A monopile wind turbine

Offshore windfarms stretch manufacturing supply chains

As the offshore wind energy market expands, can its supply chains take the strain? As the offshore wind energy market expands, can its supply chains take the strain? Manufacturers of turbine foundations are eyeing the sea of opportunity that is surfacing, but many in the industry are concerned suppliers won’t meet the uncertain demands of a new and rapidly evolving sector.

With offshore wind energy in the UK poised for rapid growth, manufacturers of turbine foundations are eyeing the sea of opportunity that is steadily surfacing. Parallels have been drawn between this industry’s growth and the energy boom of the 1960s and 1970s, but already many in the industry are concerned suppliers won’t meet the uncertain demands of a new and rapidly evolving sector. The proposed scale of offshore wind energy development is breathtaking. According to the European Wind Energy Association (EWEA) a hefty 1,567MW of new capacity was added to the grid in European waters in 2013, some 34 per cent more than in 2012. What’s more, 12 offshore projects are currently under construction, and these are due to add a mighty 3GW to the region’s grid.

As these projects gather pace and leave the coastlines for deeper waters, manufacturers of substructures for the oil and gas industry are now looking to supply the foundations for offshore wind turbines. Denmark-based steel contractor Bladt, UK oil and gas structure manufacturer TAG Energy Solutions, and German heavy-plate producer Dillinger, are among some 15 firms already providing substructures for offshore wind energy projects. But turbine foundations pose a problem.

Today, the so-called monopile is the foundation of choice. Accounting for 76 per cent of all European offshore wind installations to date, this single steel pile, hydraulically driven into the seabed, is simple and will continue to be used wherever possible. But herein lies the challenge.

As the offshore wind industry develops, progressively larger turbines will be deployed further out to sea to harness the wind’s potential in these deeper waters. And so the monopile will flounder. While cost effective in relatively shallow waters, this foundation design is limited to water depths of around 30m, and struggles to support turbines greater than 3MW in size.

As Athanasia Arapogianni, senior research officer from industry association EWEA, says: “The main drivers behind substructure choice are seabed conditions, sea conditions and turbine size. So far most projects have been developed in relatively shallow waters and so monopiles have been the best solution.”

Indeed, EWEA figures indicate the average depth of water of wind farms completed or partially completed in Europe in 2013 was only 20m, with the average distance to shore some 30km. Meanwhile, the average size of offshore wind turbines installed in 2013 was 4MW; with Siemens’ 3.6MW turbines being developers’ dominant design choice.

Wind project foundations

This this will soon change, however. Construction of the UK’s third round of offshore wind energy projects is scheduled to start this year, and many of these wind farms will be built in water depths of at least 25m and in some cases up to 60m.

Monopile foundation suppliers have built bigger and stronger structures. Diameters have been stretched from 4.5m to 7m, with some firms now working towards 10m. But, without a doubt, this is pushing the limits of monopile design. So where next? The answer, for now, lies in the oil and gas industry.

A jacket-type foundation comprises a steel frame design extending from the mudline to above the water, and depending on exact design, can be used in depths up to 50m, some sources cite 70m.

Widely used in the oil and gas sector, these foundations have also been used in a handful of wind projects. These include the UK’s Ormonde offshore wind farm positioned up to 21m deep in the Irish Sea, the Beatrice Wind Farm Demonstrator Project sitting 45m deep in the Moray Firth, North Sea, and Thornton Bank, off the Belgian coast in waters up to 27m deep.

Given this experience the jacket foundation is the favourite to take turbines to greater water depths, but the journey out to sea is not simple. Jacket substructures come in a range of flavours - from six-legged designs to ‘twisted’ versions’ - and the choice doesn’t stop there.

Designs for various depths

At the same time, other fixed foundation designs are stepping up to the challenge. Tripod designs are three-legged steel space frame structures with a central steel shaft attached to the turbine tower. These are suited to water depths of 30 to 50m and have already been used in Germany’s first offshore wind farm, Alpha Ventus, in North Sea waters some 30m deep.

