The 660MW Walney Extension Offshore Wind Farm will be located off the Cumbrian coast in the UK. Credit: DONG Energy.
The Walney Extension offshore wind farm will include up to 90 turbines. Credit: DONG Energy.
The first phase of the Walney Extension will be installed with V164-8.0MW wind turbines. Credit: MHI Vestas Offshore Wind.

The 660MW Walney Extension Offshore Wind Farm will be located in the Irish Sea, approximately 19km off the coast of Cumbria in the UK, neighbouring the 367.2MW Walney Offshore Wind Farm. DONG Energy is the developer of the wind farm extension.

Once operational in 2018, the Walney Extension will overtake the 630MW London Array Offshore Wind Farm as the world’s biggest offshore wind farm. It will generate enough electricity to power more than 460,000 UK homes.

Walney Extension project details

25 3.6MW wind turbines have been installed at the 90MW Burbo Offshore Wind Farm in Liverpool Bay, Wales.

The proposed Walney Extension offshore wind farm received approval from the Secretary of State for Energy and Climate Change in November 2014. The wind farm will be developed in two phases of 330MW each.

DONG Energy secured all permits from relevant authorities and concluded site assessments as well as supply and installation contracts for the wind farm before the announcement of the final investment decision (FID) in October 2015.

The wind farm will have a life span of approximately 25 years. It will be built and operated according to the UK’s Electricity Market Reform (EMR) FID-enabling regime with a determined price for the first 15 years of output.

The project is expected to help DONG Energy achieve 6.5GW of installed capacity online by 2020.

Walney Extension construction

DONG Energy broke ground on the Walney Extension project with the start of construction on the onshore substation in Heysham in August 2015. The onshore substation construction is a vital element of the preliminary works for the project.

Offshore construction is planned to begin in early 2016. Installation of foundations is expected to be completed in 24 months, while safety zones will be created for construction vessels and turbines during the construction.

The wind farm is expected to create more than 500 new jobs in the UK, during the main construction phase between 2016 and 2019.

Walney Extension wind farm make-up

The wind farm will be installed with MHI Vestas V164-8.0MW turbines and Siemens SWT-7.0-154 7MW offshore turbines. The three-bladed V164-8.0MW model features a horizontal split drive train, permanent magnet generator and full-scale converter. The turbine has a rotor diameter of 164m and swept area of 21,124m².

The SWT-7.0-154 turbine incorporates simplified design and Siemens direct drive technology for reliable and cost-efficient operation. The 154m-diameter rotor is fitted with a Siemens B75 blade, providing a swept area of 18,600m². The power is regulated using pitch control with a variable speed mechanism.

Power transmission from Walney Extension

The power generated by the wind farm will be transmitted through subsea export cables extending from the offshore substations to landfall. Each high-voltage AC cable will have a voltage between 132kV and 220kV.

The onshore cables will extend from landfall, close to Middleton Sands, to the onshore substation. Each cable will be installed underground and joined to the offshore export cable at the transition joint bays located in the neighbourhood of the landfall.

Onshore substation details

“The wind farm is expected to create more than 500 new jobs in the UK, during the main construction phase between 2016 and 2019.”

The onshore substation will be constructed on an area of 28,900m², which will be situated to the east of the proposed NGET Middleton substation. It will feature switchgear and transmission systems required to carry electricity from the offshore wind farm to the grid.

The substation will be equipped with 400/220/16kV onshore transformers, 220kV reactors, high-voltage gas-insulated switch gear systems, static VAR compensators (SVC) or static synchronous compensator (STATCOM) and harmonic filters (HF).

Contractors involved in Walney Extension

MHI Vestas Offshore Wind was chosen by DONG Energy to deliver wind turbines for the first phase of the Walney Extension in February 2015.

In March 2015, DONG Energy selected Siemens for the supply of 7.0MW wind turbines for the second phase of the wind farm.