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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TenneT records 21% increase in offshore transmission

28.07.2020

In the first half of 2020, the wind energy transmitted from the North Sea ashore by the Dutch-German transmission system operator (TSO) TenneT rose to 11.51TWh. This represents an increase of 21.1% compared with the 9.51TWh in the first half of 2019, bringing the North Sea’s share of total wind power generation in Germany to 15.6%. The maximum feed-in volume from offshore wind farms in the German North Sea was 6,035MW on 2 January 2020. By 30 June, the generation capacity of the German North Sea wind farms reached 6,679MW, a volume which is exceeded by TenneT’s offshore transmission capacity of 7,132MW. This amount, which is higher than the German government’s 2020 target (6.5GW for the North and Baltic Seas combined), is currently being achieved with twelve German offshore grid connections.

Tim Meyerjürgens, COO of the TSCNET shareholder, comments on the impressive figures: „The expansion and integration of offshore wind energy is of central importance for the European energy transition.” And offshore development is also keeping pace in the Dutch market: “With Borssele alpha and – from mid-August – Borssele beta, we have now also successfully completed the first two offshore connections in the Dutch North Sea.” TenneT promotes capacity expansion with technical innovations and, according to Meyerjürgens, wants to remain a driving force in the offshore sector: “Ever since TenneT set the standard for plastic-insulated DC cables at 320kV in the offshore sector around ten years ago, we have been defining a new global benchmark for the future with our 525kV DC subsea cable system and its transmission capacity of two GW.”

The 525kV development programme should lead to a standardised cable system that the TSO can employ by 2030 for the three German North Sea projects BalWin1, BalWin2, BalWin3 and the two Dutch projects IJmuiden Ver alpha and beta as well as in potential further projects of equal power and voltage. TenneT is expecting lower costs, greater security of supply and less impact on the environment. These efforts require considerable investment: “We have an investment programme of around €20bn earmarked for connecting offshore wind energy in the Netherlands and Germany by 2030,” explains Meyerjürgens. Important in this context are also hydrogen and hybrid initiatives. The North Sea Wind Power Hubs proposed by TenneT explicitly include power to gas concepts. Furthermore, in June, TenneT proposed to the EU and the Dutch and German governments an integrated energy system approach for the international offshore development.

TenneT increased its transmission of offshore wind energy by 21% in the first half of 2020 (picture: TenneT)

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TenneT develops 525kV HVDC offshore cable system

20.04.2020

In just 10 years, 40% of the Dutch electricity demand will be covered by offshore wind power. Furthermore, the Dutch-German transmission system operator (TSO) TenneT will increase the German offshore grid connection capacity to 17GW by 2030. To meet these high ambitions, the TSCNET shareholder expands its current connection plans and additionally intends to implement a total of five 2GW offshore connections in the Dutch IJmuiden Ver wind energy area and in the German LanWin and BalWin areas. However, since such 2GW offshore grid connections do not yet exist, innovative project development is necessary.

The integration of 2GW offshore grid connections into the onshore grid requires a suitable certified cable system that operates at a voltage level of 525kV DC using extruded insulation types. TenneT has contracted a total of eight cable suppliers to develop these “next-level” submarine cables for the intended high-performance offshore connections. An extruded 525kV high voltage direct current (HVDC) cable system with a 2GW output is currently not implemented in any project worldwide and would thus set a new standard for the connection of offshore wind farms.

The new cable system is expected to reduce manufacturing and installation costs for the entire connection concept, including the HVDC offshore and onshore transformer stations. A reduction in dredging costs is also anticipated, as all cables can be laid in a single trench. Moreover, fewer offshore platforms and shore stations are required, resulting in lower emissions and environmental impact. The adoption of a 525kV 2GW grid concept is a logical step for TenneT after the installation of eight standard AC connections in the Netherlands. The TSO can already draw on extensive experience with DC projects in Germany.

TenneT has contracted eight cable suppliers to develop a 525kV HVDC offshore cable system with a 2GW capacity (exemplary picture of Riffgat cables: TenneT)

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BorWin3 operation handed over to TenneT

14.02.2020

The offshore grid connection BorWin3 in the German Bight near the island of Borkum has been operational since August 2019. The twelfth offshore grid connection project of TSCNET shareholder TenneT, the Dutch-German transmission system operator (TSO), extends TenneT’s transmission capacity for offshore wind farms in the German North Sea by a further 900MW, so that the total capacity already amounts to 7.132GW – and since the German government’s expansion targets for wind energy in the North Sea by 2020 are only 6.5GW, the TSO has clearly exceeded them.

After several weeks of trial operation, BorWin3 has now been handed over to TenneT by the general contractors. The consortium of Siemens and Petrofac was responsible for the construction, transport, installation and commissioning of the two BorWin3 converters (offshore and onshore). The transfer of operations represents a further major contribution to the energy transition in Germany and Europe.

