Making 2 GW the new standard for HVDC offshore wind connections

28 April 2023

Significant new milestones have been achieved by TenneT and Amprion in developing standardised 2 GW HVDC connections for offshore wind.

Above: Visualisation of Amprion 2 GW HVDC offshore wind converter platform (Source: Amprion GmbH)

Amprion Offshore GmbH has awarded Siemens Energy and Dragados Offshore HVDC converter station contracts for the BalWin 1 and 2 (formerly called LanWin 1 and LanWin3) HVDC offshore grid connection systems.* They will have a capacity of 2 GW, and the contract is described by Siemens Energy as the “world’s first order for a 2 GW grid connection at sea.” The new 2 GW standard represents a doubling of capacity in comparison to the previous de facto 900 MW HVDC standard typically seen in offshore wind connections and almost triple the 700 MW typical of AC offshore wind connections.

Siemens Energy and Dragados will build two converters offshore and two onshore, with commissioning two and three years earlier, respectively, than originally planned.

Due to the acceleration measures planned by the German government, Amprion Offshore invited tenders for the construction of the converters earlier than planned, in the autumn of 2022. The plans provide for BalWin 1 to go into operation as early as 2029, instead of 2031, and for BalWin 2 as early as 2030 instead of 2033. With only three months to tender and award the contract, Amprion says it was “able to complete the process in record time”, noting that “the experience from previous contracting processes has been an important factor.”

The contract is worth a total of more than €4 billion including maintenance for ten years and represents the largest offshore grid connection order in Siemens Energy’s history, the company says.

“We are working at high pressure to meet the accelerated scenarios of the German government to install 30 GW of offshore wind energy by 2030. That is why we are very pleased to have... two partners in Siemens Energy and Dragados Offshore who can implement our converters quickly and reliably,” said Peter Barth, joint managing director of Amprion Offshore GmbH.

Last summer, Amprion had already commissioned the Spanish–German consortium to build the converters for DolWin 4 and BorWin 4. The companies have promised an accelerated start-up for BorWin 4, with operation brought forward by one year. Amprion says it is particularly pleased that an even greater acceleration has now been promised for BalWin 1 and 2: “The market is currently extremely tense. In particular, the required shipyards for converter platforms are deficient in Germany and Europe. That is why two or three years of acceleration are an enormous challenge,” said Dr Carsten Lehmko¨ster, who is managing director of Amprion Offshore GmbH together with Barth.

The BalWin 1 and 2 connection systems will connect offshore wind farms in the North Sea to the German onshore transmission grid, at Wehrendorf (Lower Saxony) and Westerkappeln (North Rhine-Westphalia). They will be installed in parallel to one another for the most part on land and at sea.

BalWin 1 and 2 will have a route length of nearly 400 km, with around 170 km subsea. The land sections of both BalWin 1 and 2 will be underground DC cables.

TenneT’s 2 GW strategy

Dutch–German TSO, TenneT is also aiming for a programme of 2 GW HVDC offshore wind connections, and has recently entered into an “early works agreement” with its partners Hitachi Energy and Petrofac.

“The early works agreement with Hitachi Energy and Petrofac is a very important milestone in the execution of our 2GW strategy”, said Marco Kuijpers, director, offshore at TenneT. With this first agreement we are reserving production capacity for platforms and HVDC equipment and initiating the detailed engineering process to secure the time schedule for two [Dutch] 2 GW projects, IJmuiden Ver Alpha (2029) and Nederwiek 1 (2030). We expect to award the full framework contracts for the HVDC platform scope of all the 2030 Road Map projects in the first quarter of 2023, along with the other envisaged partners.”

TenneT has also named land station civil contractors for the Dutch 2 GW projects. Dura Vermeer, BAM Infra Nederland and Visser & Smit Bouw have entered into a “framework agreement”, having been selected “on the basis of quality, safety and sustainability”, said TenneT.

