Edda Mistral pops to Grimsby, before joining her sister out at sea

Although primarily intended for use during the operations phase of Hornsea Project One, the project team seized the opportunity to maximise its use and brought forward the Maiden Voyage so it can also be used to construct the massive wind farm.

In the construction phase, the Mistral will primarily be used by JDR Cables to complete the last step of the array cable termination, connecting the array cables to the turbine switchgear located in the transition piece.

Stuart Reid, Head of Ørsted’s East Coast Operations in the UK, said: “Hornsea Project One is a step-change in offshore wind farms in terms of scale, capacity and distance from shore. We provide offshore logistics for some of our contractors, so in this case we planned to use a vessel we already had, rather than hiring a new one. 

“I personally am very excited to see the Mistral join its sister out at sea. The Passat and Mistral are unique vessels, and proudly bear the Grimsby name on their side. They were purpose built for our operations in Grimsby, including Race Bank, and Hornsea Project One, and so it’s great that the Mistral can be used to benefit our construction team too.”

When Hornsea Project One becomes operational in 2020 it will overtake Walney Extension, officially opened by Ørsted this month, as the biggest offshore wind farm in the world. At 120km from the coastline, it will also be the furthest from shore that a wind farm has ever been built.

Lars Høy Jørgensen, Head of Operations Logistics, the team that has lead the development and delivery of the vessel, explains: “Building further offshore allows for bigger wind farms with much higher wind speeds. As a wind farms get further and further out to sea, it becomes more efficient for technicians to stay offshore for weeks at a time, rather than retuning to shore every day, a bit like oil and gas operations.

The SOVs have all the facilities needed to house technicians as they work offshore, including a gym, cinema and individual cabins that in total can sleep 60 people. A motion compensated gangway ensures safe transition to the turbines by allowing technicians to easily walk to work. “

The Mistral has already visited the offshore site for some testing, including trying out the motion compensated gangway to access wind turbines, deploying the work boat and landing a helicopter on the helipad.

Did you know? Ten facts about the Service Operations Vessel (SOV) – Edda Mistral

1. The vessels are outfitted to a similar level as cruise liner (but without a bar)!
2. A selective catalytic reduction system which uses urea (horse urine!) has helped to reduce the vessel’s NOx emissions, making it more environmentally friendly
3. An innovative power management system reduces fuel consumption of the vessels, by around 20%
4. Unlike its sister ship, the Mistral has a heli-pad – and it’s the first time a vessel equipped with a helipad will be used for regular maintenance of an Ørsted windfarm.
5. The vessel has WiFi from a 4G system set-up on the offshore substations, facilities for meetings, and everything you’d expect from a small office.
6. The meaning of “Mistral” is a strong cold north-westerly wind that blows through the Rhône valley and southern France towards the Mediterranean, mainly in winter.
7. The motion compensated gangway allows technicians to safely walk onto the wind turbines in much rougher seas than when using the traditional method of transferring from a boat. This is vital when operating at the distance from shore like Hornsea Project One where weather conditions can be more extreme.
8. The boat landing has been designed and built bespoke to fit the crew transfer vessels working on the project.
9. Ørsted first used a vessel like this for Operations and Maintenance for Race Bank offshore wind farm, which became operational earlier this year. 
10. The vessels have been supplied by Norwegian company, Østensjo Rederi, and were designed by British company Rolls Royce.