At the same time, TenneT is pursuing ambitious goals for its Dutch offshore projects. The TSO is planning on a large scale, as the Dutch government has set a target in its “Offshore Wind Roadmap 2030” to reach a cumulative offshore wind capacity of 11.5GW by 2030, so that 40% of the Dutch electricity demand will then come from offshore wind farms. In the IJmuiden Ver wind energy area, off the coast of the region of North Holland, the company intends to implement two 2GW offshore grid connections to complement the eight 0.7GW AC grid connections already planned in the Dutch North Sea. As there is currently no 2GW grid connection, a new platform design and a high-voltage direct current (HVDC) transmission system that enables increased power transmission are required.

Furthermore, given the long distance to the coast and the size of the IJmuiden Ver wind energy area, a 2GW HVDC solution based on 525kV seems to be the most economically solution. It requires only one cable system per 2GW, which limits the impact on the environment and surroundings. The technology is by no means fundamentally new to TenneT. The TSO can draw on its extensive HVDC experience with offshore grid connections in Germany and with interconnectors. TenneT also uses the 525kV level for NordLink, the new offshore connection between Germany and Norway.

To implement such an innovative DC system, TenneT has initiated the design phase with five HVDC suppliers based on an innovation partnership. These suppliers will develop the advanced 2GW-525kV HVDC solution based on the criteria defined by the company and the technical capabilities of the partners.

The operation of BorWin3 was handed over to TenneT (picture of the offshore converter platform BorWin gamma: TenneT)

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Construction start of DolWin 6 converter station

24.10.2019

The so-called DolWin wind farm cluster in the southwestern part of the German Bight is an important component of Germany’s future regenerative energy supply. TSCNET shareholder TenneT, the Dutch-German transmission system operator (TSO), is responsible for transferring the DolWin energy ashore. The DolWin1 and 2 onshore connections are in operation since 2015 and 2016 respectively, and DolWin 3 is ready for feed-in since September 2018. The other ongoing projects, DolWin 5 and 6, are also making good progress.

DolWin6 is a 900MW DC connection with a length of 90km. The associated offshore platform to convert the three-phase current generated by the wind farms into DC is DolWin kappa. Half of the 90km distance is covered by submarine cables and the other half by underground cables to transport the electricity from the landing site in Hilgenriedersiel to the TenneT facilities in Emden in the Lower Saxony region of East Frisia.

On the grounds of the Emden/Ost substation, the TSO is building a converter station and a transformer station to convert the DC back into three-phase current and feed it into the onshore grid. The first construction phase of the DolWin6 onshore converter station has now begun with the foundation work. In the next 6 months, 1000 piles with a length of up to 24 meters will be drilled into the ground to create a stable foundation for the station.

TenneT begins construction of the DolWin6 onshore converter station (pictures: TenneT)

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BorWin3 in operation

12.08.2019

The offshore grid connection BorWin3 operated by TSCNET shareholder TenneT in the German Bight is ready for feed-in since early August. This means that the total transmission capacity for offshore wind farms in the German North Sea is already 7.132GW. The Dutch-German transmission system operator (TSO) has thus not only met the German government’s expansion targets for sustainable North Sea wind power – 6.5GW by 2020 – but has significantly exceeded them.

BorWin3, TenneT’s twelfth offshore grid connection project, brings a further 900MW capacity. After BorWin1 and BorWin2, it is the third connection that the TSO has implemented near the East Frisian island of Borkum using DC technology. The corresponding converter and transformer station were built at TenneT’s Emden/Ost site to feed the green energy into the onshore extra-high voltage grid. BorWin3 bridges a total distance of 160km. The submarine cable is 130km long and the last section ashore to Emden/Ost is completed by underground cabling.

The TSO can be satisfied with its own offshore progress, but TenneT Managing Director Tim Meyerjürgens calls for further efforts, as the current rate of offshore wind expansion in Europe is not sufficient to achieve the goals of the Paris Climate Agreement. “An accelerated, large-scale and internationally coordinated expansion is necessary,” explains Meyerjürgens. In this context, TenneT has just presented a feasibility study of the North Sea Wind Power Hub concept for the implementation of wind power distribution hubs in the North Sea. Meyerjürgens points out that with an internationally coordinated approach the connection and integration of large offshore wind energy capacities could be much more effective and cost-efficient than with continued individual national planning.

In early August, the offshore grid connection BorWin3 of TenneT was put into operation (picture of the offshore converter platform BorWin gamma: TenneT)

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66kV technology reduces offshore connection costs

08.05.2019

In future offshore projects, TSCNET shareholder TenneT will continue to reduce grid connection costs through standardisation and innovative technology. For the DolWin5 offshore grid connection in the so-called DolWin cluster in the south-western part of the German Bight, the Dutch-German transmission system operator (TSO) has contracted a consortium consisting of Aibel and Keppel FELS with ABB as subcontractor with the design, engineering, procurement, construction, installation and commissioning of a 900MW offshore HVDC converter platform and an onshore converter station.

The outstanding feature of the DolWin5 project is the innovative connection concept. The innovative 66kV technology from TenneT, which will be deployed, represents a new generation of low-cost offshore grid connections. The wind turbines will be directly connected to the offshore platform without the need for separate substations for the wind turbines. This direct connection not only omits any further substations but also the 155kV three-phase power cables for linking the wind farm to the offshore platform. Instead, 66kV three-phase cables will be used.