The design phase of the land stations, where 525 kV DC is converted to 380 kV AC, has started, Routes of BalWin with first delivery of civil engineering works 1and2HVDC expected in 2026.

At least eight Dutch land-based converter stations for offshore wind are expected to be realised by 2030, with the framework agreement extendable for new 2 GW projects announced 12 within the term of the contract.

Marco Kuijpers said: “On safety and 10 sustainability, the parties that have made progressive proposals to work as safely and sustainably as possible have been selected. For example, the roofs of buildings are built on the ground and then installed as a whole, reducing the need to work at height. To fulfil the ambition 6 of ‘TenneT’s most sustainable land station’, the parties were selected for their sustainability 1 expertise. Thus, already during the design phase, the biggest polluting resources such as steel and concrete are minimised and replaced by a sustainable alternative. These include wood and recycled concrete. By looking at the entire life cycle of the building, the least amount of pollution is controlled and low-emission vehicles and equipment are used as much as possible during construction. The limited outdoor space is also designed to maximise biodiversity while maintaining a safe working

The basic design of the land stations has Converter platforms already been completed. The selected parties are now directly involved in doing the detailed design to ensure that the right solutions are chosen.

“By working jointly on the designs, we can make choices at a much earlier stage. This contributes to the standardisation of the concept and ensures that we will face fewer surprises later in the process,” said Kuijpers.

At present, TenneT’s connection capacity is around 7.2 GW in the German North Sea and around 2.8 GW in the Dutch North Sea.

TenneT believes its 2 GW programme, with its strong focus on harmonisation and standardisation, provides “a blueprint for future offshore grid connection systems and enables faster deployment.” At the same time, the larger capacity, 2 GW per system, reduces the number of grid connections required and “sets a new pace for the European energy transition.”

TenneT says it is on course to achieve the 2030 offshore expansion target. Germany, the Netherlands, Denmark and Belgium have agreed to install at least 65 GW of offshore wind jointyly by 2030, announced as part of the inter-governmental Esbjerg Declaration. At 40 gigawatts, almost two-thirds of this is accounted for by TenneT, with 20 GW each in the German and Dutch North Seas. On top of this, in 2022, energy ministers from the members of NSEC (North Seas Energy Cooperation) and the European Commission announced a significant increase in their collective ambition for deployment of offshore renewable energy up to 2050.

As well its pioneering activities in laying the groundwork for the new 2 GW standard for offshore HVDC connections, TenneT is also pursuing another important area of innovation in HVDC technology, namely multiterminal and multivendor HVDC systems, with interconnection of DC projects seen as an important building block for the future transmission grid. In what it describes as “the first steps towards a DC grid”, TenneT is planning to implement a multiterminal DC hub in northern Germany, interconnecting offshore and onshore systems in a four-terminal configuration, together with its partner TSO 50Hertz.

Currently, HVDC components from different suppliers do not work well together properly and it is not proving feasible to connect together converter stations supplied by different manufactures. Together with partners, TenneT has developed a vendor-neutral standard for next-generation HVDC technology, and has asked the EU Commission to support this by granting rapid approval.

In 2021, TenneT presented what it calls the “wind power booster”, a 6 GW multiterminal/ multivendor DC hub at Heide, Germany, aimed at accelerating offshore wind expansion, enabling 6 GW of offshore capacity to be realised three years earlier than it would otherwise.

TenneT said at the time that the wind power booster was “a first concrete step towards a long-term meshed high voltage direct current grid at sea and on land.” The initiative was supported by some key players: ArcelorMittal; Entwicklungsagentur Region Heide; EWE; Holcim; Hynamics; Ørsted; Raffinerie Heide; Salzgitter AG; Uniper; BWO; and WAB.

* LanWin stands for LangeoogWind, BalWin for BaltrumWind

Visualisation of Amprion 2 GW DC to AC land converter station for offshore wind connection (Source: Amprion GmbH)
Routes of BalWin 1 and 2 HVDC connections (map: Amprion GmbH)
Tennet 2 GW HVDC offshore wind converter platform

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