Type Failure or Wear and Tear in European Offshore Wind?

Recent reports indicate that major repairs are required on 500 offshore wind turbines in United Kingdom waters, and nearly two hundred more at sites off the Danish and German coasts. Whether this is type failure or just normal wear and tear is as yet unclear, and is, according to Danish news reports, in dispute.

One of the principal disadvantages of rapid and inorganic technological deployment, such as that required by the European Union’s renewable energy targets, is that problems are very widespread by the time they are discovered. The prudent approach is to stay behind the learning curve, so that the consequences of type failure affect only a small number of installations. Dashing ahead of the learning curve is asking for big trouble.

Recent weeks have seen several reports that Ørsted, as DONG Energy is now called, is faced with the distressed repair of over six hundred offshore wind turbines supplied by Siemens. Five hundred of these are in British waters, and somewhat over one hundred are offshore Denmark, with a further 80 in German waters.

West of Duddon Sands, a joint venture between Ørsted and ScottishPower, is an offshore wind farm of 108 Siemens 3.6 MW turbines (SWT 3.6 MW) with a total capacity of 388.8 MW. It was officially opened by the then Secretary of State for Energy and Climate Change, Ed Davy, and began generating in February 2014.

It now appears that all 108 wind turbines have erosion problems on the leading edges of their blades, requiring removal and reconditioning. Renewable Energy News (renews, issue 377, available only to subscribers), is reporting that this will entail the application of a rubber covering, a process that will take three to ten days per turbine. Work is expected to start later this year and will stretch into 2019.

Renewable Energy News added that this problem was also present at Ørsted’s Walney 2 offshore windfarm, a site comprising 51 Siemens 3.6 MW turbines with a capacity of 183.6 MW.

In total, Renewable Energy News stated that the problem was found in 500 UK offshore wind turbines, and was probably also found in at least one, unnamed, German offshore wind farm, affecting some 80 turbines.

The Danish newspaper Jyllands Posten (Danish report here: and translated here) and RE News online are now both reporting that the problem also affects the Danish Anholt offshore wind farm, a site comprising 111 Siemens 3.6 MW turbines,with a total capacity of 400 MW. Some 27 of the wind turbines were repaired last year, 2017, and the remaining 84 are scheduled for repair in the coming year.

The Siemens 3.6 MW turbine which appears in all these instances entered the market in 2010, and there are, according to RE News, some 950 in European waters.

The cost of the repairs will almost certainly be very large. Assuming a repair vessel charter rate of about £150,000 per day, and, say, five days per turbine, this amounts £750,000 per turbine, plus additional labour and equipment costs. In total the cost seems unlikely to be less than £1m per turbine, which equivalent to between 5% and 10% of the total project cost. Even if it is only half that sum, this is a very expensive repair very soon after commissioning, to say nothing of the lost generation and income during the repairs.

It is not yet clear who is to pay for this work. The Jyllands Posten noted that Siemens was thought to have granted five year warranties, with the implication that many of the affected machines would still be covered, and they observed that the Danish subsidiary of Siemens Gamesa “has just provided 4.5 billion Danish Krone ($750 million) or 16% of its revenue to guarantee its commitments.” However, they added, there was “disagreement between Ørsted and Siemens Gamesa as to whether the problems are covered by the guarantee or are a case of ordinary wear and tear.”

There is a lot more at stake here than the allocation of a painful repair bill. If this is a type failure affecting the SWT 3.6 MW device only, then it is a very expensively learned lesson, bad news for Siemens, perhaps hitherto regarded as the premier manufacturer of wind turbines, and unlikely to be forgiven by investors, but of only indirect significance for the wider industry.

But if the need for these repairs is, as Siemens is apparently contending, just every day wear and tear, then this sort of problem is unlikely to be confined to the SWT 3.6 MW device, and will be strong evidence confirming long-held suspicions that developers and owners have greatly underestimated the normal cost of wind farm Operation and Maintenance (O&M).