Hornsea One is located in the North Sea, off the coast of East Yorkshire in the UK. It will be the largest offshore wind farm in the world and the first project to be built in Zone 4 of the Hornsea Development Zone. The centre of the offshore site is approximately 140 km east of the Humber Estuary and will be connected to the National Grid at Killingholme substation via a 40 km onshore route and a 145 km offshore route. The offshore export cables, landfall and connection to the onshore export cables are at Horseshoe Point, immediately south of the Humber Estuary. Hornsea One will comprise 174, Siemens Gamesa 7MW turbines and when fully operational in 2020, will provide green energy for well over 1 million homes in the UK.
DEME Offshore was awarded the contract for the transport, installation, pull-in and burial of the Hornsea One export cables by Ørsted. Late 2018, DEME Offshore successfully completed the export cable installation, which is the longest AC offshore wind cable ever to have been installed. Additionally, the cable manufacturing and installation were completed months ahead of schedule.
The world’s largest offshore wind farm was the first project for our new cable installation and multifunctional vessel ‘Living Stone’. With its 10,000-tonne cable capacity and cutting-edge dual-lane cable system, ‘Living Stone’ significantly improves cable installation production rates.
Throughout 2018, DEME Offshore installed foundations and turbines at Hornsea One. Installation vessel ‘Innovation’ carries up to four monopiles at a time. Each monopile is 65 m long, weighing around 800t and has a diameter of 8.1m.
The broad scope of work performed for this huge project included:
• Transport of offshore submarine cables from cable supplier’s facilities to the Hornsea One site
• Cable installation works (offshore cable 370.6 km & nearshore cable 82.2 km), including installation of offshore joints and pull-ins at 4 offshore platforms
• Pre-trenching works: pre-sweeping of sand dunes; pre-lay trenching backfilling (representing 2,180,000 m³)
• Landfall works: 3 cable pull-ins; post-lay burial of cables in intertidal zone over 2.6 km
• Rock works: installation of 15 pre-lay and 15 post-lay rock berms
• Crossing installation & cable burial
• Boulder removal
• Engineering Survey over the cable routes