Improving biodiversity for submarine cabling

15.10.2020

Looking at the big picture – the energy transition and the achievement of the European climate targets – there is no alternative to expanding offshore capacity for the generation and transmission of North Sea wind power. For that reason, both the Dutch and German governments have set ambitious targets for offshore expansion, which the Dutch-German transmission system operator (TSO) TenneT is gradually implementing and has even exceeded for its German North Sea control area. In the individual case, however, each offshore construction and operational measure obviously has an impact on the valuable North Sea and Wadden Sea ecosystems. As TenneT strives to apply and monitor nature-friendly solutions in all of its offshore grid projects, the TSO is now conducting pilot tests with stone coverings of submarine cable intersections.

When the TSCNET shareholder lays submarine cables, e.g. currently for the high-voltage connection of the Hollandse Kust (zuid) wind region, the cables sometimes cross with existing oil and gas pipelines. In such cases, the cables protrude above the seabed and are usually covered with a layer of granite to protect them. To replace granite with alternative solutions that promote biodiversity, TenneT has launched a pilot project in collaboration with the offshore specialist company Van Oord. In this project, different types of stones are deposited at cable crossings to investigate which of these stimulates biodiversity best. In total, the pilot involves twelve locations in the North Sea. In the case of the first six, recently laid submarine cables already cross existing oil and gas pipelines. Another six intersections will follow during the construction of the Hollandse Kust (Zuid) connection in 2021.

On 14 October, the different stones were loaded onto Van Oord’s special vessel to be placed at the cable intersections in the coming weeks. Among them are small calciferous stones from a marble quarry, which are placed at three of the six cable intersections. Comparison with the other three intersections without calciferous stones will allow to assess the difference in the type of marine life developing at these intersections. “Our expectation is that the calciferous stones will ensure that various benthic species will find it easier to nest here and that a different habitat will emerge at these sites. Over the years, ‛artificial reefs’ can emerge at these sites in the North Sea, where plants and small creatures can settle,” explains Saskia Jaarsma, Head Offshore Developments and Large Projects Offshore at TenneT.

TenneT has launched a pilot project to promote biodiversity at submarine cable intersections (picture: Van Oord)

Linkup
> See TenneT press release (html)

See article on single page

Substantial EU funding for Harmony Link

02.10.2020

The Connecting Europe Facility (CEF) is an important financial instrument of the EU to support targeted infrastructure investments at European level. On 1 October 2020, the coordination committee of the CEF decided to allocate €719.7m for investment in electricity transmission infrastructure in Poland, Lithuania, Latvia, and Estonia. The granting follows an application for funding submitted at the end of May this year by the national transmission system operators (TSOs) of the three Baltic States and by PSE, the Polish TSCNET shareholder.

Harmony Link, which is to be the second interconnector between Poland and Lithuania, particularly benefits: €493m will be directly allocated to the project. Further funding is intended for the upgrading of infrastructure required for the integration of Harmony Link and for the installation of synchronous compensators in the Baltic States.

The first Polish-Lithuanian interconnector is LitPol link, an overhead line connecting the PSE substation in Elk and the Lithuanian Alytus substation, which has been in operation since 2016. Harmony Link is implemented in a different technical way, as a high voltage direct current (HVDC) submarine cable bypassing the Curonian Lagoon and the Gdańsk Bay. The new Polish-Lithuanian interconnector is crucial to enable the synchronisation of the Baltic electricity area with the Continental European (CE) area – an important objective in the framework of the European Energy Union to create a common European electricity market. It will also support regional and supra-regional supply security.

The EU is funding the Polish and Baltic electricity infrastructure with €719.7m through the CEF Energy programme (picture of Gdańsk Bay seen from Gdynia: NAC on Wikimedia Commons, CC BY-SA 4.0)

Linkup
> See PSE press release (html)

See article on single page

Deep Dig-It starts work for Hollandse Kust (zuid) grid

24.09.2020

Hollandse Kust (zuid), an offshore wind area in the Dutch North Sea, is located a good 20 kilometres off the coast of the Dutch province of Zuid-Holland. The Dutch-German transmission system operator (TSO) TenneT is installing the related offshore grid to connect the new offshore wind farms in the area via two offshore platforms and submarine cables to the onshore high-voltage substation that is being built in the Maasvlakte industrial and port area. The jacket for the first of these two offshore platforms has recently been installed and the offshore connection project is now making further progress with the start of the laying of the submarine cables on 22 September.

Four 220kV AC cables with a total length of 42 kilometres each are to be installed in the seabed, of which the first two to the Alpha platform will be laid this year. The other two to the Beta platform will follow in 2021. First, the two cables were brought ashore to the planned Maasvlakte substation via direct drilling. Thereupon the TSCNET shareholder started the marine installation, with the first ten kilometres of the route from the coast at Maasvlakte being extremely challenging. Over this distance, the cables cross the entrance to the port of Rotterdam – Europe’s busiest cargo port – and thus need to be buried more than 5.5 metres deep. For this purpose, the contracted specialist company Van Oord uses its Deep Dig-It trencher, an enormous remote-controlled trencher.

