Project profile: Walney Extension Offshore Wind Farm, Cumbria

On 7 September 2018, Danish energy company Ørsted officially opened its Walney Extension offshore wind farm on the Cumbrian coast in Barrow, north-west England. The 659MW project is the world’s largest offshore wind farm, covering an area of 145km2 in the Irish Sea


Offshore wind farm


Construction complete







The 659MW Walney Extension is owned by Ørsted (50%) and its partners, the Danish pension funds PKA (25%) and PFA (25%).

Featuring 87 wind turbines and covering an area of 145km2 in the Irish Sea, Walney Extension will be able to generate clean energy sufficient enough to power nearly 600,000 homes in the UK.

Walney Extension is Ørsted’s 11th operational offshore wind farm in the UK that is equipped with 47 MHI Vestas 8MW wind turbines and a further 40 Siemens Gamesa 7MW wind turbines.

With the opening of Walney Extension, Ørsted’s total capacity operating out of Barrow has reached up to 1.5GW.

The wind farm will have a life span of approximately 25 years and is built and operated as per the UK’s Electricity Market Reform (EMR) FID-enabling regime.

Walney Extension project details

The wind farm received approval from the Secretary of State for Energy and Climate Change in November 2014. The wind farm was developed in two phases of 330MW each.

DONG Energy (now Ørsted) 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 project is expected to help DONG Energy to achieve 6.5GW of installed capacity online by 2020.

Walney Extension construction

Ørsted 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 began in early 2016.

Installation of foundations was completed in 24 months, while safety zones were 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 turbines

The wind farm comprises MHI Vestas V164-8.0MW turbines and Siemens SWT-7.0-154 7MW offshore turbines. The three-bladed V164-8.0MW model features horizontal split drive train, permanent magnet generator and a 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 Siemens B75 blade, providing a swept area of 18,600m². The power is regulated using pitch control with variable speed mechanism.

Power transmission from Walney Extension

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

The onshore cables 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 onshore substation covers an area of 28,900m², situated to the east of the NGET Middleton substation. It features switchgear and transmission systems required to carry electricity from the offshore wind farm to the grid.

The substation is equipped with 400kV/220kV/16kV onshore transformers, 220kV reactors, high-voltage gas-insulated switch gear systems, static VAR compensators  or static synchronous compensator and harmonic filters.

Contractors involved in Walney Extension

MHI Vestas Offshore Wind delivered wind turbines for the first phase of the Walney Extension, in February 2015.

In March 2015, DONG Energy selected Siemens for the supply of 7MW wind turbines for the second phase of the wind farm.

Cover image credit: Ørsted/DONG Energy