Connecting wind energy THE OFFSHORE GRID IN THE NETHERLANDS

Connecting wind energy THE OFFSHORE GRID IN THE NETHERLANDS

Bringing wind power from sea to land 3 As the developer and operator of the high-voltage grid in the Netherlands, on land and at sea, TenneT will realise offshore grid connections with a capacity of at least 3,500 MW by 2023, in a standardised concept of 700 MW per connection. The roll-out of the offshore grid will go hand in hand with the development of the wind farms. DEVELOPMENT of the offshore grid In the Netherlands, offshore wind power accounts for an ever-greater share of the energy supply, and will continue to grow in the near future. By 2023 a significant amount of the Netherlands electricity demand will be generated by offshore wind, located in zones in the North sea. As the developer and operator of the high-voltage grid, on land and at sea, TenneT has the responsibility to connect this new offshore energy and transport it safely and reliable to shore. As we look ahead to 2023, the Dutch government has set out a roadmap for bringing more offshore wind energy to the mainland the Routekaart Windenergie op zee. This sets out a schedule for connecting 3,500 MW of offshore wind power, with a timetable of when each wind energy zone will be operational. These zones are Borssele, Hollandse Kust (south) and Hollandse Kust (north), respectively. The roadmap has been developed in consultation with stakeholders. The Dutch offshore wind programme until 2023 will provide a total capacity of at least 3,500 megawatts (MW), on top of the 1,000 MW that is already operational. Bringing this much power from sea to land will make an important contribution to the Dutch government s renewable energy targets, as set out in the National Energy Agreement. As TenneT is the offshore grid developer for the Netherlands and also for the German part of the North Sea, we have built up significant experience in connecting offshore wind energy and integrating it into the electricity grid, connecting over 5,300 MW of offshore wind power and more than 2,800 MW under construction. And by 2025 TenneT will provide over 10 GW transmission capacity in the German North Sea. When developing the Dutch offshore grid, we went through an intensive consultation process that brought together experts from TenneT and leading (inter)national players in the wind energy sector. Together, we explored the technology, planning, design and construction of the offshore grid and, using all of our combined expertise, devised the optimum solution for bringing this Dutch North Sea wind power to shore. OFFSHORE WIND THREE PHASE DEVELOPMENT Short Term (to 2023) Currently 3,5 GW* under development (near shore) Medium Term (to 2030) Further expansion of 7-10 GW* in wind energy areas, also further offshore preparing of international cooperation Long Term (to 2050) Future expansion of 100-200 GW* via wind energy islands in the North Sea international cooperation necessary * gigawatt, or 1,000 megawatt (MW) 4,500 MW Electricity from the offshore grid is enough to power nearly half of all Dutch households. GRID OPERATOR The Dutch government appointed TenneT as the offshore grid operator in 2016. ASSURED OF ENERGY TenneT safely and securely connects the energy from the offshore wind farms to the onshore high-voltage grid. TenneT is developing five new offshore grid connections, connecting the offshore wind farms and transporting the electricity to the onshore electricity grid and consumers. These will be constructed in stages over the next few years. Borssele Beta Borssele Alpha Hollandse Kust (south) Alpha Hollandse Kust (north) Hollandse Kust (south) Beta

Bringing wind power from sea to land 5 The offshore grid concept consists of standardised grid connections to wind farms built in the three wind energy zones designated by the Dutch government. They will collect the energy generated offshore and transport this to the onshore electricity grid. Offshore grid CONCEPT The platform is one of the main parts of the offshore grid. The energy generated in the wind farms is transported to an offshore platform owned by TenneT and then, via the two 220 kv AC cables, to an onshore high-voltage station. The size of the platform is optimized at 700 MW. Multiple wind farms can be connected on a 700-MW platform, which helps reduce the social cost and environmental impact. The offshore grid is compact, reliable and future-proof. The offshore grid helps to reduce the costs of offshore wind power and reduces the impact on the environment. AC 700 MW substation high-voltage grid transformer station dunes 66 kv cables sea cable onshore cable high-voltage station 66 kv cable 220 kv cable 380 kv cable offshore wind farm TenneT s offshore grid onshore transport grid 220 kv CABLES 66 kv CONNECTION VOLTAGE The platform of the offshore grid will be the first in the world to have a connection voltage of 66 kilovolt (kv) instead of 33 kv. OFFSHORE PLATFORM The platform is the heart of the grid connection. It transforms the voltage level from 66 kv to 220 kv. It consists of a steel topside and jacket that are built separately. The 220-kV offshore cable has a diameter of approximately 280 mm and consists of three single-phase conductors, and two (or three) optical fiber cables, bound together and covered with steel wires. TRANSFORMER STATION The onshore transformer station will raise the voltage level from 220 kv to 380 kv in order to directly connect the wind energy to the onshore high-voltage grid.

