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LORC tests and demonstrates technology for harvesting renewable energy offshore

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Meeting industry’s needs for environmental testing of large components for offshore use is now one step closer with the ordering of a climatic chamber for a new LORC test centre.

Read more about the environmental testing of structures here

 

 

 

Always on the lookout for improvements

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onsdag 20. april 2011

FACT BOX

Vessels and people working with foundations on Walney 2

• Installation vessel, Svanen (45 people)
• Installation vessel, Goliath (40 people)
• Several tugs 4-5 (15 people)
• Scour protection vessel, Pompei and Rollingstones (40 people)
• Diver vessels, Performer and Supporter (10 people)
• Crew vessels 2-3 (5 people)
• Onshore (15 people)

Learn more about the Walney project at www.wowind.co.uk

About Walney Windfarm

The Walney Offshore Windfarm project is located approximately 15 km west of Barrow-in-Furness in Cumbria and covers an area of approximately 73km2. The project consists of Walney 1 and Walney 2, each with 51 turbines of 3.6 MW, giving a total capacity of 367.2 MW which makes this wind farm one of the largest in the world. Construction of Walney started in 2010 and will be completed by 2012.

Price: Excluding the connection to the British electricity grid, the CAPEX (Capital Expenditure) of Walney 1 and 2 is expected to be approximately £1 billion.

• Water depth: Walney 1: 20-24 meters. Walney 2: 25-30 meters.
• Monopile: Walney 1: up to 55 meters tall and weighs up to 552 tonnes. Walney 2: up to 69 meters long and weighs 810 tonnes.
• Transition piece: Each piece weighs 290 tonnes and is 25 meters tall.
• Foundation penetration into seabed: Walney 1: up to 27 meters. Walney 2: up to 34 meters.
• Total estimated capacity of Walney 1 and 2: 367.2 MW 320,000 homes or one and a half times the number of households in Cumbria could be provided with clean electricity from Walney 1 & 2.

Managing the installation of a wind farm takes a lot of pulling the right strings at the right time. Foundations project manager Rasmus Miller tells about his constant focus on optimization.

By Anne Korsgaard
When you take a bird’s eye view of the Walney 2 site in Barrow during installation of one of the 51 foundations, it looks like a beehive. An ordinary working day at the Walney project involves more than 170 people in action onshore and offshore; some of them operating the vessels that work in the open sea doing the actual installing, some preparing foundations with final assembly (end plugs, generators onshore, etc) in the harbor or busy steering the cranes loading the material onto the barges. Add a good handful of project engineers from DONG Energy in charge of coordinating the many subcontractors, and you have a lot of activity.

Project manager Rasmus Miller is in charge of the 35 foundations related contracts of the Walney Windfarm Project. He juggles millions of pounds sterling when he decides on every little detail of the foundations for the Walney 1 and 2 wind farms. And he is always interested in ways to cut costs.

- We are always on the lookout for possibilities to optimize the construction without compromising the quality or safety, explains Rasmus Miller. He divides his working life between DONG Energy in Copenhagen, Barrow in the UK, Lubmin, Rostock, and meetings with deliverers mainly in Northern Europe. He visits the Walney site between once and twice a month for a three day period.

In Walney 2, a conical transition piece is used instead of the traditional cylindrical one. This way the axial bearing capacity is increased. Illustration: DNV

Lessons learned from earlier projects
One of the biggest challenges for monopile foundations is the grouting of the concrete between the transition piece and the monopile in cylindrical monopile constructions. At Walney 2 they try to cope with this in a new way:

- Several wind farms have experienced grouting issues which can result in expensive repair work. In Walney 2, it has been decided to change the assembly of transition piece and monopile to a conical one instead of the traditional cylindrical solution. In this way the axial bearing capacity is in creased compared to a cylindrical connection, explains the project manager and concludes:

- Of course we and our designer Rambøll have consulted DNV (Det Norske Veritas) for advice in solving the problem, but I am still excited to see how the conical solution will perform in the future.

On large wind farm projects like Walney, even a 1% saving adds up to a considerable amount of money. And every link in the chain is subject to savings considerations.



- For Walney 2, we have decided to simplify the construction by omitting the J-tubes that would normally encapsulate the cables on the inside of the monopile. Now the cables hang freely and it saves money on material costs and is expected to reduce construction costs. It has taken a great deal of testing and careful thought to make such a change. Now it will be interesting to follow this solution in the years to come.
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