Potential for development in offshore foundations

Wednesday, 29 August, 2012 - 14:45

New concepts for the foundations of offshore wind power systems could improve the energy payback time of the turbines by 100 %. This is the result of a study by Cambridge University.

Jim Platts of the Institute for Manufacturing (IfM) believes that the wind power industry could achieve significantly better payback times if instead of the current steel foundations it used guyed composite towers held in place using steel cables. A preliminary study by the IfM finds that it is possible to halve the amortization time in this way.

For onshore systems the energy balance is around 40:1. At 15:1, that of offshore systems is significantly worse. This is largely due to the offshore foundations, which require up to four times more concrete and steel than foundations onshore, according to the results of the study. "When you look at offshore wind turbines you see a series of slim structures – what you don’t see are the far heavier supporting structures below the surface that they slot into," says Platts. "We urgently need to reduce the high levels of energy embedded in offshore wind turbines, which make them both ineffective in energy payback and costly in financial terms. We can do this fairly easily if we invest in more innovative methods for making and installing the towers and the foundations that support them", he says.

Besides the weight disadvantages, Platts also points out the poor material qualities of steel. In contrast to composites, it is prone to corrosion and fatigue. The question is whether materials other than steel would not be better adapted. "The answer is yes: we can use composites for towers just as we do for blades. They are lighter, stronger, corrosion-free and more resilient than steel." If these lighter towers were anchored with steel cables, even more could be saved on the foundations. The study concludes that an energy balance of 25:1 could be achieved.

Katharina Garus

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ODE, Northland Power and Yushan Energy jointly hosted, at Barrow, a delegation of Civic Leaders and industrialists from Taiwan during their recent offshore wind fact finding mission to the UK. The mission was led by the Chinese International Economic Cooperation Association and was supported by the UK’s Department for International Trade.
The Group, which consisted of representatives from Changhua County and industry leaders from the engineering, finance and power generation communities, met with Northland Power, Yushan Energy, ODE and leaders from Barrow Council to discuss the impact that the Ormonde Offshore Wind Farm had on the Barrow community before visiting the Operations Support Base and travelling offshore to view the wind farm.
ODE was the principle engineering contractor for the Ormonde wind farm and is now closely involved with the development of the Hai Long Offshore Wind Farm in the waters off Changhua County, Taiwan, for developers Northland Power and Yushan Energy.
The Taiwanese visitors had a chance to learn about the construction of the offshore wind farm, its support base and how the operation and maintenance aspects of the wind farm have benefited the local economy during and following the construction period.
The Hai Long development is many times larger than the Ormonde development but many of the challenges and opportunities are the same. Like Ormonde, Hai Long will be using jacket technology for foundations and where Ormonde was the first wind farm to use 5mw turbines, Hai Long will also be using industry-leading turbine technology.
The delegation found other similarities in the projects with regard to the investment in port facilities, today Barrow’s Ramsden Dock is the centre for operations and maintenance support for four offshore wind farms but a tidal range of over ten metres and harbour walls dating from the late 1800’s posed challenges during construction. The solution of a floating pontoon that does not transfer load to the aged sea walls is one that may find an application in the ports and harbours of Changhua County.
Peter Godfrey, ODE Managing Director, said “It’s been tremendously useful to revisit Ormonde and showcase the engineering required both on and offshore to make an offshore wind farm a success for the developer and local community. Barrow council, Vattenfall, the current operator of Ormonde and of course the DIT have been very helpful in making it possible to share the lessons learned from this development”.
Ian Hatton, who previously was with Eclipse Energy, the developer of Ormonde, and is now CEO of Yushan Energy, agreed “The Hai Long project that we are undertaking with Northland Power in the Taiwan Straits is a multi-billion pound investment into the renewable infrastructure of Taiwan. It’s easy to get caught up in detail of building the project, but it’s not until you return to a project such as Ormonde that you see the benefits brought to the local community in terms of ongoing investment and jobs. I hope this is what the delegation takes away from their visit to Barrow”.
Sean McDermott, General Manager, Northland Power Development Co. Ltd., Taiwan, added “We were very excited to work with Yushan Energy and ODE to host the delegation from Taiwan to visit Barrow and learn about the scale and positive impact offshore wind development can have on industry and communities. Taiwan has some of the best offshore wind resources in the world, and these sort of visits and exchanges help Taiwan prepare to fully harness this potential. With our partners, we look forward to continuing to contribute to that process”.