“With DolWin5 we open a new chapter in offshore grid connection technology: For the first time, the wind turbines are directly connected to our offshore platform,” comments TenneT COO Tim Meyerjürgens and adds: “This innovative technology results in an enormous cost reduction. The new direct connection will save around €200m in macroeconomic terms.”

TenneT opts for the innovative 66kV three-phase technology for future offshore connections (Picture: TenneT)

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Record-setting offshore connection

09.04.2019

The IJmuiden Ver offshore wind farm project in the Dutch sector of the North Sea will be equipped with two onshore connections from 2024 to 2030. TSCNET shareholder TenneT, the Dutch-German transmission system operator (TSO), has announced to link the 6.1GW of the new offshore wind farms to the Dutch high-voltage grid via two 525kV DC cables with a capacity of 2GW – this will be the highest in the world. As a result of the increased capacity, only two instead of six cables will be required, resulting in lower costs, as well as less space requirements and environmental impact.

A total of four converter stations are required for the DC transmission, which prevents transport losses: two offshore converter platforms for converting the wind-generated AC into DC and two onshore converters for the reconversion. The 2GW connections are possible due to TenneT’s unique experience with HVDC grid connections in Germany, where TenneT will connect offshore wind farms with DC technology on a large scale. The TSO also uses the 525kV high voltage level for NordLink, the new international connection between Germany and Norway, as well as for the German onshore projects SuedLink and SuedOstlink.

TenneT has ambitious offshore plans, since the TSO has been commissioned by the Dutch government to connect a total of 9.6GW offshore capacity, of which 5.6GW will be realised with AC connections and 4GW with innovative DC connections. Together with the offshore wind farms already in operation, the offshore wind energy capacity is expected to reach 10.6GW in the Netherlands in 2030. Because of the considerable total capacity of IJmuiden Ver, the associated onshore connection is a core component of TenneT’s offshore grid development in the Netherlands.

Manon van Beek, CEO of TenneT, comments on the IJmuiden Ver project: “We are making an important contribution to accelerating the energy transition. Based on our experience with innovative technology in Germany, we can now help to realise the Dutch ambitions for the development of offshore wind energy with fewer cables, fewer platforms and less spatial impact and nuisance to the environment, both at sea and on land.”

TenneT connects Dutch offshore wind farm with a record capacity of 2GW (picture: TenneT , artist’s impression)

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Increase in North Sea capacities

11.01.2019

In terms of the “wind harvest” in the German control area of TSCNET shareholder TenneT, 2018 has been yet another record-breaking year. The result in 2018 exceeded the previous year’s figure by 4.9 percent. The wind energy transmitted from the North Sea by the Dutch-German transmission system operator (TSO) amounted to 16.75TWh in 2018 – a new record. This was made possible by a total transmission capacity of 6,232MW provided by altogether eleven offshore connection systems, which have by now been connected to the onshore grid by TenneT.

That is more than in line with the German political targets. “With this, TenneT has now almost entirely achieved the federal government’s expansion goal of having 6,500MW of offshore wind capacity by 2020,” comments TenneT Managing Director Wilfried Breuer. And what’s more: “Already this year, TenneT will exceed this goal since the completion of BorWin3 in the course of 2019 will put a total of 7,132MW of transmission capacity into operation in the North Sea alone.”

In addition to the company’s infrastructural efforts, TenneT pursues numerous innovative technological approaches. A current example in the offshore sector is the planned 66kV technology, which will be used for the future TenneT offshore connections DolWin5 and BorWin5. 66kV technology can reduce investment and operational costs by millions as it supersedes offshore transformer platforms and significantly reduces the amount of cables required to connect individual turbine systems.

TenneT has increased its offshore transmission capacity from the German North Sea (picture: TenneT)

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Significant increase in German offshore capacity

15.01.2018

In the range of its German control area, TSCNET shareholder TenneT, the Dutch-German transmission system operator (TSO), has increased the offshore capacity to 5,332MW in 2017. Ten connection projects for the transmission of offshore wind energy to the onshore grid have already been completed, while two further connections are expected to be operational in 2019. Since four more grid connections are planned by 2025, the transmission capacity in the German North Sea is expected to increase to over 10,000MW.

“TenneT already now meets more than 82 percent of the German Federal Government’s expansion target, which envisages offshore wind capacity of 6,500MW by 2020,” says Lex Hartman, member of the TenneT executive board. The satisfactory offshore development is accompanied by further impressive numbers: The 2017 North Sea “wind harvest” exceeded the previous year by 47 percent, equating to a remarkable 15.9 percent share of total wind power generation in Germany. “The strong growth in the North Sea ‘wind harvest’ indicates that offshore wind power has become a major energy factor with high reliability,” adds Mr Hartman.

> See TenneT press release, in German (html)

Picture: TenneT (topside of SylWin1 grid connection)

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