Cooperation to link offshore wind farms

22.09.2020

Realising the full potential of offshore wind energy in the North Sea will be crucial for the decarbonisation of the European economy and society. The transmission system operators (TSOs), whose control areas border the North Sea, are aware of this, including the Dutch-German TSO TenneT and National Grid from the UK. Both the Netherlands and the UK have set ambitious targets for their respective development of wind capacity in the North Sea. However, to achieve large-scale growth in offshore wind energy, significant amounts of new infrastructure and close cooperation between the countries around the North Sea will be essential.

On 22 September, TenneT and National Grid announced a cooperation agreement to examine the feasibility of interconnecting Dutch and British wind farms to the energy systems of both countries via submarine cables. The announcement is following a recent decision by the Dutch government to secure the first 2GW offshore transmission grids for high-voltage direct current (HVDC) in the Netherlands for the IJmuiden Ver wind farm zone, located some 80km off the Dutch north-west coast. Under the cooperation agreement, TenneT and National Grid will explore the development of a multi-purpose interconnector (MPI) to simultaneously connect up to 4GW of Dutch and British offshore wind energy between the two national electricity systems, thereby creating an additional 2GW of interconnection capacity.

By connecting to both systems, the MPI will allow the use of free transmission capacity for electricity trade between the two countries, thus improving the utilisation of offshore infrastructure – and possibly decreasing the need for additional infrastructure. This will also reduce the environmental impact on coastal communities compared to the current approach of separately developing and connecting interconnectors and wind farms. The two TSOs intend to have defined a “pathfinder project” by the end of 2021 with the aim of creating an operational system by 2029.

Manon van Beek, CEO of TenneT, comments on the agreement: “TenneT has been at the forefront of developing multi-purpose interconnection to enable the large-scale growth of offshore wind in the North Sea. This agreement allows us to work with National Grid in the North Sea to develop innovative infrastructure that uses every spare electron of offshore wind generation to reach our decarbonisation targets.”

TenneT has concluded an agreement with National Grid to investigate the interconnection of UK and Dutch offshore wind farms (exemplary picture: TenneT)

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TenneT continues offshore cost reduction with BorWin5

12.08.2020

BorWin5 is to become the 15th offshore grid connection system implemented by the Dutch-German transmission system operator (TSO) TenneT in the German North Sea, the twelfth DC connection, and the fourth offshore grid connection off the coast of the island of Borkum using HVDC transmission technology. With a total length of 230 kilometres, BorWin5 will also be the longest offshore connection of the TSCNET shareholder. The realisation of BorWin5, expected to be commissioned in 2025, is progressing well, as TenneT has now placed orders for the construction of the onshore and offshore converter stations as well as for the production and installation of the DC underground and submarine cables. The contract for the converter stations has been awarded to a consortium of Siemens and Dragados Offshore and for the cables to NKT HV Cables.

The key technical data of BorWin5 reflect TenneT’s extensive experience and expertise in the offshore sector on the one hand, and the TSO’s commitment to constantly improving established technology on the other. For example, BorWin5 is the second project, after DolWin5, in which the wind turbines are connected directly to the corresponding offshore platform via 66-kv three-phase power cables. This dispenses with, among other things, the transformer stations otherwise required in wind farms. With this direct connection, BorWin5 represents the new generation of cost-efficient offshore connections. Moreover, with BorWin5’s smart platform concept, the TSO is advancing standardisation further by installing only such technology on offshore platforms as is absolutely necessary on the offshore side.

Tim Meyerjürgens, COO of TenneT, emphasises the company’s continuous cost reduction in the construction of offshore grid connection systems – a highly significant aspect for the success of the energy transition – and the specific cost efficiency of BorWin5: “Compared to the predecessor project DolWin5, we were again able to achieve a significant cost reduction for the converter stations. One reason is that for BorWin5 the smart platform concept is being used for the first time. This not only keeps the costs for the platform construction manageable, but also allows us to extend the intervals for maintenance and servicing to once a year.”

TenneT awarded contracts for the on- and offshore converter stations as well as the underground and submarine cables for BorWin5 (picture shows the preparatory horizontal drilling for BorWin5 on Norderney in 2019)

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