The Deep Dig-It is one of the largest and most powerful devices in its class. The trencher weighs 125 tonnes, is more than 17 metres long, well over 8 metres high, and 11 metres wide. With its enormous power it can bury cables deeply even in very hard ground. The trencher is controlled from an offshore installation vessel equipped with a crane to lower and lift out the high-performance machine. The Deep Dig-It moves unmanned over the seabed and creates a deep trench for the cables by liquefying the seabed. Simultaneously, the Deep Dig-It inserts the cables into the trench and seals the seabed afterwards. With work progressing well, Tennet expects the 1,400MW Hollandse Kust (zuid) grid connection to be completed in 2022.

TenneT has started the laying of submarine cables for the Hollandse Kust (zuid) grid connection (picture: Van Oord)

Linkup
> See TenneT press release (html)
> Watch TenneT video of the Deep Dig-It at work (YouTube)

See article on single page

Jacket for Hollandse Kust (zuid) Alpha platform installed

08.09.2020

The offshore wind area Hollandse Kust (zuid) is located 22 kilometres off the coast of the Dutch province of Zuid-Holland. The Dutch-German transmission system operator (TSO) TenneT will connect the wind farms in this area to the onshore substation in the industrial and port area of Maasvlakte via two offshore platforms – Alpha and Beta – and submarine cables. The jacket for the Hollandse Kust (zuid) Alpha platform was transported to the operation site by a heavy-duty vessel on 5 September and successfully installed on the seabed. The Alpha jacket is 29 meters long, 20 meters wide, 46 meters high and weighs 3200 tonnes. It will be further installed in the coming days.

The two 220kv submarine cables will be connected to the jacket over the next few months. In 2021, the platform top side will be placed on the jacket. The Hollandse Kust (zuid) Alpha platform is expected to be operational by the end of 2021. The projects in this new wind area are part of the large-scale offshore expansion programme of TenneT. By the end of 2023, the TSCNET shareholder will have installed 3.5GW of offshore grid connections in the Netherlands, of which the first 1.4GW have already been achieved with Borssele Alpha and Beta. The connection to follow Hollandse Kust (south) will be Hollandse Kust (nord). For all the wind farms in these two areas, TenneT will deploy five identical 700MW transformer platforms and identical 220kV cable connections. “Such standardisation enables TenneT to complete these projects more efficiently, more quickly, and more economically,” explains TenneT COO Tim Meyerjürgens.

The Dutch national roadmap for offshore development provides for an additional 6.1GW of offshore wind farms in the wind energy areas Hollandse Kust (West), Ten Noorden van de Waddeneilanden, and IJmuiden Ver from 2024 to the end of 2030. For the first two areas, TenneT will again use standardised 700MW offshore platforms. The efficient connection of IJmuiden Ver, which is located further out in the North Sea, partly requires other technologies based on DC instead of AC. IJmuiden Ver will have two offshore transformer platforms with a capacity of 2GW each, which is unique in the offshore wind industry.

TenneT has installed the jacket for the Hollandse Kust (zuid) Alpha platform (picture: TenneT)

Linkup
> See TenneT press release (html)

See article on single page

TenneT commisions “green” substation

04.09.2020

In recent years, the seaport of Eemshaven in the province of Groningen in the north of the Netherlands has become more and more important for the Dutch energy transition. Eemshaven has taken on the role of an energy port: with power plants, sustainable generation, connections to offshore wind farms, and submarine cable interconnectors to Norway and Denmark. The Dutch-German transmission system operator (TSO) TenneT – together with regional distribution system operator (DSO) Enexis Netbeheer – now has commissioned the new high-voltage substation Eemshaven as the first substation entirely built for the suply of wind and solar energy.

The station was built as part of the grid reinforcement for the growing amount of sustainably generated energy in the north of the Netherlands which requires an increase in transmission capacity. Other measures of the TSCNET shareholder include a 380kV connection between the Eemshaven (Oudeschip) high-voltage substation and Vierverlaten near Groningen as well as the extension of the Vierverlaten substation. This new 380kV “power highway” will replace the existing 220kV line. Until it is put into operation – scheduled for 2023 – TenneT will commission a provisional 380kV substation in Eemshaven (Oostpolder) in October 2020.