Well THOUGHT OUT TenneT has applied a lean and mean approach. This will ensure lower costs for development, construction and maintenance of the Dutch offshore grid concept. OFFSHORE CABLE The excavated trench carrying the four* offshore cables is 1,600 metres wide: 200 meters between the cables, with a safety zone of 500 meters on either side. ONSHORE CABLE Zone for the four* onshore cable systems after being laid: 19.5 meters, including safety zones. Each onshore cable system consists of three separate single-phase cables. They can also be laid in a triangular shape. 500 Corridor of offshore cable 1,600 m. Cable system A1+A2 Corridor of onshore cable 19.5 m. Cable system B1+B2 200 200 200 Cable system A1 Cable system A2 Cable system B1 Cable system B2 25 50 50 500 50 50 500 50 50 500 50 50 25 500 The wind farms will be connected directly to TenneT s platform, requiring fewer offshore platforms. The connecting cables from the wind farms to the platforms have a supply voltage of 66 kv as opposed to 33 kv. As such, more capacity can be transported per cable, requiring fewer cables. The platform is not that far offshore and can be easily reached by boat, which means a helideck will not be needed. The platform is more compact because all of the spaces can be reached from the exterior. Availability of spare parts, thanks to a standardised approach. For instance, one spare transformer can boost the availability of all the offshore grid connections. * In the case of two offshore grid connections, Alpha and Beta, the four cables will be laid together. UNMANNED Cable transport Ships will transport the long and heavy three-phase cables on reels, out to sea and in some cases to near shore locations. These cable reels are not suitable for transport onshore due to their weight. Therefore TenneT will use three separate singlephase 220 kv cables for the onshore route to the connection with the transformer station. As a result, there will be six separate single-phase 220 kv cables laid per grid connection. Room for innovation TenneT is allowing the contractors to propose innovative technologies, where suitable. For instance, for building and laying the cable, TenneT will determine the installation requirements such as transport capacity, respective distances and excavation depth, while the contractor will determine the method of installation in the detailed design. Measuring and communication equipment on the platform The platforms will also be used as maritime information service points. This is of significant interest to various governmental and semigovernmental organisations that will benefit from a permanent measurement station in the North Sea. A range of sensors will be installed to provide essential information, such as data on wind speed, waves, shipping, and the migration of birds and bats. With this compact, reliable and future-proof concept, experts from the (inter)national wind energy sector, the Dutch government and TenneT will make an important contribution to cutting the costs of offshore wind power. DYNAMIC LOADING Because electricity generated by the wind varies, the load of the cables that transport the electricity must also vary. The cable can handle more than 350 MW for a temporary period of time: if the temperature of the cable doesn t get too high, the cable can, in certain circumstances, transport an additional and temporary 30 MW. TenneT will make this dynamic loading possible under certain conditions and will keep a close eye on the temperature of the cable. Thanks to this approach, the offshore wind farm developer will have the optionality to install an additional 30 MW of wind turbine capacity, i.e. overplanting. The platforms do not have to be permanently staffed. As such, they can be fitted out in a simple manner with fewer facilities. UNDERGROUND The cables will go underground to the onshore transformer station and to the connection point at the high-voltage station. LOW WEIGHT The weight of the topside of the platform is purposely low so that it can be placed using standard heavy-lift ships.

