Energy islands as nodes between offshore wind farms


Energy islands as nodes between offshore wind farms

In the Danish Esbjerg – logistics hub in the wind energy sector – Belgium, the Netherlands, Germany and Denmark in mid-May 2022 have agreed to work more closely on large-scale offshore wind. By 2030, the total capacity for offshore wind is to be increased to 65 gigawatts, a quadrupling of the current capacity. A crucial part of the plans are artificial energies, from which sustainable electricity and green hydrogen are brought ashore.

Author: Tseard Licorice

The basis for the agreement was laid last year, when our southern neighbors and Denmark agreed to lay the Triton power cable, so named after the Greek sea god, between the two countries. It must be operational by 2030. At around six hundred kilometers, Triton will be one of the longest submarine cables in the EU, connecting our southern neighbors with Denmark. Denmark has little industry, but it has a surplus of sustainable electricity thanks to wind farms on land and at sea. For Belgium, it is just the opposite: a short coastline, significantly heavier industry (think of Antwerp and the Brussels region) and a lack of sustainable electricity. If this proves to be economically feasible, Triton will be linked to an artificial energy island about 40 kilometers off the coast of Ostend.

In recent years, large wind farms in the North Sea have emerged at an increasing pace. For example, no fewer than five wind farms with a total of more than 2.2 gigawatts have come into operation in our southern neighbors since 2019, accounting for about seven percent of Belgian electricity consumption.

With more than 2.4 GW, the Netherlands not only has more capacity, but also much greater potential on our part of the continental shelf. In addition to the existing wind farms off the coast of the Netherlands (North Sea Wind, Luchterduinen and Princess Amalia), the newer ones off the coast of Zealand (the five wind farms in Borssele) and those north of the Wadden Sea (Gemini), plans are in place until 2030 and later drawing board to realize a wide range of wind capacity. Tenders for IJmuiden Ver (four plots of 1 GW each, behind the west coast of the Netherlands, which have not yet been realized) will be launched from 2023, while three new locations of comparable size are under development: Nederwiek, Lagelander and Doordewind, named after a competition among more than six thousand people. The first two parks are located northwest and north of IJmuiden Ver, the latter far north of Gemini. In the spring, the government earmarked 1.7 billion euros for the permit procedures for IJmuiden Ver, nature protection in the North Sea and ship safety.

Germany and Denmark, meanwhile, are not sitting still. What is called: TenneT, not only our national grid operator (TSO), but also for northwestern Germany, has already realized more than seven GW of wind capacity in the German part of the North Sea. According to TenneT, an additional 3.6 GW of offshore wind will be connected to the national grid within five years.

However, Denmark, a pioneer and market leader in wind energy for half a century, is taking the cake. The small North Sea country with 5.5 million inhabitants gets more than half of its energy consumption per inhabitant from offshore wind (more than 2.3 GW) and solar energy (1 GW). Kriegers Flak, the wind farm that was commissioned in the Baltic Sea last year, is already large (604 MW), but it is nothing compared to what Denmark has in store for the future. First and foremost Thor, more than twenty kilometers from the coast near the fishing village Thorsminde (Central Jutland). Thor is to become an 800 to 1000 MW wind farm that will take shape from 2027 and is the first wind farm in the world that the owners will have to pay the state for the electricity at all. Beyond that, there are even more options. By 2030, Denmark will have 10 GW of mega wind turbines – each larger than 5 MW – installed in large offshore parks to make the country independent of fossil fuels.

To connect

For closer cooperation between the North Sea countries – perhaps England will join at a later date – it will also be crucial around 2030 that the physical energy infrastructure is connected. Other technologies (storage and transhipment) are also required for this. At present, electricity from the largest Dutch wind farms is transported via 66 kV cables to an offshore transformer station and converted to direct current (DC) in a 600 MW converter. The power is then brought ashore via a 220 kV cable. A huge transformer on land converts that electricity back from direct current to alternating current (AC) into the 380 kV high voltage grid.

