North Sea to Become Europe’s Green Power Plant

With its strategy for the future expansion of offshore renewable energies, the EU Commission's targets speak a clear language: by 2030, existing capacities are to increase fivefold from 12 to 60 GW. Under the strategy, a climate-neutral EU will require as much as 340 GW of installed capacity by 2050. For these projects, the North Sea will become Europe's green power plant.

But it is important not only to expand power generation, for distribution plays a role that is at least as important. It is therefore essential that the expansion of the power grids keeps pace with the expansion of renewables.

The German transmission system operator TenneT has an offshore transmission capacity of around 7,000 MW in the German North Sea and is already working on completely new electricity distribution systems. For example, in cooperation with consortium partners, the company plans to build a so-called wind energy distribution hub in the North Sea by 2035, which, at 12,000 MW, will have the capacity of twelve large power plants.

The distribution hub will supply Denmark, the Netherlands and Germany with green wind power from the North Sea. The ingenious feature is that it connects several offshore wind farms with the countries and at the same time establishes a direct link between the countries themselves. When the wind blows, electricity from offshore wind farms is transmitted to the countries, and when the wind is calm, the same lines can be used for direct electricity trading among them.

"The energy transition and steel are an excellent match more than ever before."Guido Ludwig Regional Sales Manager Mannesmann Line Pipe

Incorporating green hydrogen

In the future, however, it will probably not be possible to use the energy from offshore wind farms via the power grid alone. There is therefore demand for power-to-X schemes and for the integration of electrolyzers for the production and storage of green hydrogen.

TenneT is convinced of the need for a systematic expansion of the gas and electricity infrastructure. Only if the production and storage of green hydrogen are properly integrated in the overall power system can they meaningfully supplement the power grid and relieve the burden on it. And only then can wind power effectively contribute to the desired energy transition and climate neutrality.

Dogger Bank, the world's biggest offshore wind farm

But back to the North Sea. The Dogger Bank is a large sandbank running east-west in the North Sea, extending from Britain via the Netherlands and Germany to Denmark. The world's largest offshore wind farm is currently being built in the British section. The potential area covers 8,660 km² and is located 125 to 290 km off Yorkshire in Northern England.

The project is being developed by a joint venture and is divided into three areas: Dogger Bank A, B and C. These will each have 1,200 MW of installed capacity and are scheduled to graduallycome on stream by the beginning of 2026.

In addition, there is the Sofia section with a further 1,400 megawatts, for which commissioning is scheduled for the end of 2026. Together, the first construction stage of the wind farm thus amounts to 5 GW, which is roughly equivalent to the output of three to four medium-sized nuclear power plants. By fully exploiting the potential area, an installed capacity of up to 13,000 MW would be feasible in the longer term.

Production of the turbines and monopile foundations

General Electric will supply a total of 277 offshore wind turbines to Dogger Bank A to C. Area C will be equipped for the first time with 87 Haliade-X 14 MW latest-generation offshore wind turbines.

The contracts for the production of the required monopile foundations and transition pieces have been awarded to a Dutch-Belgian consortium. The companies will construct all 277 monopiles and transition pieces for Dogger Bank A, B and C. One company will be responsible for the production of the monopiles and another, for its part, for the design, construction and coating of the transition pieces.

Matching tube lengths and "Beatrice expertise"

Through Salzgitter Handel in Poland, Mannesmann Line Pipe already had excellent links with the manufacturer of the transition pieces. The company has branches in Belgium, the Netherlands, the United Kingdom and Poland and has more than 50 years of experience of the engineering, construction, supply and erection of steel structures. Back in 2016, tubes from Mannesmann Line Pipe were processed here for the Beatrice Offshore Wind Farm in the northeast of Scotland.

For Dogger Bank A, the company has already fabricated the first 95 transition pieces for the installation of the monopiles in water ranging in depth from 18 to 63 m - the first have already been supplied. For the 27 m long transition pieces with a diameter of around 8 m, the boat landing design called for tube lengths of 13 and 13.30 m, each of which Mannesmann Line Pipe was able to supply in a single piece. "This eliminated hundreds of additional time-consuming and costly circular welds in the construction of the transition pieces. In addition, the surface of our Mannesmann tubes has little scaling, which in turn makes it easier to coat the tubes," says Guido Ludwig, the responsible Regional Sales Manager at Mannesmann Line Pipe, summing up the arguments decisive for the award of the contract. "In the meantime, we have supplied around 1,100 metric tons of HFI-welded steel tubes measuring 355.6 x 25 mm of grade S355J2H conforming to DIN EN 10210 via Salzgitter Handel in Poland," Ludwig adds.

Installation from mid-2022

Contracted to install the monopile foundations and transition pieces is the Belgian company Jan de Nul. The "Voltaire", only recently built to the highest environmental standards, will be used for the work. The vessel can run on second-generation biodiesel, which reduces the fuel's carbon footprint by up to 90%. The vessel also comes with a dual exhaust filter system that removes up to 99% of nanoparticles from exhaust gases and significantly reduces emissions of NOx and other pollutants with the aid of a catalytic converter. The main crane can lift loads of over 3,000 tons, enabling it to erect the current and future generations of offshore wind farms with heights of over 270 m and rotor blades up to 120 m long.

Another step toward the North Sea's green power plant

The commissioning of the Dogger Bank Offshore Wind Farm marks another step on the North Sea's path to becoming Europe's green power plant. However, to achieve the goals of the Paris Climate Agreement by 2030, many more will have to be added. Says Ludwig: "With our HFI-welded steel tubes we can help achieve these am- bitious targets. The energy transition and steel are an excellent match more than ever before."