COBRAcable (Denemarken) NorNed (Noorwegen) Bringing wind power from sea to land 11 Offshore grid connections Eemshaven Oudeschip Eemshaven Oost Robbenplaat Eemshaven Converterstation Eemshaven Weiwerd COBRAcable (Denemarken) NorNed (Noorwegen) Bergum Vierverlaten Meeden Louwsmeer Zeyerveen IN THE NETHERLANDS AND GERMANY Hollandse Kust (noord) Alpha Ens Hessenweg Zwolle alpha ventus AC 66 km 62 MW Hagermarsch BorWin1 200 km 400 MW Diele BorWin2 200 km 800 MW Diele Eemshaven Oudeschip Eemshaven Oost Eemshaven Converterstation Eemshaven BorWin3 160 km 900 MW Emden/Ost DolWin1 165 km 800 MW Dörpen/West DolWin2 135 km 916 MW Dörpen/West Hengelo Robbenplaat Weiwerd TenneT has been designing, planning, building and operating grid connections for offshore wind farms in Germany since 2006. In the Netherlands, we were formally appointed as offshore grid developer in 2016. A few wind farms in Germany are located just off the coast. The majority of the wind farms are located further offshore and are therefore equipped with a direct current () connection. Wind farms that will be built in the Netherlands before 2023, will be at a shorter distance and will therefore be equipped with an alternating current (AC) connection, which is then more efficient. 1 Borssele Alpha AC 62 km 700 MW Borssele Commissioning in 2019 2 Borssele Beta AC 69 km 700 MW Borssele Commissioning in 2020 3 Hollandse Kust (south) Alpha AC 43 km 700 MW Maasvlakte Commissioning in 2021 4 Hollandse Kust (south) Beta AC 34 km 700 MW Maasvlakte Commissioning in 2022 Borssele Beta Borssele Alpha 5 Hollandse Kust (north) AC 700 MW cable route and landing location being investigated. Commissioning in 2023 Hollandse Kust (zuid) Alpha Hollandse Kust (zuid) Beta Maasvlakte Borssele Weert Maasbracht Gronau (Duitsland) Doetinchem Wesel (Duitsland) Rommerskirchen (Duitsland) Siersdorf (Duitsland) Hollandse Kust (north) Alpha Hollandse Kust (south) Alpha 3 Hollandse Kust (south) Beta 4 Maasvlakte 5 Bergum Ens Louwsmeer Vierverlaten Hessenweg Zwolle Zeyerveen DolWin3 160 km 900 MW Dörpen/West Doetinchem Hengelo Meeden Wesel (Duitsland) DolWin6 90 km 900 MW Emden/Ost Gronau (Duitsland) HelWin2 130 km 690 MW Büttel BorWin3 SylWin1 205 km 864 MW Büttel Riffgat AC 80 km 113 MW Emden/Borssum SylWin1 HelWin1 130 km 576 MW Büttel Nordergründe AC 32 km 111 MW Inhausen BorWin2 HelWin2 HelWin1 Borssele Beta 2 1 Borssele Alpha alpha ventus DolWin2 Borssele Weert Nordergründe Hagermarsch Büttel Wilster Maasbracht Rommerskirchen (Duitsland) Siersdorf (Duitsland) Emden/Ost Diele Dörpen West

Bringing wind power from sea to land 13 Challenging CIRCUMSTANCES If an open excavation is not an option, a horizontally powered drill could be a solution. The cable gradually arrives at the desired depth through the entry point. Where possible, cables are laid in an open excavation. A trench for the cables is dug, and then buried in autochthonous material. The offshore project teams are accustomed to working in challenging circumstances, even right from the preparation phase. In this case, the practical conditions and technical requirements of the project can complicate the choice of cable track and platform location considerably. For instance, the platforms should be easily accessible for maintenance ships, with no obstacles within a 500 m. radius and they should also be close to the wind farms, with cables kept as short as possible. Meanwhile, the power cables should not cross pre-existing installations, such as data cables or pipelines (or at least keep this overlap to a minimum). They should also avoid areas that are important for nature, shipping, archaeology, fishing or recreation. Unexploded ordnance on the seabed is another hazard: it is impossible to avoid all areas where there are explosives, so these obstacles need to be mapped out during the preparation process and removed if necessary. As TenneT explores possible routes for the grid connections, we consult with a wide range of stakeholders, including national and provincial governments, water boards, municipalities and NGOs. All stakeholders can have their say at different stages in the process. The final decision on the cable routes, landfalls and transformer stations will be made by the relevant Minister and laid down in a so called inpassingsplan. Once the cable route has been decided and the permits are in order, we can begin installing the offshore grid. That s when the offshore challenges start, not least dealing with weather conditions, which can have a major impact on the work. Preparing for and actually building an offshore grid is an intensive process. Being ready to start installing the platforms and cables, we may also face major challenges from the weather. COASTAL DEFENCES If offshore cables need to cross dunes or dykes, TenneT will consult Rijkswaterstaat or the water board about the most suitable technique. CABLE TRACK TenneT and the relevant Ministries are investigating possible alternatives for the track. SAFE TenneT is investing in regular safety training courses to be able to carry out our duties as safe and professional as possible.

