Elia modular offshore grid (MOG) project is the first of its kind offshore grid connection being developed in the Belgian waters of the North Sea.

Belgium’s high-voltage electricity transmission system operator Elia is developing the project with an estimated investment of £365m ($444m).

The project involves an offshore switchyard (OSY) platform and three subsea cables to connect four offshore wind farms, namely Rentel, Seastar, Mermaid, and Northwester 2, with the onshore grid network of Belgium.

The project received environmental permit from the government in July 2017, followed by the cable-laying permit in January 2018.

Construction works were started in June 2018, while the offshore electricity hub is set to go live in September 2019, with the start of full-fledged operations expected in 2020.

Project infrastructure

An offshore switchyard (OSY), named as the MOG platform, has been installed in the North Sea waters, approximately 40km off the coast of Zeebrugge, Belgium.

The offshore platform houses a 220kV substation and is mounted on a four-legged jacket foundation anchored 60m-deep into the sea-bed.

The 1,500 tonnes (t) jacket for the platform was placed in November 2018, while the platform’s topside was installed in April 2019.

The platform’s topside weighs 2,000t and rises 41m above the water surface. It houses a 220kV gas-insulated switchgear apart from supervisory control and data acquisition rooms, a utility room, and a diesel power facility.

The MOG platform will gather the electricity produced by the Rentel, Seastar, Mermaid, and Northwester 2 offshore wind farms, and transmit the same to Elia’s onshore grid network through three 28cm-diameter subsea cables connecting the 380kV Stevin high-voltage substation in Zeebrugge.

The total installed capacity of the four wind farms will be 1,030MW.

Two of the subsea cables will originate from the MOG platform, while the other will originate from the Rentel offshore platform. The MOG platform is connected with the Rentel platform through 5km of subsea cable, as part of the Elia modular offshore grid project.

The respective wind farm developers are, however, responsible for connecting the Seastar, Mermaid, and Northwester 2 wind farms with the MOG platform.

Details of the wind farms connected by Elia modular offshore grid

Rentel, a 309MW offshore wind farm developed by Otary Offshore Energy, became fully operational in December 2018, while Northwester 2 is a 219MW project being developed by Parkwind and Sumitomo and is scheduled for commissioning in early-2020.

The 252MW Seastar and the 235MW Mermaid wind farms also being developed by the Otary Offshore Energy consortium as part of the SeaMade offshore wind farm project and are scheduled for commissioning in 2020.

The Elia modular offshore grid project development follows a modular approach to align its construction works with the time schedules of individual wind farms, thus facilitating project realisation in a phased manner.

Contractors involved

Ramboll was contracted to provide the detailed design of the MOG platform in December 2016, while Heerema Fabrication Group was selected for the construction of the jacket structure as well as the platform topside in February 2018.

EEW Group was contracted to supply main tubular steel components and piles for the platform, while Siemens was selected to provide the gas-insulated substation.

The platform installation works were carried out by Seaway Heavy Lifting.

Dredging International, which is a part of DEME Group, was contracted for the supply and installation of 85km of submarine cables in August 2017. Hellenic Cables was subcontracted by   DEME for the supply of cables.

MOG II project details

Elia also plans to expand its offshore grid network by developing the MOG II project to connect new offshore wind farms in the Belgian North Sea. Elia targets the wind farms to be developed under the Belgian Government’s Marine Spatial Plan (MSP) 2020-2026.