Energinet assesses Borholm energy island transmission system potential

4C Offshore | Tom Russell
By: 07/01/2022 Energinet

Energinet, the Transmission System Operator (TSO) for Denmark, has revealed that it is now ready to design the upcoming high-voltage station to support the connection of the energy island off Bornholm in the Baltic Sea.

The artificial island aims to connect and distribute power from the surrounding offshore wind farms. The Energy Island is a completely new concept for capture, distribution and utilisation of power from offshore wind. It will be situated in the Baltic with a starting capacity of 2 GW from connected offshore wind farms. It is also expected to support new technologies, such as Power-to-X.

The preliminary conclusion comes after an initial analysis which Energinet said shows that it will probably be technically possible to connect the energy's power cables to the Bornholm electricity grid without compromising either stability or security of supply in the entire electricity grid on Bornholm or elsewhere. As it is estimated, this can be done without compromising the schedule of the overall project.

Furthermore, according to Energinet, the analysis shows that there will be a socio-economic saving by connecting the Bornholm electricity grid to the energy's future power connections. Currently, Bornholm is connected to the Zealand electricity grid via a submarine cable to Sweden. To maintain security of supply, Energinet currently operates a power plant on Bornholm to be ready to produce electricity in the event of a break or failure of the power cable to Sweden. This expense can be saved if the Bornholm electricity grid is connected to the energy island's cables.

On the basis of the analysis, Energinet will now start developing the technological solutions.

Over the past six months, Energinet has carried out an initial analysis of technical possibilities and financial consequences of connecting the Bornholm electricity grid to Bornholm's future electricity infrastructure, including offshore wind farms and the energy island.

The preliminary assessments from the analysis show that it will probably be possible to connect the Bornholm electricity grid to the energy island's electricity infrastructure with a 60 kV connection.

Estimated of costs for the various technical solution options are still subject to uncertainty, but right now the most expensive solution is estimated to cost approx. DKK 230 million extra in construction costs.

This expenditure must be kept up against a saving of the current expenditure on fossil reserves, i.e. costs of keeping a power plant ready to produce electricity in the event of a fault or break in the cable between Bornholm and Sweden. Over 40 years, the savings will amount to DKK 676 million according to Energinet.


As part of the Danish climate agreement of June 2020, it was decided to build two energy islands, in the Baltic and North Seas respectively, linked to offshore wind farms that together can provide 5 GW and cover the electric consumption for approx. 5 million households in Denmark and nearby countries.

In addition to the aforementioned Borholm energy island, Denmark envisages the establishment of an artificial island in the North Sea that will serve as a hub for offshore wind farms supplying 3 GW of energy, with a long-term expansion potential of 10 GW. The artificial island in the North Sea and the surrounding offshore wind farms will be established approximately 80 km off the coast of Thorsminde, a town in Jutland.