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Ofshore wind energy: Weighty challenge

Engineers are hard at work to ensure UK produced concrete gravity bases are central to the Round 3 offshore wind programme. Declan Lynch and Daniel Fulcher find out the latest developments.

The much trumpeted Crown Estates’ £75bn Round 3 offshore wind programme is slowly moving from the drawing board to the seas surrounding the British Isles.

The programme to construct 10,000 wind turbines around the UK by 2020 - each up to 200km offshore and in water up to 60m deep - is clearly challenging.

But the government, Crown Estates and energy firms are committed to making it happen, driven by the energy market reform currently under consultation and strict European Union renewable energy targets.


But there are concerns that UK contractors will not benefit from this programme. Recent offshore wind projects, such as the Thanet wind farm off the coast of Kent, have seen less than 10% of the workload going to UK contractors and suppliers.

The lack of UK involvement is primarily down to the fact that the majority of turbine manufacturing facilities are based abroad and are placed on imported steel monopiles.

But industry body The Concrete Centre is keen to change this. Its head of civil engineering Alan Bromage believes that in the deeper water depths of over 20m that will be common in Round 3 zones, concrete gravity bases can become an economic and environmental alternative to steel monopiles.

“We need to persuade developers that concrete gravity bases, which use local labour and material, are economically viable,” says Bromage.

“We need to persuade developers that concrete gravity bases, which use local labour and material, are economically viable”

Alan Bromage, Concrete Centre

The Department of Energy and Climate Change (Decc) has set a target that at least 50% of the work in Round 3 zones goes to UK firms. Bromage says that if zone developers specify concrete gravity base foundations with UK sourced aggregates, cement and reinforcement then the 50% target is well within reach.

But Bromage is aware there are plenty of challenges. “Developers are reluctant to try anything different,” he says.

Since Crown Estates signed the developmental lease for the zones in 2010, gravity base developers have been trying to pitch for work. But with construction on Round Three sites due to begin in 2015, now is the time for action.

Of all the firms developing concrete gravity base solutions, German contractor Strabag is furthest progressed.

The firm has already received an order for 850 gravity base foundations for a German offshore wind zone and has begun construction of a 55ha production plant in Cuxhaven, northern Germany.

Special interest group

Although the firm has not received any UK-based order yet Strabag engineer Robert Foyle believes The Concrete Centre’s offshore wind special interest group has garnered interest in the technology.

“Two years ago steel was the favourite for use in [offshore wind] developments,” says Foyle. “By working with The Concrete Centre there is serious interest and involvement with concrete foundations being developed and implemented.”

The most advanced UK-based venture is the Gravity Base Foundations (GBF) consortium consisting of contractor Vinci Construction UK, its French sister company Freyssinet, Danish consultant Ramboll and marine specialist BMT Nigel Gee.

GBF is part funded by government-backed environmental advisory firm the Carbon Trust and is due to begin demonstration testing of its base in 2013, with commercial roll-out in 2014. However, GBF is yet to receive any orders for the units, and is unlikely to build a production site to build a full scale base until it has done so.
Consultant Arup has teamed up with contractors Costain and Hochtief to form the Gravitas consortium. Gravitas has finalised a preliminary design for its concrete gravity base foundation but has yet to build a prototype.

The firm is holding out on constructing a prototype until it receives an order, and it would be another 12 months from then until the prototype is ready. Gravitas is hoping to pre-qualify for the Hornsea Round Three offshore wind zone, but Arup director Gordon Jackson is concerned the UK is not ready to reap the rewards offered by the construction programme.

“Currently the 50% target is unrealistic without considerable changes and action being taken,” says Jackson. He added that the UK’s free market policy is undermining the country’s attempt to use more local-based content.

Developers will soon begin to choose their preferred foundation type as they prepare to submit planning applications to the Infrastructure Planning Commission’s successor from the end of this year.

As of yet, none of the nine developers active in UK waters have chosen a concrete gravity base solution. The UK construction industry must hope that changes.

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