One giant leap for renewables

A look at Masdar-backed London Array, the giant UK offshore wind farm.

A sea-level view of London Array.
A sea-level view of London Array.

The world’s largest offshore wind farm was formally inaugurated last month in Kent, England. The London Array consists of 175 turbines and is capable of generating 630MW of power. According to the project’s backers, which include Abu Dhabi-based Masdar, that’s enough to power around half a million homes.

An array of VIPs were present to witness the inauguration of a project that represents a key pillar of Britain’s renewable energy strategy. Under the 2009 Renewable Energy Directive, the country has a target to achieve 15% of its energy consumption from renewable sources by 2020. Wind, something that the UK has in abundance, is set to play a considerable part in achieving that goal.

“We firmly believe that electricity from renewable sources has a vital part to play in helping us deliver energy in a way that is sustainable, affordable and secure,” said Tony Cocker, chief executive officer of E.ON UK, which owns 30% of London Array. “That’s why, as we learn and improve from each wind farm that we build, we’re aiming to reduce the cost of offshore wind by 40% by 2015.”

London Array has been built approximately 20km off the coasts of Kent and Essex, and covers an area of 90km². It includes 175 turbines with a combined capacity of 630MW.

A possible second phase could add enough capacity to bring the total to 870MW. The project’s partners are Dong Energy, with 50%, E.ON (30%) and Masdar (20%).

Planning of London Array began in 2001 and applications for planning permission were submitted in 2005. Consent for the offshore works was given in December 2006 and for onshore construction in August 2007.

Construction on the onshore substation at Cleve Hill started in July 2009 and was completed in October 2012. Offshore construction started in March 2011, when the first of 177 foundations was placed in the sea bed.

The first turbine was installed in January 2012, first power was achieved in October that year and the final turbine was installed in December 2012. The project was fully operational by Spring 2013, with the formal inauguration following on July 4.

Building London Array was, of course, a major undertaking. The distance from shore, the high winds and unpredictable sea conditions all presented challenges.

The key elements involved offshore were foundations, to secure the wind turbines to the sea bed; the turbines themselves; array cables, to connect groups of turbines together and to the offshore substations; offshore substations, to boost the electricity voltage before it is sent to shore; and export cables under the sea, to connect the offshore and onshore substations.

About London Array
- Covers an offshore area of 100km²
- 630MW of electricity
- 175 wind turbines
- Built 20km off the east coast of England
- Water depth varies from 0 to 25 metres
- Nearly 450km of offshore cabling
- Two offshore substations
- One onshore substation
- CO2 savings of 925,000 tonnes a year
- Additional 240MW planned for phase two

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Offshore construction activities have been managed from a temporary construction base at the Port of Ramsgate. The base may also be used in phase two if it receives the go ahead.

Most of the contactors and suppliers appointed to the project were foreign, something that has been criticised in the UK press. Per Aarsleff and Bilfinger built and installed the turbine foundations, and installed the turbines. The turbines were supplied by Siemens Wind Power.

Offshore substations were built by Future Energy, a joint venture between Fabricom, Lemants and Geosea. Installation of offshore and onshore substations’ electrical systems was carried out by Siemens Transmission and Distribution.

Export cables were produced by Nexans Norway and array cables by JDR Cable Systems. Cables were installed by Visser & Smit Contracting and the specialist vessels used in the project were supplied by MPI and A2Sea.

Permission to go ahead with a second phase of the project was applied for in October 2012. Phase two would see another 240MW of capacity added, taking the overall total to 870MW.

London Array’s proposal for phase 2 covers an area of over 40km² along the eastern boundary of the Phase 1 area. The extra 240MW added in phase two would meet the annual electricity needs of around 180,000 homes.

The Department of Energy Climate Change (DECC) and the Marine Management Organisation (MMO) are the two bodies whose consent must be given for phase two to go ahead. To obtain permission, London Array must satisfy the same condition that was placed on phase one: that a protected bird population will not be adversely affected.

If permission to build phase two is given and capacity is increased to 870MW, London Array will then be able to power 650,000 UK homes.

The project is not, of course, without its critics. Environmental concerns, particularly the threat to bird species, led to the farm’s original location being moved slightly. Phase two will apparently not go ahead until phase one’s impact on bird populations has been rigorously assessed.

The loudest criticism relates to the subsidies being given to the project. Compared with conventional means, it reportedly costs three times more to generate energy by wind power. The current UK market price of electricity is about GB £50 per megawatt hour (MWh). London Array’s owners could receive as much as GB £90 in government subsidies for every MWh of electricity generated.

London Array’s promoters contend that the cost will fall over time. Benj Sykes, country manager for Dong Energy’s UK wind business, said: “As we now look to our pipeline of future projects, Dong Energy is determined to drive down the costs of our offshore wind farms to €100 (GB £86) per megawatt hour for projects we’ll be sanctioning in 2020.”

However the sums work out, and whether or not phase two goes ahead, Masdar is certainly proud of its involvement. Speaking at the inauguration of phase one, Dr Sultan Ahmed Al Jaber, CEO of Masdar, said: “This inauguration is a historic milestone for the United Kingdom and the development of renewable energy. Projects like London Array demonstrate the economic opportunity of large-scale renewable energy projects – from the direct investment they attract to the industries they strengthen.”

London Array: Principal contractors
Construction of wind turbines:
Siemens Wind Power
Installation of wind turbines: Per Aarsleff and Bilfinger Ingenieurbeau
Construction and installation of foundations: Per Aarsleff and Bilfinger Ingenieurbeau
Construction of offshore substations: Future Energy, a joint venture between Fabricom, Lemants and Geosea
Installation of offshore and onshore substations’ electrical systems: Siemens Transmission and Distribution
Production of export cables: Nexans Norway
Production of array cables: JDR Cable Systems
Installation of all cables: Visser & Smit Contracting
Supply of vessels: MPI and A2Sea


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