Partnering with WREN, questionnaires are sent to offshore wind energy developers around the world who are involved in environmental monitoring. This page provides contextual project information and highlights environmental monitoring, providing links to available data and reports. Content is updated annually.

Hornsea 3

Description

Hornsea 3 is currently under construction in the North Sea and will be the world’s largest offshore wind farm when completed. It represents the third phase of Ørsted’s Hornsea offshore wind zone, following Hornsea 1 and Hornsea 2. When Hornsea 3 comes online with its ~231 turbines, the combined capacity of Hornsea 1, 2, and 3 will exceed 5 GW, making it one of the world’s largest offshore wind zones. Once completed, Hornsea 3 will be capable of generating enough renewable electricity to power more than 3.3 million UK homes.

The wind farm is developed and operated by Ørsted, which maintains the project from its East Coast Hub in Grimsby, England. Ørsted has partnered with Apollo Investment Corporation, which holds a 50% stake in Hornsea 3, forming a joint venture to share ownership and investment responsibilities.
 

Location

Hornsea 3 is located 160 km off the Yorkshire coast in the North Sea. The farm covers 696 square kilometres. The landfall site for Hornsea 3 is at Weybourne in North Norfolk. 

Project Timeline

  • Dec 2023: Ørsted takes final investment decision on Hornsea 3 offshore wind farm
  • Nov 2025: Ørsted signs agreement to divest 50 % stake in Hornsea 3 to Apollo
  • Dec 2023: Ørsted took final investment decision on Hornsea 3 offshore wind farm
  • Dec 2020: Planning Inspectorate granted development consent
  • June 2018: DCO application accepted by the Planning Inspectorate for examination.
  • May 2018: Submitted development Consent Order (DCO) application
  • Mar 2018: Carried out focussed statutory consultation on a number of minor amendments to the onshore route based on further feedback.
  • Nov-Dec 2017: Carried out further statutory consultation on some proposed changes in response to feedback.
  • July-Sep 2017: Carried out statutory consultation on PEIR and third round of Community Consultation Events (Phase 2)
  • July 2017: Published Preliminary Environment Information Report (PEIR), presenting the results of initial assessments to inform consultation.
  • Mar 2017: Held second round of Community Consultation Events (Phase 1.B)
  • Dec 2016: Scoping Opinion received from Planning Inspectorate.
  • Nov 2016: Held first round of Community Consultation Events (Phase 1.A)
  • Oct 2016: Published Scoping Report, containing early information about the project and assessments that would be undertaken.
  • Sep 2016: Published Statement of Community Consultation, marking the start of public consultation.
  • Aug 2015: Ørsted acquired the rights to develop the Hornsea Zone with the acquisition of Smart Wind Ltd 

Licensing Information

Hornsea 3 underwent a consenting process under the UK’s Planning Act 2008, culminating in a Development Consent Order (DCO) granted by the Secretary of State for Business, Energy and Industrial Strategy in December 2020. The planning and environmental review was led by the UK Planning Inspectorate, which carried out an Environmental Impact Assessment (EIA) examination from October 2018 to April 2019. Ørsted worked closely with RPS Group, the lead EIA consultant, to address a broad range of onshore and offshore ecological, biological, and physical impacts.

During consents, Ørsted committed to specific mitigation measures, including artificial nesting structures for kittiwake seabirds, which are embedded in a Kittiwake Implementation Management Plan (KIMP) as part of the DCO. A subsequent non-material change to the DCO was approved in 2023, adjusting how long these nesting structures must remain in place before turbines can operate. The consenting timeline, from application submission in May 2018 through examination, requests for additional information, and final decision spanned around two and a half years.

Key Environmental Issues

Hornsea 3 presents several environmental challenges, especially for benthic habitats, marine mammals, and seabirds. Survey data show the site supports a variety of seafloor communities, from worms and bivalves in mixed sediments to more mobile species like starfish and sea urchins, which could be disturbed by construction.

Construction noise, particularly from piling, may affect marine mammals. Hornsea 3’s Environmental Statement includes detailed assessments of risk (such as temporary and permanent hearing threshold shifts), along with mitigation through soft-start piling and long‑term monitoring.

