Monday, 21 February 2011

Offshore Wind Farm in UK begins generating power from its first turbine

Walney Offshore Wind Farm, located 15km west of Barrow-in-Furness in Cumbria, UK, began generating power from its first turbine in January 2011. The turbine is connected to the national grid through an offshore transformer at Heysham.

The project consists of 102 turbines being installed in two phases, Walney I and Walney II. Estimated at £1bn, the project will deliver 367.2MW of combined energy sufficient to power more than 320,000 households in UK.

It is owned by Dong Energy (50.1%), Scottish and Southern Energy (SSE-25.1%) and a consortium of PGGM and Dutch Ampère Equity Fund (24.8%).

Dong Energy is the leading partner and operator of the wind farm. It has signed a 15-year long term power purchase agreement (PPA) with the consortium of PGGM and Dutch Ampère Equity Fund for the purchase of the consortium's share of electricity from the project.

The company plans to sell power purchased from the consortium and the environmental benefits received from the British Government in the local market.

Plant details

Walney is being constructed along a north-west to south-east direction. It will cover an area of approximately 73km².

Walney I and II will each have 51 Siemens turbines with a rated capacity of 3.6MW. The turbines will be 749m-958m apart and installed in rows.

Turbines installed at Walney I will have a rotor diameter of 107m and are 137m tall to the tip of the blade.

Walney II will have turbines with a rotor diameter of 120m. They will have a maximum height of 150m to the centre of the hub.

The turbine arrays will be connected by underwater sea cables to an offshore substation where the voltage will be stepped up from 34kV to 132kV before being exported to an onshore substation.

"Dong Energy is the leading partner and operator of the wind farm."

The project was initially 100% owned by Dong Energy. In December 2009 SSE acquired 25.1% share in the project, which was followed by a consortium of PGGM and Dutch Ampère Equity Fund acquiring 24.8% in December 2010.

The consortium paid £16m to acquire the share. It will also share the project construction cost on a pro-rata basis. The purchase price, however, did not include payment for transmission assets which will be owned by a separate operator in future.

Dong Energy will provide interim finance to the consortium for their share of the construction cost. PGGM / Dutch Ampère Equity Fund will provide external financing to Dong Energy upon completion of the project.


Construction of Walney I commenced in March 2010. The monopiles were laid by jack-up vessels Vagant and Goliath operated by Belgium-based GeoSea.

The first monopole was installed in April 2010. The export cable was shipped to the site at the same time.

The monopiles are placed 30m deep into the seabed. Each monopile is 56m tall and weighs 550t.

The Walney I offshore substation was placed within the wind farm area. It weighs 1,100t and was erected in June 2010.

Seajacks Kraken and Seajacks Leviathan owned by Seajacks UK have been contracted for the turbine installations in Walney I and Walney II respectively. Sea Worker, a jack-up barge operated by A2Sea, has already installed five wind turbines at the site.

The first turbine was installed in July 2010. It is now generating power for the national grid. All the turbines of Walney I had been installed by December 2010.

The construction vessel Pompei is placing stones at a radius of 15m around the foundation to mark the cable and turbine installation positions.

Walney II is scheduled to begin installations in March 2011. It is expected to come online by the end of the year.

The turbines in Walney II will be placed 25m-30m deep, which will require longer and heavier monopiles weighing up to 800t.

Onshore cabling work is underway in Cleveleys near Blackpool.

Power generated by Walney II will be brought onshore in front of Thornton gate through a 132kV underwater cable. It will be connected to a new substation which is currently under construction along the route to Hill House Industrial Estate.

The cargo ship Annette owned by SAL was contracted to deliver the monopoles to the site.

Stemat 82, a cable installation vessel, is being used to install the array cables in the seabed. The cables are placed in the J-tube and protected with a layer of rocks to prevent scouring.

Walney Wind Farm contractors

Seabed Power was awarded the contract for transporting and installing more than 92km of 33kV array cables for Walney I. The cables were supplied by the nkt cables group.

"Dong Energy plans to extend the Walney offshore wind farm by a further 750MW."
Seabed Power was also responsible for laying 44km and 43km of 132kV export cables in two different routes. The cables were supplied by Prysmian Group in a €24.5m contract. Prysmian was also awarded a €18m contract to supply similar 132kV cables for Walney II.

The offshore substation steel structures and jackets were contracted to Bladt Industries in 2009. The first set for Walney I was delivered in May 2010 while the second set is underway construction.

The aluminium hydraulic cylinders were manufactured by Holmatro.

Powerstream Electrical Services built the onshore substation at Heysham in a contract worth $1.1m in June 2010.

Other major contractors to Walney I are EEW-Special Pipes Construction (SPC) Rostock for the manufacture of 51 monopiles, Visser & Smit Marine Contracting (VSMC) for the Stemat 82 cable lay vessel, Tekmar Solutions for a cable protection system, Proserv Offshore for cleaning of the marine growth around the pile and Ledsham for the construction of an 11kV substation for Siemens.

Walney II contractors include A2Sea and Ballast Nedam for installation of the foundations, Norway-based Draka Norsk Kabel (DNK) for installing the inter-array cables and associated logistics and Offshore Marine Management (OMM) for termination and testing of inter-array cables.

Dong Energy signed an agreement with Associated British Ports (ABP) to use 18 acres of the Barrow area for handling essential components of the wind turbines during construction.

Audit of the barge and tugs used in the project is being carried by Specialist Marine Consultants.

NIRAS was contracted for a number of consultation works related to the project, including geophysical surveys, management of installations, logistics planning and so on.


Dong Energy plans to extend the Walney offshore wind farm by a further 750MW. The company signed a lease agreement with the Crown Estate in May 2010. The proposal is expected to be submitted for planning consent in 2013.

The extension is expected to cover an area of 145km². It will include one offshore substation, 33kV array cables, three core underwater offshore cables and an onshore connection point at either Heysham, Stanah or Penwortham substation.

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