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Deep solutions

When it comes to realising the opportunities offered by the growth in offshore wind farms, the concrete sector is “under starter’s orders”. NCE reports.

BAM_Wind_Energy_in_paretnership_with_Van_Oord_projects_bv

Positive outlook: The UK’s massive offshore market is boosting opportunities for the concrete sector

Late last year advocates of concrete gravity bases as foundations for deep water offshore wind farms gathered to hear what hope lies ahead for their technology. The outlook is very positive.

“The prognosis for steel bases is low,” Crown Estates development manager for offshore wind test & demonstration Ian Bryan told delegates at December’s Concrete Offshore Wind 2012 conference and exhibition.

“The supply chain cannot match demand. Whereas the concrete sector is making a very real case for concrete foundation solutions that is increasingly being taken on board by the renewables industry,” he said.

“The concrete sector is making a very real case for concrete foundation solutions”

Ian Bryan, Crown Estates

Bryan has a clear vested interest in ensuring the right technology is rolled out. He will be leading on both the delivery of current demonstration sites and development of new initiatives to allow emerging technologies to be demonstrated at scale as part of the drive to reduce the lifetime cost of energy for offshore developers.

So his endorsement of concrete over steel is significant. According to conference organiser the Concrete Centre, his view is a recognition of the progress and development of industry gravity foundation construction and installation solutions that, combined with the growing recognition of concrete performance and environmental benefits, means that the concrete sector is ready to realise the opportunities presented by the Crown Estates Round 3 leasing programme.

Opening the conference, John Bingham, Royal HaskoningDHV offshore managing agent for the Crown Estate and chairman for the Concrete Centre’s interest group for gravity foundations - offshore wind, highlighted how the scene is now set for concrete gravity foundations to help deliver the full potential of offshore wind renewable energy.

Significant progress has been made on the development of a wide range of foundation solutions that are cost effective, require minimum maintenance and offer long term performance, he said. Increasingly, he added, these solutions are being recognised as offering the best environmental choice. As a result, the renewable energy industry is taking the option of concrete gravity foundations far more seriously.

The UK is already the world’s largest offshore wind market and, as Bryan explained, that lead will be cemented by the potential of 32GW generated from Round 3 offshore wind farms in addition to the 8GW of energy from previous rounds.

Seatower

Underwater: Gravity bases sit on the seabed without the need for piles

There is steady progress being made on gaining planning consents, on the development and delivery of regulatory frameworks and on reducing the cost of offshore energy to £100/ MWh by 2020, which will make the cost of offshore wind energy comparable with other low carbon technologies. All this is good news for the concrete sector as was further underlined by Bryan’s endorsement of concrete bases.

The need for the potential of Round 3 to be realised is underlined by the fact that currently renewables supply 10% of UK electricity. By 2020 the target is 35%. “The main driver for growth in renewables will be wind,” said Renewable UK offshore renewables director Nick Medic at the conference. “You cannot have a low carbon energy supply without it.” The wind farms proposed under the Round 3 leasing programme will deliver 30% of the UK’s electricity supply from up to 6,000 wind turbines. “That is a considerable growth market for concrete gravity foundations,” said Medic.

The potential for renewables to provide the UK with energy security was highlighted by Department of Energy and Climate Change head of wind business development David Curran. He called for a major programme of investment in a mix of nuclear and renewable energy and believed that the newly agreed low carbon subsidy system would provide the assurance of necessary funding for renewable energy development by providing stabilised income streams.

This is important if developers are to be attracted to invest in renewables. Making such investment more attractive will support the development of off shore wind farm projects.

It is important that the UK benefits from providing the framework for an attractive investment environment. One of the best ways of ensuring this is to ensure a high UK content in off shore wind farms in terms of material supply and workforce. This, explained BVG Associates associate Chris Willow, has an important political message: “Having a real measured UK content in off shore wind farms demonstrates ‘payback’ for subsidies and links their development to UK jobs and investment,” he said. “Concrete gravity foundations by being UK sourced can help meet the objective of a UK input and content of up to 60% for off shore wind farms.”

Gravitas

Ready for launch: bases are built on land and towed out to sea

Against this background, the concrete sector has developed a new generation of gravity bases that offer particular advantages for offshore locations. Concrete gravity bases, typically in the form of cellular caissons ballasted with gravel or sand, are low maintenance, have considerable design flexibility and whole life cost efficiencies.

In particular, the high damping properties of concrete minimises vibration. This negates potential structural fatigue. Onshore construction of the concrete bases provides certainty of programme as potential weather delays are minimised, while the development of innovative placement techniques eases the installation process and minimises the use of expensive heavy lifting equipment.

“Ongoing technological construction and installation developments for concrete gravity bases will add to their advantages by helping to deliver construction, installation and operation cost reductions for off shore wind farms”, explained Concrete Center consultant Alan Bromage.

The avoidance of piling during installation is a major environmental benefit of concrete gravity bases over other foundation types that require driving steel piles into the sea bed.

“No piling is required for gravity concrete bases. They are lowered into position,” explained Marine Space principal marine ecologist Ian Reach. “The avoidance of piling is an environmental advantage for concrete gravity bases as the impact on marine life from piling noise is likely to lead to planning conditions being applied resulting in project delays and increased costs.

“No piling is required for gravity concrete bases. They are lowered into position”

Ian Reach, Marine Space

“With this in mind, retaining concrete gravity bases as an option through the planning process is a prudent priority for developers.”

Monopiles, steel jackets, tripods and floating platforms all require drilling or hammer piling to secure then to the seabed. The noise and vibration impact of this will increase due to the increased size of the foundations necessary for Round 3 deep water locations.

The attractiveness for developers of removing the environmental issue of piling noise was underlined by Royal Haskoning DHV project manager Adam Pharoah, who stated: “Developers would be bound to prefer nonpiled foundations it they were technically proven and cost effective. If this critical point is reached in the development of low noise foundations, people may then start ruling out piling to reduce their consenting risk”.

Bromage added: “Encouraged by the coming together of product and supply chain development, the provision of planning consent frameworks and stabilised investment environment plus the growing recognition of the benefits of concrete gravity foundations for off shore locations, particularly for the deep waters of Round 3, the concrete sector is ready to play its part in ensuring that the UK has a secure and sustainable energy supply.”

Readers' comments (1)

  • Are we not missing a trick in the construction of offshore wind farms? These structures involve the construction of hollow caissons which could be constructed to include wave powered turbines within them to produce electricity. Although wave energy turbines may not be efficient on their own, as the infrastructure is already be provided, there there is only the marginal additional cost for the turbines. Surely any technology that even marginally increases the overall efficiency these wind farms should be considered?

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