Bringing wind power from sea to land 15 Electricity has to travel far and wide to reach households and businesses. While making this possible, TenneT takes measures to minimise the impact on nature and the environment, protecting the landscape and the biodiversity of the area. Considerate OF NATURE AND THE ENVIRONMENT PREVENTION Negative effects on the environment are prevented or limited where possible. ARTIFICIAL REEF Offshore platforms act as an artificial reef and increase biodiversity. ENVIRONMENTAL IMPACT The environmental impact of the alternative tracks is outlined in the MER. As such, taking care of nature and the environment is an integral part of our work to develop the offshore grid. For instance, there is a detailed study of the environmental effects of the alternative routes. They are outlined in an environmental impact report (known as MER in Dutch) and help determine the final route choice. Onshore work activities are done in such a way that breeding birds or other protected species of animal or plant are not disturbed. TenneT makes sure that any negative impact on the natural environment at sea is minimised. Wind farms and platforms can, however, also have a positive effect on the environment. Studies have shown that the biodiversity on the seabed increases near such structures as platforms and wind turbines. Many species of underwater animals were found, including fish such as cod, mackerel and ocean pout. TenneT takes measures to minimise the impact on nature and the environment.

Bringing wind power from sea to land 17 Generating more offshore wind power is one of the most important pillars of energy transition in Europe. The Dutch and German governments are not alone in wanting to increase the amount of offshore wind power over the coming years. What s more, other sources of renewable energy are also on the rise. OFFSHORE GRID IN THE FUTURE MIDTERM PLANS UNTIL 2030 In the mid-term until 2030, the Dutch government wants to be able to generate 7-10 GW more wind power than planned until 2023, also in wind energy zones located further offshore. TenneT will connect these offshore wind farms and link them to the onshore electricity grid. Efficiently connecting the wind energy zones further out in the North Sea, for example IJmuiden Ver, will require a different technical approach, using a direct current () connection instead of an alternating current (AC). Although complex and challenging, TenneT is devoting its time and expertise into developing connections for this zone at the lowest possible cost for society and the environment. One of the options we are exploring is combining some of these connections with an interconnector, i.e. an international electricity connection between countries. 2030 2050 Sun and wind form the basis for a sustainable and stable energy system. More sun is available from springtime, and more wind from the autumn. TenneT ensures that there is electricity for all users throughout the year, also at moments or places where the wind doesn t blow or the sun doesn t shine. COOPERATION ON THE NORTH SEA LONG TERM PLANS UNTIL 2050 To be able to access the required amount of generated energy in the mid and long term until 2050, it is important that we are able to exchange electricity with our neighbouring countries. Besides the named exchange of electricity via interconnec tors, Europe also requires a coordinated joint effort by national governments, regulators, the offshore (wind) industry, national grid operators, and nature and environmental organisations. TenneT has taken the initiative to come up with a shared European approach until 2050. This concept has the potential to provide renewable energy to 70-100 million European consumers by 2050. The concept utilises the North Sea as an important source and distribution centre of generated wind power that can be exchanged between the various neighbouring countries. These countries exchange the electricity via man-made islands connected to the mainland. In turn, new wind farms built near the islands can be connected to it.

TenneT is a leading European electricity transmission system operator (TSO) with its main activities in the Netherlands and Germany. With over 22,000 kilometres of high-voltage connections, we ensure a secure supply of electricity to 41 million end-users. We employ approximately 3,000 people, have a turnover of EUR 3.2 billion and an asset value totalling EUR 19 billion. TenneT is one of the biggest investors in national and international electricity grids on land and at sea. Our focus is on developing an integrated Northwest European energy market and enabling the energy transition. TenneT makes every effort to meet the needs of society by being responsible, engaged and connected. Taking power further TenneT TSO B.V. Mariëndaal Centre of Excellence, Utrechtseweg 310, 6812 AR Arnhem, The Netherlands +31 (0)26 373 11 11, communicatie@tennet.eu FSC logo https://www.tennet.eu/netopzee November 2017