IN DEPTH: Offshore turbine testing

One of Siemens’ SWT-6.0-120 turbines being installed at Gunfleet Sands 3

One of Siemens’ SWT-6.0-120 turbines being installed at Gunfleet Sands 3

By the end of the decade, the UK hopes to have its national grid humming with 18GW of electricity from wind farms located far from its coastline.

But the new super-sized turbines that are being counted on to make this market-transforming jump in power production aren’t ready for action yet — and time is marching on.

Two years ago, consultancy GL Garrad Hassan ran a “gap analysis” of testing facilities for the next generation of offshore turbines. Though blueprints for a pair of giant 100MW demonstration laboratories off England and Scotland and a small bolt-on site at Dong’s Gunfleet Sands wind farms were already being drawn up, the study flagged up a looming shortfall of grid-connected sites for the host of 6-8MW machines needed for the coming build-out off Britain.

Now it’s sink or swim. If new testing sites are not open for business soon, the hard reality is that several promising turbine prototypes might end up being shelved, potentially causing knock-on delays to the first projects in Round 3 — ultimately a 31GW campaign expected to cost in the region of £100bn ($157bn) — and taking some of the steam out of a supply chain trying to gain momentum.

The Crown Estate, which manages the UK seabed, is about to unveil a portfolio of new demonstration site acreage meant to help solve the approaching crisis.

The Crown Estate’s approach to the new licensing round speaks volumes. Fast-track and holistic, the big idea is to broaden the remit from testing standalone turbines to include trials of next-generation foundations, cabling and even technologies such as jetting ploughs and “smart” trenching devices — in a variety of seabed types.

“The [government’s offshore wind] task force rightly sees demonstration sites as critical to the mix of things that need to happen to get levelised costs down and to do so quickly to make an impact,” says Crown Estate programme manager for technology Adrian Fox.

“The new technology — the bigger, more reliable turbines, for a start — is key, but the question is: where are [these machines] going to be demonstrated?

“For the owners and operators to deploy new turbines, they have to be confident that they are going to work,” continues Fox. “If one turbine goes up and is demonstrated, that’s one turbine to buy; if ten go up, then there is a lot more competition — you see the differences between the technologies and you can begin to make confident technology choices and price choices as well.

”Stakes are high. With the original three demo sites on offer, noted the GL Garrad Hassan report, there would be 20-25 turbine prototypes with nowhere to deploy by 2015, which could translate into five machines’ testing programmes not crossing the commercial finishing line.

The recognition has dawned since that a more holistic testing and demonstration (T&D) tack is needed get wind farms built in the deeper waters of Round 3 projects, while screwing down costs by the government’s target of 30%.

So as well as turbines, foundations are also in the spotlight, with expectations that two of first demo sites — the Blythe Offshore Wind Deployment Site off the National Renewable Energy Centre (Narec) in northeast England and the European Offshore Wind Deployment Centre off eastern Scotland — will see a menagerie of monopiles, jackets and gravity-base structures go in with the first turbines into the water.

Cabling, too, and the high-horsepower devices need to install it, will be integral to the demo site picture, along with support technologies such as offshore access vessels.

Tony Quinn, operations director at Narec, states: “The site... is already pushing the boundaries of existing capabilities and risk tolerance. It... should encourage new alliances in the supply, installation and O&M [operations and maintenance] of the turbines.

”Fox adds: “Everyone needs to contribute [in achieving levelised cost reductions for offshore wind]. You can’t just rely on the turbines, foundations are very important too. Cabling is a small proportion [of overall costs] but improvement in the installation technology will help a great deal on the operational side too.”

Benj Sykes, UK country manager at Dong — which, as part of its Gunfleet Sands 3 project, is the first developer to erect 6MW next-generation prototype turbines off the UK — sees demonstration activities as “a very important part [of its] strategy to maintain and develop competences within development, installation and operation of offshore wind farms”.

“As a part of the demonstration programme at Gunfleet Sands, we will run numerous tests on the two [Siemens SWT-6.0-120] turbines we installed there earlier this year to see what we can learn and take forward,” he says.

“This is an important part of what it takes to make offshore wind competitive with other technologies, and reduce the cost of offshore wind energy in the long term.”The Crown Estate sites that will soon be up for bids have the long-view in mind, with a range of environments, water depths and seabed geologies represented at different locations.“

Simply demonstrating technologies in sand is not the same as demonstrating it in chalk, in soft mud and clay,” notes Fox. “This is true for different foundation types [such as suction caissons, concrete gravity bases and steel jackets] and also for other technologies. You need to demonstrate in a range of seabeds because a developer who has a hard rock site is not going to be interested in a jetting plough that does well in sand.

“There are a range of technologies that need to be tested and demonstrated and there is a range of sites on which this testing and demonstration can take place.”At least two of the sites earmarked for demonstration projects will be tailor-made for floating wind turbines.

One will be off Peterhead, Scotland — where Norway’s Statoil has an “exclusivity agreement” with the Crown Estate for an array of its Hywind spar-buoy machines — and the other is off Hayle, southwest England, at the WaveHub facility, where the Energy Technologies Institute hopes to trial a solo tension-leg platform design topped with a 6MW Alstom Haliade turbine.

Claire Gibson, general manager at Wave Hub, a 20MW wave-power centre by design that is being upgraded to 50MW to accommodate large-scale wind turbine testing, says: “Floating wind platforms could be an answer to addressing the viability gap in deep water and would allow the UK to harness a huge untapped resource.”

The Crown Estate will also be making the case to wind farm operators to open up swathes of their licensed acreage for use in “off-grid” demonstration projects.“There is a mental picture that many in the industry have of a ‘fenced off’ site where you are testing things that are all grid-connected, and what we are saying is that we have to be much more imaginative,” says Fox.“In 2010, it was all about the turbine. Now we see the need for a broader reach — turbines, foundations, cabling, offshore access — so we need a broader definition of what testing and demonstration means.

“What we have to ensure [with these new demonstration sites] is that there is a continual downward path on the levelised cost past 2020. “The wind-power industry has got legs and it is going to be global and you can’t instigate T&D five years before you want to deploy a technology. Demo sites that make it possible to prove up all aspects of the technology are the way forward.”

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