Power-to-X on open sea: The danish energy island will be smaller, but it will have small satellite platforms

The image shows a visualization of the idea. The final design of the energy island is up to the bidder. Illustration: VindØ Consortium

The North Sea Energy Island will be smaller compared to the original plans, and several of the facilities will be moved out onto floating platforms in the sea surrounding the island.

The Ministry of Climate, Energy and Utilities has concluded that a large, dammed island has a number of disadvantages compared to a smaller island with associated platforms.

This was revealed thanks to a request for access to documents, which included the Ministry’s presentation on the changes in connection with a meeting between the parties that have arranged it.

Earlier this summer, the Danish Energy Agency postponed the tender until 2023 and then changed the framework for how the artificial island should look. The documents show what was behind that reconsideration and reveal more details about the framework for the upcoming tender.

Power-to-X on platforms

The new tender will still contain the requirement that the island must be able to function as a transmission link for a total of 10 GW of offshore wind.

The island will still house equipment for electricity transmission as well as a harbour and areas for accommodation and operations on the island. However, the fixed island can be combined with platforms for some of the facilities.

Below, you can see a sketch of a permanently dammed island and the new model, in which some facilities are moved out onto platforms.

Illustration: Klima-, Energi- og Forsyningsministeriet

According to the documents, it appears that areas intended for Power-to-X can be moved off the island. It also appears that it is technically possible to implement this on the platforms. Power-to-X is therefore still part of the overall plan for the energy island and is expected to be realised at the same time as the expansion of the wind farms.

“We have learned more...”

By moving some of the facilities out onto platforms, it is possible to build a smaller island. Under the heading “We have learned more...”, the Ministry states that this provides a number of advantages.

First of all, the construction is not that complicated because the island itself can be smaller. This means that the island can start producing electricity sooner. Although the tender has been pushed to 2023, the island is therefore still expected to be ready to supply power in 2033.

At the same time, another problem is solved. At present, it is not entirely clear how much space will actually be used for the Power-to-X technology. If you have an island where parts of the facilities have been moved out onto platforms, it is easier to add more space if needed.

The Ministry also points out that a smaller island with platforms will put less pressure on the climate and the environment. However, this point is not elaborated further.

Platforms may help optimize the energy island

Ultimately, the design of the energy island is up to the winner of the tender. It is thus still unclear what the energy island will look like, but the idea of moving facilities from the island itself and onto platforms could definitely be a sensible way to optimize the concept, according to Erik Damgaard Christensen, professor at DTU who has, among other things, researched wind turbines and other types of structures in water.

First of all, the area required for the island will be smaller, as the Ministry also mentions.

If the substations also end up being moved onto platforms, the current can be transformed into direct current before it is sent to the island itself. This could be an advantage because direct current is better suited for transport over long distances thanks to less power loss.

“There will be a great many turbines, and they will be placed in a very large area with lots of cables. Therefore, one could well imagine that it would be quite sensible to have some small satellites with substations,” Erik Damgaard Christensen says.

In terms of engineering, Erik Damgaard Christensen also believes that it is possible to build and secure platforms on the open sea. If the platform is built high enough, it can easily be protected against the sea and the high waves in the North Sea.

“We already have quite a bit of knowledge about how high a platform in the North Sea must be placed thanks to the gas and oil fields. Of course, the research is still ongoing, but it’s common practice to place substations on platforms,” he says.

Difference in costs is unknown

The total cost of establishing the energy island and the associated wind farms is DKK 210 billion. Around five percent of that will go towards building the island itself.

However, it is not entirely clear what the construction costs look like for a more flexible island. All cost estimates for the construction of the island are excluded from the documents we were granted access to because the Ministry considers that it could impair the state’s negotiating position if they are published.

In the documents, the Ministry states that the latest cost estimates do not show any advantages of economies of scale in aggregating everything on an island. It also appears that, according to the Ministry, there are no significant differences between the construction costs of the two types of islands.