Meanwhile tripile foundations consist of three foundation piles connected via a transition piece to the turbine tower. These have been used to support 5MW turbines in 40m water depths at the Bard Offshore 1 wind farm in the North Sea off the coast of Germany, accounting for 5 per cent of new installations in 2012.

Moving away from three-legged structures, gravity foundations are large-diameter concrete and steel structures that rely on weight to resist wind and wave loading. These are generally suited to water depths of up to 30m, account for around 16 per cent of all European offshore installation, and haven’t yet been used in the UK. Additional designs include braced monopiles as well as monopods that use suction buckets to provide the seabed connection.

Myriad deeper water foundation designs twinned with rapid industry growth doesn’t make life easy for substructure suppliers trying to anticipate industry demand; can these manufacturers really be expected to forecast the industry’s needs? Continental European players are making progress.

Germany-based RWE Innogy has installed 49 jacket foundations, to support 6MW turbines and a substation in water depths up to 25m, at its Nordsee Ost offshore wind farm, 35km to the north-east of the island of Helgoland, in the North Sea. These foundations were manufactured by Kvaerner in Verdal, Norway.

At the same time, the 400MW Global Tech 1 project in the North Sea is using tripod foundations for its 5MW wind turbines sitting in water depths of 39-41m. These are being constructed by several companies including the Arge Tripod Global Tech 1 consortium, comprising Germany-based foundation manufacturers WeserWind and Erndtebrücker as well as Eisenwerk and Siag.

Laying UK foundations

UK manufacturers, however, are facing a tougher time. To date, companies from continental Europe have supplied the lion’s share of foundation structures for the offshore wind sector and, as a result, have a relatively established supply chain.

But over in the UK the situation is very different. For example, one established monopile production facility exists in Haverton Hill Yard, Billingham, owned by TAG Energy Solutions, while BiFab operates a steel jacket foundation production facility at Methill, Scotland.

Given these and a few other limited manufacturing facilities, industry players have been calling for UK investment to upscale production and establish a strong supply chain for the manufacture of foundations. As former chief executive of TAG Energy Solutions, Alex Dawson, says: “We need to have significant investment if UK companies are to have a share of Round 3 projects.”

What’s more, Dawson highlights how the UK’s second tier supply chain - suppliers of walkways, hand rails and other subcontracted elements - also needs to be upscaled. “There is an existing subcontractor base in the oil and gas sector but it needs to upscale to develop a serialised production base, rather than produce on a one-off project basis.”

Promising developments for the overall supply chain in the UK are emerging. In December 2013 UK government granted planning permission for the development of a £450m industrial base for the offshore wind sector - the Able Marine Energy Park - spanning some 900 acres on the east coast of England. The Able UK-owned Park will house suppliers of components for offshore wind turbines and provide an assembly and installation base for North Sea projects.

In March this year, manufacturing heavyweight, Siemens, unveiled plans to invest £160m in offshore wind production in the region. At the time of writing, the Able Marine Energy Park was facing delays while Parliament investigated a dispute over land with Associated British Ports, but both developments signal healthy UK supply chain developments.

At the same time, suppliers of foundations are also exploring ways to minimise risk and reduce costs. Maximising onshore assembly of wind turbines would enable more streamlined, serial production, which is something that UK-based TAG is looking to achieve across its supply chain.

The UK manufacturer is also looking to standardise as many parts as possible and adopt rapid assembly techniques. Such measures would create more efficient supply chains for both the monopile and steel jacket markets, and could even lead to a certain level of convergence between the two.

Convergence or not, EWEA’s Arapogianni, like many more in the industry, doesn’t believe that uncertainties in future foundation choice should pose a risk to future investment. As she points out, jacket designs, for one, have a ‘track record’ with all indications pointing to these structures being the future foundation of choice. Other challenges are also being tackled.

“[Industry] need to make sure there is enough steel at a good price,” she says. “In addition, size is an issue; these structures are very large and need large areas next to the coast for construction.

“But this, in turn, will drive the vessel industry,” she adds. “It’s like a chain reaction - everything needs to adapt.” *

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