
Credits: TCA, LLC.