A rendering of Denmark’s energy island.
Courtesy of the Danish Energy Agency
Denmark’s energy islands will be a hub for transmitting wind-generated electricity and producing green hydrogen.
The energy islands will create a new power system that will be able to transmit offshore wind power over large distances.
This article is part of “The Great Energy Transition” series.
Denmark is building two energy islands that could accelerate Europe’s green transition.
The islands – which will consist of one artificial island in the North Sea and one built on the island of Bornholm in the Baltic Sea – will produce wind energy and, in the future, green hydrogen power.
The projects signal a new, integrated approach to generating renewable energy. Located 100 km from the Danish mainland, the artificial North Sea island has the potential to supply electricity to several countries alongside Denmark, including the Netherlands, the UK, and Belgium – a scale which hasn’t been previously possible. As well as contributing to the EU’s 2050 net zero target, the renewable energy source would lessen Europe’s reliance on Russian gas.
Jacob Østergaard, professor and head of the Department of Wind Energy at the Technical University of Denmark, told Insider that the project is a “massive undertaking”.
“It’s a completely new type of energy system that we are building,” he added.
A Danish innovation with implications across Europe
The North Sea island, which is set to cost €28 billion, will be made up of a central hub made of steel, concrete, and sand, and will be surrounded by a series of platforms and wind turbines. No one will live there permanently — but there may be accommodation for short stays for workers.
The Bornholm island will be on a similar scale and could provide electricity to Germany and Sweden in the future. For the 39,000 people who live on the island, the project is welcome – a recent poll by a local television station found that 85% of islanders are in favor of the project, which will consist of a huge transformer station on the south side of the island and a network of wind turbines.
Klaus Vesløv, director of Public Affairs at Bornholm Energy & Supply, told Insider that while there has been some backlash to the size of the transformer station, the majority of islanders hope that the project will bring jobs and energy security.
“Energy policy is also a security policy, in terms of not being reliant on Russian gas,” Vesløv said. “This part of the discussion has actually moved the [green] agenda higher up.”
Renewable energy isn’t a new endeavor for Denmark – they were the first country in the world to construct an offshore wind farm back in 1991. What’s different about the energy islands, though, is the way that they will convert and transmit the electricity that they produce.
Most traditional offshore wind farms transmit electricity directly to the mainland. While interconnectors have facilitated some electricity trade, the ability to share wind-generated energy between countries is currently limited. That means that surplus wind power can sometimes go to waste.
Hanne Storm Edlefsen, director for Energy Islands at Danish electricity operator Energinet, which is leading the project, told Insider that the energy islands will be “innovative, technological stepping stones” in the race to create an integrated, high voltage power system in the North and Baltic Seas.
“[The islands] will make it possible to harvest huge amounts of offshore wind energy and transmit it over long distances to decarbonize energy use even in European countries with limited or no coastline access to the sea,” Edlefsen said.
At first, the North Sea island will supply 3 gigawatts (GW) of electricity. Eventually, it will have a capacity of 10 GW.
The hub will house high-voltage equipment to collect and convert power from alternating current to direct current. Direct current is able to transmit electricity over much larger distances.
Edelfsen said that this innovation means that the energy islands will be able to be built much further out to sea than traditional offshore wind farms. It also means that the energy islands will be able to connect with more than one country and energy market at a time.
Potential for producing green hydrogen
The first islands could be gradually extended to develop an offshore grid infrastructure with multiple hubs, according to Østergaard.
“If you want to harvest energy far from shore it is much more efficient to collect the energy in hubs and then transmit to shore – instead of many individual cables from each wind farm going to shore,” Østergaard said.
He added: “Denmark should help Europe to fulfill this green transition and collaborate with all countries around the Baltic Sea and the North Sea.”
Once fully established, Edlefsen told Insider that the electricity produced on the energy islands could also be used to produce green hydrogen for sectors like heavy industry, aviation, and shipping.
“The development of hydrogen is fast-moving,” Edlefsen said. “Already studies show that offshore production of hydrogen and the transport of hydrogen in pipelines on the seabed to the shores will be both feasible and in some cases economically viable as compared to onshore production.”
Green hydrogen could be especially important on Bornholm Island – around 60,000 ships pass the island each year.
“Bornholm could become a bunker hub for those ships,” Vesløv told Insider. “We could utilize those vast amounts of energy to turn them into green fuels [for shipping].” Once completed, Bornholm Island will produce 6GW of electricity – enough to power 7 million homes.
“The reality is nobody has done this before on this scale,” Vesløv said, adding that Denmark’s islands will be a “blueprint”.
“The world is going to build a lot of energy islands,” he said.