‘Wind theft’: The mysterious effect plaguing wind farms

This is about the well-known ‘wake effect’, described here as ‘a phenomenon of great relevance in the field of wind energy’. A recent Recharge News report said: ‘Equinor and SSE say that wake losses caused by an RWE offshore wind project will cost their massive Dogger Bank arrays £582m ($778m) over their lifetime, arguing it would be “perverse” not to require mitigation or compensation as a result.’ So offshore wind is not as simple as picking a site and plonking down some turbines, if competitors might see legal issues arising with large sums of money at stake. Another issue, not mentioned below, is that wind turbines in some offshore areas are playing havoc with the UK’s air defence radar, likely costing £1.5 billion to overcome or mitigate, as the Daily Sceptic reported.
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As offshore wind farms are expanding around the world in the race to meet net zero climate targets, a worrying phenomenon is attracting growing attention: in some conditions, wind farms can “steal” each other’s wind, says BBC Earth.

“Wind farms produce energy, and that energy is extracted from the air. And the extraction of energy from the air comes with a reduction of the wind speed,” says Peter Baas, a research scientist at Whiffle, a Dutch company specialising in renewable energy and weather forecasting.

The wind is slower behind each turbine within the wind farm than in front of it, and also behind the wind farm as a whole, compared with in front of it, he explains. “This is called the wake effect.”

Simply put, as the spinning turbines of a wind farm take energy from the wind, they create a wake and slow the wind beyond the wind farm.

This wake can stretch more than 100km (62 miles) for very large, dense offshore wind farms, under certain weather conditions. (Though more typically, the wakes extend for tens of kilometres, according to researchers). If the wind farm is built upwind of another wind farm, it can reduce the downwind producer’s energy output by as much as 10% or more, studies suggest.

Colloquially, the phenomenon is known as wind theft – though as Eirik Finserås, a Norwegian lawyer specialising in offshore wind energy, notes: “The term wind theft is a bit misleading because you can’t steal something that can’t be owned – and nobody owns the wind.”
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While the problem of wind theft has been long known in principle, it is growing more pressing due to the scale and speed of the offshore expansion, and the size and density of offshore wind farms, experts say.
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Currently, there are a number of disputes in the UK between offshore wind farm developers over potential wake effects.

Full article here.