Connection of Bornholm’s power grid to the energy island poses an extra challenge

Constructing energy islands is a complex project in itself and requires that many bright minds get together and think innovatively. Energinet will now also work to connect Bornholm’s small AC transmission grid to the large DC system. Obviously in a way which ensures that the islanders always have electricity in their sockets and intact household appliances.

The satisfaction is noticeable on Bornholm after Energinet announced its plan in January to work to supply green power to the islanders from the local energy island.

“That’s great news. Seeing that we’re to house the onshore facilities of the energy island, the power from the wind turbines should obviously also benefit the citizens and businesses of Bornholm,” commented Jacob Trøst (Cons.), the new mayor of Bornholm, in a press release. He promises the islanders that he will monitor the situation closely and safeguard the interest of Bornholm in being connected to the system.

“Seeing that we’re building an energy island in the islanders’ backyard, so to speak, they’re very keen on having green electricity from the island in their sockets. We’d like to comply with their wish. Right now, they have another generation of electricity that’s not as green as the one we can offer from the energy island,” says Kim Søgaard Mikkelsen, who is Energinet’s project manager for the Bornholm Energy Island.

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Many bright minds needed
Energinet must now find out how to meet this challenge.

“Constructing energy islands is a complex and innovative process in itself and requires a lot of bright minds and a lot of innovation. We know HVDC plants, and we know large wind farms. But combining them with the energy islands in the way we envisage – this hasn’t previously been done on this scale anywhere in the world,” says Laurids Dall, Energinet’s subproject manager on the electricity system on the energy island. 

An energy island is different from the normal electricity system. It will be based exclusively on computer-controlled technologies that operate sensitive components. Several offshore wind farms and several HVDC systems, possibly from multiple suppliers, must be set very precisely to match each other on the energy island.

Added complexity
Connecting the small electricity system of Bornholm to the energy island of 2 GW adds further complexity to the project.

“A small disturbance or change in voltage on the energy island, for example in relation to how the wind is blowing or the wind turbines switch on and off, can easily cause a relatively large change in the local system on Bornholm. This may have a major impact on the electricity supply and the electricity supply quality experienced by the islanders. We must therefore solve the task in a way that safeguards the power quality and the security of supply on Bornholm. For example, we must avoid the scenario which we experienced a few years ago on Anholt, where household appliances broke down,” stresses Laurids Dall.

Experience available
He is confident: “We don’t know 100 per cent what the solution is, but we believe that it can be developed in cooperation with our suppliers. We can, for example, draw on experience from the Kriegers Flak offshore wind farm. It isn’t an energy island, but it’s the closest thing we have to one. During 2022, we must conduct a market dialogue with our HVDC suppliers and hear how they see the solutions.”

At Bornholms Energi & Forsyning, CEO Claus M. Andersen is pleased that Energinet will work to connect Bornholm to the green electricity.

“It’s good for Bornholm, because it will increase security of supply and provide lots of opportunities. For example, we’ll be able to attract energy-intensive companies to Bornholm or establish Power-to-X production. I’m fully convinced that this will contribute to ensuring that the corporate sector will look towards Bornholm.”

Important role for Bornholm
He points out that it will be the first time in the world that a large DC system will be connected with a small AC system, and Bornholm will thus play an important role in the technological development – a development that may be brought into play elsewhere in the world. On Bornholm, there are also expectations that the development may form the basis of new jobs, educational activities or even energy tourism.

“We’re involved in finding future green energy solutions, and this may have a lot of positive effects, for example in relation to outside interest in Bornholm,” says Claus M. Andersen.

National Centre for Green Energy
The possible connection is completely in line with Bornholm’s vision to become a national and an international hub for green energy, and funding is being applied for to establish the National Centre for Green Energy – a collaboration in which Energinet and several large companies are also involved.


Bornholms Energi & Forsyning is used to being part of finding the energy solutions of the future. The utility company has been involved in several development projects that have attracted attention around the world. Claus M. Andersen is here photographed at the map showing the 56 countries with which Bornholms Energi & Forsyning has been in contact in this connection.