London Array

Location and Site Details

The London Array offshore wind farm is situated approximately 20 kilometers off the coast of Kent and Essex, in the outer Thames Estuary, UK. It is spread over an area of about 100 square kilometers between two sandbanks, Long Sand and Kentish Knock, in waters that are approximately 25 meters deep.

Ownership and Operation

The London Array wind farm is owned and operated by London Array Limited, a consortium comprising:

• RWE (previously E.ON) with a 30% stake
• Ørsted (previously DONG Energy) with a 25% stake
• La Caisse de dépôt et placement du Québec with a 25% stake
• Masdar with a 20% stake.

Capacity and Turbines

The wind farm features 175 Siemens Gamesa SWT-3.6-120 wind turbines, each with a rated output of 3.6 MW. These turbines have a 120-meter diameter rotor with 58.5-meter long blades, resulting in a swept area of 11,300 square meters. Each turbine stands 147 meters tall from the water surface to the tip of the blade and is mounted on a 67-meter long monopole foundation. The turbines are arranged in rows and columns aligned with the prevailing south-westerly winds, spaced 650 to 1,200 meters apart.

Power Generation and Transmission

The London Array has an installed capacity of 630 MW, which is enough to power approximately 560,000 to 584,000 UK homes annually. It displaces around 900,000 tonnes of CO2 each year.

The electricity generated by the turbines is collected through a network of approximately 200 kilometers of 33kV inter-array undersea cables and transmitted to two identical offshore substations. These substations step up the voltage to 150kV before it is exported to shore via four high-voltage undersea export cables. The electricity is then transmitted to the Cleve Hill onshore substation in north Kent, where it is stepped up to 400kV and fed into the National Grid transmission network.

Construction and Development

Construction on the London Array began in July 2009 with the onshore works, followed by the start of offshore construction in March 2011. The first power from the wind farm was generated in October 2012, and the installation of the last turbine was completed in December 2012. The project was officially inaugurated by Prime Minister David Cameron on July 4, 2013.

The project was initially planned to be developed in two phases, with a total installed capacity of 1 GW. However, the second phase, which would have added an additional 370 MW, was canceled in 2014 due to concerns about the impact on certain bird species.

Environmental Considerations

The development of the London Array was notable for its rigorous environmental impact assessments and conservation efforts. Extensive environmental studies began in 2001, and the project received various planning consents and licenses. The project was designed to maintain a healthy marine ecosystem, and significant efforts were made to protect and conserve the marine biodiversity of the project site.

Contractors and Financing

Several contractors were involved in the project:

• Siemens Gamesa provided the turbines and electrical equipment for the offshore substations.
• A joint venture between Per Aarsleff and Bilfinger Berger supplied the monopole foundations for the turbines and the offshore platforms.
• A consortium of MPI and A2SEA provided marine crew and vessels for the installation of foundations and turbines.
• Future Energy, a joint venture between Fabricom, Lemants, and Geosea, was responsible for the design, construction, and installation of the offshore substations.

The project received financial backing from the European Investment Bank (EIB), which provided a £250 million loan guaranteed by the Danish Export Credit Agency EKF.

Operations and Maintenance

The wind farm is maintained and operated from the Port of Ramsgate. James Fisher Marine Services (JFMS) was appointed to deliver the balance of plant (BoP) operations and maintenance (O&M) services for the turbines and the meteorological mast, as well as statutory inspection services for the offshore substations. Worley was contracted to provide statutory inspections and general maintenance services for the wind-turbine-generators.

Transmission Assets

The transmission assets of the London Array are owned by a consortium known as Blue Transmission London Array Limited, which purchased these assets in September 2013 under Ofgem’s Offshore Transmission Owner (OFTO) regime. London Array Limited provides operations and maintenance services for these transmission assets.

In summary, the London Array offshore wind farm is a significant contributor to the UK's renewable energy landscape, setting a precedent for large-scale offshore wind projects and continuing to be a leader in innovation and environmental stewardship.