The number of wind turbines in the North Sea is not only growing explosively, but we are also exchanging more and more electricity with our neighboring countries. In the future will our electricity come from a special energy island at sea?
In the next thirty years, the production of wind power in the North Sea must increase tenfold, spoke Prime Minister Mark Rutte recently met with his colleagues from Belgium, Germany and Denmark. There are now about 2.5 gigawatts of wind turbines in the Dutch North Sea. In 2031 that should already be 20 gigawatts. But the number of wind farms will probably continue to grow even after that, because we will use less fossil fuels and more electricity.
But windmills don’t constantly produce electricity like a coal-fired power station can. If there is no wind or if there is little wind, the wind farm will yield nothing or less. At those moments, we will have to rely on the import of electricity from abroad. If there is a strong wind here, we have a surplus and we want to export electricity.
If it is up to the four North Sea countries, this will be done in about fifteen years’ time via special energy islands. These hubs collect the power from gigantic wind farms and are connected to several neighboring countries. This creates a kind of separate electricity grid at the bottom of the sea, with the islands as high-voltage stations.
Example of an electricity and hydrogen network with islands in the North Sea.
Example of an electricity and hydrogen network with islands in the North Sea. Photo: North Sea Wind Power Hub
‘The further out to sea, the better’
“If you are going to build more and more wind farms at sea, it becomes very attractive to also realize more connections abroad,” says wind energy expert Jasper Vis of TenneT, the grid operator that connects the Dutch offshore wind farms to the electricity grid. With a view to the growth of the number of wind farms, TenneT developed the island concept in 2016, which has been further developed ever since.
“The advantage of this connection to several countries is that you can sell the electricity to the country that needs it most at that moment,” says Emiel van Druten, energy consultant at Witteveen+Bos. He was involved in several studies into the possibilities of energy islands.
Since the North Sea is very busy close to the coast, partly due to the many ships around the ports of Rotterdam and IJmuiden, wind farms will be built increasingly further from the coast in the future. This makes building an island more attractive: from a large wind farm in the middle of the North Sea you could lay cables to the Netherlands, Denmark, Germany, Norway and the United Kingdom. “The further out to sea, the more favorable compared to traditional connections to one country,” says Van Druten.
Belgium preys on Danish electricity
Denmark is the first country to have concrete plans to build such an island. In the course of next year it should be known which company will do this and in eleven years it should actually be operational. “Denmark already has a lot of wind energy,” explains Van Druten. “If they want to expand further, surpluses will increasingly arise. Such an island to be able to export energy therefore fits well in the strategy of the Danish government.”
Belgium is first in line for a connection to the island, because our southern neighbors themselves have little space for windmills at sea. The Netherlands is also exploring a connection with the Danish island.
Concept drawing of the Danish energy island.
Concept drawing of the Danish energy island. Photo: Danish Ministry of Energy
Sand or concrete?
Exactly what such an energy island should look like is still uncertain. An island of sand has to be defended with expensive sea walls, but could offer a relatively large amount of space for the gigantic inverters needed to direct wind power towards land. They still have to be built on steel platforms at sea, which also costs a lot of money. Denmark is considering a more compact construction with caissons, a type of concrete barge that is sunk into the seabed.
It is possible that space can also be made on energy islands for factories that convert wind power into green hydrogen. This can then be brought to the mainland by pipeline. That costs a lot less money than bringing all the power ashore with cables, a survey showed last year study commissioned by the Netherlands Enterprise Agency.
If the Netherlands builds its own energy island, it will be completed in the second half of the 1930s at the earliest, the experts believe. The wind farms that will be built up to and including 2031 will all have a ‘traditional’ cable to the mainland, although TenneT says it will. explore whether a cable to the United Kingdom can also be laid at one of the future wind farms.
In any case, good international cooperation is crucial to get the most out of the North Sea as a power plant, says Vis of TenneT. “We are working hard on that. It must of course fit together in technical terms.”