| Transmission & distribution


The design phase of the land stations, where 525 kV DC is converted to 380 kV AC, has started, with first delivery of civil engineering works 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 within the term of the contract. Marco Kuijpers said: “On safety and 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 of ‘TenneT’s most sustainable land station’, the parties were selected for their sustainability 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 environment.”


The basic design of the land stations has 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,


Routes of BalWin 1 and 2 HVDC connections (map: Amprion GmbH)


13 12 10 9 6 1 8 11 4 V IV 7 2 I 0


Hilgen- riedersiel


Emden II 


Wilhelms- haven


3 III 0 Cuxhaven Bremerhaven Büsum


5


5 5


Denmark


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     





Bremen


 Lingen NVP Westerkappeln Netherlands  NVP Wehrendorf


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.


Above: Tennet 2 GW HVDC offshore wind converter platform


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.


www.modernpowersystems.com | March 2023 | 25


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