The project also posed risks to black‑legged kittiwakes, a vulnerable seabird whose population may be affected by collision mortality. To address this Ørsted has built three bespoke artificial nesting structures about 1 km offshore of East Suffolk (near Minsmere and Lowestoft), designed in collaboration with Natural England, the Royal Society for the Protection of Birds (RSPB), and the Marine Management Organisation (MMO); each structure can host around 500 breeding pairs and is fitted with predator‑resistant features, remote monitoring, and observation panels. These structures are part of a long‑term monitoring plan to support the kittiwake population.

For the latest updates, visit Hornsea 3’s document library and the Planning Inspectorate’s website.

Environmental Monitoring: Hornsea 3

Searches description, design and methods, and results.
Phase Stressor & Receptor Design and Methods Results Publications Data
Baseline Birds Boat-based visual surveys, acoustic monitoring, and aerial visual surveys
Visual line-transect surveys across the former Hornsea Zone for Project One and Project Two plus a 4 km buffer and the former Hornsea Zone plus a 10 km buffer between March 2010 to February 2013.

Monthly aerial surveys commenced April 2016 along 20 parallel transects aligned north to south within the Hornsea Three array area and a 4 km buffer. 		Ongoing
The data indicate that Hornsea Three does not represent an area of significant importance for breeding, passage or wintering seabirds. 		RPS group 2018, NIRAS 2016, Dong Energy and RPS Energy 2016

No data publicly available
Baseline Fish Trawl surveys
Fish and shellfish were assessed from desk-based review of literature and otter trawl and epibenthic beam trawl surveys conducted across the former Hornsea Zone between 2010 and 2012. 		RPS group 2018, Dong Energy and RPS Energy 2016

No data publicly available
Baseline Invertebrates Benthic grab and drop camera surveys
Subtidal benthic habitats were sampled via combined benthic grab and drop down video (DDV) surveys and epibenthic beam trawl surveys in 2010, 2010/2011, and 2012. 		Ongoing
Epifaunal communities were sparse across the Hornsea Three array area and typically consisted only of echinoderms. No potential Annex I reef habitats were identified. Sediments and associated benthic communities corresponding with the Hornsea Three array area are similar to those that are present across the Project One and Project Two array areas. 		RPS group 2018, NIRAS 2016, Dong Energy and RPS Energy 2016

No data publicly available
Baseline Marine Mammals Boat-based visual surveys, acoustic monitoring, and aerial visual surveys
Visual line-transect surveys across the former Hornsea Zone for Project One and Project Two plus a 4 km buffer and the former Hornsea Zone plus a 10 km buffer between March 2010 to February 2013.

Acoustic surveys to identify harbor porpoise and dolphins were conducted monthly with of a towed hydrophone and on-board recording. The hydrophone was deployed continuously during surveys for the first six months but was not towed south of 53.83 N.

Monthly aerial surveys commenced April 2016 along 20 parallel transects aligned north to south within the Hornsea Three array area and a 4 km buffer. 		Ongoing
While five marine mammal species were identified as important in terms of conservation (harbour porpoise, white-beaked dolphin, minke whale, harbour seal, grey seal) only harbour porpoise, harbour seal and grey seal are Habitats Directive Annex II species (i.e., requires the designation of special areas of conservation). Harbor porpoise accounted for 85% of sightings during surveys. Mean encounter rates peaked May-July and was lowest in winter months. Because they are historically sighted along inshore areas, they are likely to occur within the proposed Hornsea Three offshore ECR corridor search area. Harbor seals accounted for 2% of sightings during surveys. There were sightings in most months but fewer in November and December. Tagged animals regularly travel to areas along the southern edge of the former Hornsea Zone plus 10 km buffer. Historic records and the proximity to known breeding colonies suggest harbor seal will regularly occur within the proposed Hornsea Three offshore ECR corridor search area. Grey seals accounted for 3.3% of sightings during surveys. Encounter rate decreased September-December, coinciding with the main haul-out period, and peaked in July and February. Historic records and the proximity to known breeding colonies suggest grey seals will regularly occur within the proposed Hornsea Three offshore ECR corridor search area. 		RPS group 2018, NIRAS 2016, Dong Energy and RPS Energy 2016

No data publicly available
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