Alternating current is a less suitable solution for mega wind farms located more than 100 kilometers from the coast. As the distance between the source and the release point in the AC increases, the transmission losses and thicknesses of the cables increase, up to thirty percent of the investment cost. Fortunately, in recent years, TenneT has gained extensive experience with high-voltage direct current (HVDC). This applies not only to heavy offshore cables such as Nordlink, 623 kilometers long between Norway and Germany (1400 MW at 500 kV), and the 325 kilometer long Cobra cable between the Netherlands and Denmark (700 MW), but also to a number of newly connected German wind farms. such as DolWin3 (900 MW) and the BorWin1, 2 and 3 brothers (400, 800 and 900 MW respectively).

In addition, something else is involved: When mega wind farms in the future have reached full power and the wind is blowing hard locally, there is an increasing risk that the national high-voltage grid will not be able to cope with that production and collapse. . Therefore, the NSWPH (North Sea Wind Power Hub) consortium, consisting of TenneT, Energinet (the Danish TSO) and Gasunie, has now for a decade developed new concepts for offshore wind. This varies from hybrid wind projects, where wind farm transmissions and interconnections with several North Sea countries are combined, to a ‘hub and spoke’ model. In the latter case, electricity and hydrogen go from a central point (hub) to different distribution points (spokes) to reach the market partners for a more even distribution.

The Energy Islands

Initially, in 2016, TenneT focused on the construction of an energy island on Dogger Bank, a shoal of 13 meters in the North Sea and centrally located between England, Denmark and the Netherlands near East Yorkshire. The grid company wanted an artificial island of 6 km2recycling to connect 100 GW wind farms. That idea turned out to be a little too ambitious. It was not only complicated and quite expensive (more than one and a half billion euros), but also faced sticky political procedures and major concerns from environmental organizations such as the World Wildlife Fund.

Now, after consulting with various market partners and governments, NSWPH has chosen ten energy islands that can transport 10 GW of wind power, significantly smaller in size, but still ten times as large as an average oil platform. Energinet and Elia, the TSOs in Denmark and Belgium, have now taken the plunge and have been developing plans for such islands for a number of years. Green hydrogen to be transported with rebuilt or new pipelines will also play a role in the long run.

An energy toll in the Princess Elizabeth zone – 40 kilometers off the coast of Ostend, where three to four GW of wind capacity is planned – was shelved by the federal government late last year. Instead, in a few years, a concrete structure will be built, which will be filled with sand. The size has not yet been determined. Around or after 2027, that island will connect with Denmark (and perhaps our country) to exchange sustainable electricity.

Denmark is a step further in the preparation, at least in terms of time frame and concretization of the plans. Off the coast of Central Jutland, sixty kilometers behind the planned Thor wind farm, the Danes will start in 2026 with the first phase of the construction of a floating energy island of 120,000 m.2later expanded to 460,000 m2† When everything is ready, 10 GW of wind power can be connected. In the design that the government has released, the meter-high walls stand out that protect the island from the force of the sea on three sides. In addition to a port and a helicopter landing pad, there will be huge sheds with batteries to store excess wind power.

And that’s not all: in 2024, Denmark wants to install a 1 MW electrolyzer in Esbjerg – the logistics center in the wind energy sector more than 100 kilometers south of the Thorsminde fishing village – which will turn wind power into hydrogen, good for production of 90,000 megatons annually. In the meantime, the Danish energy company Ørsted started hydrogen production from two of their 3.6 MW wind turbines at their business park Avedøre Holme in Copenhagen last year.

Climate and marine life

Little is known about the effects of large wind farms on the climate and marine life. However, studies in the United States and Australia have shown that the giant wind turbine blades affect the microclimate. The leaves, with a wingspan of over a hundred meters, mix the air masses and change the air currents. As a result, the air on the ground heats up and it gets a little colder over the wind farms. This can lead to changes in precipitation patterns, both at sea and on land.

However, most of the effects on marine life are caused by noise, especially during piling. Once it has disappeared, positive effects are also possible, for example more food for fish at the funds. Deltares researches this within the framework of WOZEP (Wind at Sea Ecological Program), while NGOs such as Natuur & Milieu and Stichting De Noordzee are committed to increasing biodiversity in and around wind farms via ‘The Rich North Sea’.

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