TenneT has signed multi-year framework agreements with Allseas and Heerema Marine Contractors for transporting and installing at least fourteen offshore platforms, each with a capacity of 2 gigawatts (2GW). The fourteen 2GW converter stations will be installed in the Dutch and German North Sea. The framework agreement includes at least 28 slots by 2031: fourteen slots for the transport and installation of a jacket (substructure of the offshore converter station) and fourteen slots for the transport and installation of the superstructure (topside).

Renowned and some of the world’s largest installation ships

Heerema will use the semi-submersible crane vessel (SSCV) Sleipnir as well as its own “Floatover” barge. Allseas will use the world’s largest installation vessel, the Pioneering Spirit, to install the jackets and topsides.

Tim Meyerjürgens, COO at TenneT: “With this agreement, we guarantee our HVDC partners the timely transport and installation of our offshore platforms. With a view to the future, we are expanding strategically important transport capacities. We are proud to have signed this framework agreement with our Dutch and Swiss-Dutch partner companies. These European partnerships prove once again that the energy transition is a joint effort. As market leaders in offshore transport and installation, they have the necessary know-how and equipment to carry out projects of this magnitude safely and successfully.”

Both ships have been used several times in recent years to install jackets and topsides for TenneT in the Dutch and German North Sea. The Pioneering Spirit installed the DolWin kappa in the German North Sea in September 2022. Heerema was awarded around 60% of the available slots of the total contract, while Allseas was awarded the remaining 40%. Within the framework agreements concluded further orders for future TenneT offshore projects can be awarded. Additionally, defined slots are not tied to any specific 2GW projects. The HVDC suppliers who manufacture the individual offshore converter stations for TenneT (Hitachi Energy/Petrofac, GE/Sembcorp, GE/McDermott and Siemens/Dragados) can choose among the suppliers.

Boskalis will subcontract to Allseas to build one or two new transport vessels specifically for the 2GW program. These ships will meet the latest sustainability and emissions norms and standards.

High willingness to invest

TenneT recently awarded framework contracts for constructing land stations in the Netherlands, the offshore and onshore converter stations and the cable systems of fourteen 2GW projects in both countries. An investment volume of more than 35 billion euros. The newly developed approach of awarding tenders as comprehensive framework agreements for several projects accelerates the basic process and, ultimately, the grid expansion.

Marco Kuijpers, Director Large Projects Offshore at TenneT: “With the long-term framework agreements, we offer our partners a strong basis for the successful implementation of our projects. These contracts give our suppliers the planning security they need to further expand capacities and make targeted investments.”

Pieter Heerema, President of Allseas, said: “We are delighted that Allseas’ ‘single-lift’ technology has been selected to support TenneT in the realisation of the ambitious 2GW program and to play a key role in the energy transition in Europe. When my father, Edward Heerema, developed the single lift concept in 1987, no one could have guessed that four decades later, it would be used on a landmark offshore project of such strategic importance. Pioneering Spirit’s unique transport and installation capability has been used with great success to deliver key equipment for offshore wind power projects across Europe. The unique capabilities of this world’s largest installation vessel make it possible to carry out installations throughout the year. This gives us maximum flexibility in the extensive and complex construction schedules. We look forward to deepening our relationship with TenneT with this prestigious project.”

Heerema’s Chief Commercial Officer, Jeroen van Oosten added: “We are proud to partner with TenneT to deliver clean energy for the Netherlands and Germany. The award of this framework contract is an important example of the advantages of a trusting partnership between clients and contractors. To ensure that clean energy needs are met, there should be an increasing focus on collaborative, forward-looking agreements. Agreements that also strategically address the need for transportation and installation capacity.”


Belgium, Denmark, Germany, the Netherlands, France, Ireland, Luxembourg, Norway and the United Kingdom signed the Ostend Declaration at the North Sea Energy Summit in April 2023: the countries agreed to collectively generate at least 120 gigawatts (GW ) to be installed at offshore wind power capacity. TenneT, Europe’s leading offshore transmission system operator, will provide around a third of this volume, specifically 40 GW, through its offshore grid connection systems. To this end, TenneT will build further offshore projects in Germany and the Netherlands in the coming years, each with a capacity of 20 GW.

Source: https://www.tennet.eu/
Image source: Courtesy of TenneT

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