TenneT has put into operation the new substation Eemshaven for the supply of green electricity (picture: TenneT)

Linkup
> See TenneT press release, in Dutch (html)

See article on single page

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)

Linkup
> See TenneT press release (html)

See article on single page

Foundation laid for DolWin6 converter

28.05.2020

With a dozen operating offshore connection systems for wind farms in the German North Sea totalling a transmission capacity of 7.132GW, the Dutch-German transmission system operator (TSO) TenneT has already in 2019 exceeded the German government’s expansion target for offshore wind energy capacity for 2020 by more than half a million GW. A further 900MW will be provided by DolWin6, like the predecessor projects DolWin3 and BorWin3 a high-voltage direct current (HVDC) connection. The DolWin kappa offshore platform in the Wadden Sea near the island of Norderney will convert the three-phase wind current into DC for transmission via a 45 kilometre submarine cable to the East Frisian mainland and from the landing point via an underground cable, also around 45 kilometres long, to the TenneT site in Emden/East.

Here, the TSCNET shareholder is constructing the DolWin6 onshore converter station and a substation on 23,500m² to reconvert the DC into three-phase current for feeding into the onshore extra-high voltage grid. A significant milestone for DolWin6 was reached on 27 May: The laying of the foundation at the converter construction site was celebrated in Emden/East by embedding a time capsule with coins, a regional daily newspaper, and construction plans into the foundation stone. Due to the Covid-19 pandemic, the event was only celebrated with the most important project managers from TenneT and the plant constructor Siemens.

Concrete preparations for DolWin6 began in the summer of 2017 and 2018 with horizontal drilling on Norderney. In September 2019, the foundation work commenced in Emden/East. Work on the DolWin kappa offshore platform at a dockyard in Cádiz/Andalusia also started in mid-2019 and the DolWin6 cable laying will follow from summer this year. The completion of the HVDC offshore connection is scheduled for 2023.

TenneT celebrated the laying of the foundation stone for the DolWin6 converter in Emden/East (picture: TenneT)

Linkup
> See TenneT press release, in German (html)

See article on single page

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)

Linkup
> See TenneT press release (html)

See article on single page

Deep Dig-It trencher at work for TenneT

09.03.2020

The Hollandse Kust (South) offshore wind area in the Dutch North Sea is located 22 kilometres off the coast of the Dutch province of Zuid-Holland. TSCNET shareholder TenneT is responsible for connecting the wind farms under construction there via two corresponding offshore platforms to the onshore high-voltage substation in the industry and port area of Maasvlakte, from where the green electricity is transmitted further to the Randstad 380kV South Ring power line in the Dutch Randstad region, the most densely populated area in Europe, and further.

But there is a major challenge to be met by the Dutch-German transmission system operator (TSO): On the first ten kilometres of the offshore route, the four submarine cables to be laid are crossing the entrance to Europe’s busiest cargo port, the port of Rotterdam. To pass through the busy Rotterdam-Maasmond shipping lane, the cables here must be buried more than 5 metres deep into the seabed. For this specific job, the Dutch maritime contracting company Van Oord designed and built the Deep Dig-It trencher, a gigantic remote-controlled trencher.

Last Friday, final tests were carried out in the Aleksiahaven of Maasvlakte in preparation for the actual laying of the submarine cables in July. The innovative device is a so-called Tracked Remotely Operated Vehicle, which drives unmanned over the seabed, creates a deep trench for the cables, inserts the cables and closes the trench again. The Deep Dig-It is the largest and most powerful machine in its class. The trencher weighs 125 tonnes, is more than 17 metres long, well over 8 metres high and 11 metres wide. This makes it possible to bury cables in very hard ground, while the burial depth that can be achieved with the Deep Dig-It is well over 5 metres.

TenneT employs the powerful Deep Dig-It trencher to connect the Hollandse Kust (South) wind farms to the onshore grid (picture: Van Oord nv)

Linkup
> See TenneT press release (html)

See article on single page

COBRAcable proves to be a great success

06.03.2020

It is now half a year since TSCNET customer Energinet, the transmission system operator (TSO) from Denmark, and TSCNET shareholder TenneT, the Dutch-German TSO, made COBRAcable available to the market. The high-voltage DC cable with a length of about 325km and a capacity of 700MW is the first direct connection between the electricity markets of Denmark and the Netherlands. The basic idea behind COBRAcable is to compensate for the volatility of wind power. Consequently, the Netherlands imports electricity via the cable on days with large Danish wind power generation, while on days with little wind in Denmark the electricity is transported in the opposite direction.

This works perfectly, as the interconnector’s transmission data from the first six-month period prove: In total, Denmark has imported almost 700GWh via the COBRAcable and the Netherlands almost 1,400GWh. On average, COBRAcable was operated at full capacity 79% of the time during the last half year. The impressive traffic on this binational connection proves its adequacy through its operation. The new interconnector therefore substantially contributes to the energy transition by exchanging volatile renewable energy across borders and additionally creates a trading profit on the spot market for electricity – a multiple benefit for nature, society and the companies involved.

The transmission data from the COBRAcable of Energinet and TenneT confirm a high level of traffic on the line (picture: screenshot taken from Energinet-video “Constructing the green COBRAcable”, Vimeo)

Linkup
> See Energinet press release (html)

See article on single page