Companies are planning an artificial island for wind power

In the middle of the North Sea is the ideal location for wind turbines – construction and operation, however, seemed almost not possible. Companies are planning a spectacular solution: An artificial island.

Halfway between England and Denmark, in the middle of the North Sea, solid ground under your feet is closer than you think: The so-called Dogger Bank, a sandbank the size of Mecklenburg-Vorpommern, extends just under the surface of the water. In some spots, the water here is not even fifteen metres deep.

It is actually an ideal location for offshore wind turbines – if only the coastlines would not be so far. The installation and operation of a wind farm in the middle of the sea would be extremely expensive and elaborate.

The power supply companies Tennet (Germany/Netherlands) and Energinet.dk (Denmark) want to solve this problem in a spectacular manner: With artificial land. They want to raise an island with an area of several square kilometres on the Dogger Bank. Now they have signed an agreement to do so.

The underlying idea: Surrounded by several thousand wind turbines, the islands shall become a power distribution hub for surrounding countries. The network operators want to connect the islands with several wind farms and thus achieve an output of 70,000 to 100,000 megawatts. By way of comparison: The currently most powerful German power plant in Neurath generates an output of only 4,400 megawatts – and uses brown coal to do so.

On the island, the gained three-phase alternate current is converted to  direct current and is then delivered to the surrounding countries, such as Germany, the Netherlands, Denmark, Great Brittany, Norway or Belgium. By way of the distribution hub, approximately 80 million European households shall benefit from the gained wind energy. Surplus power shall be stored on location or converted to other sources of energy.

According to the companies involved, the proximity between the wind farms and island enables short cable routes and a simplification of infrastructure, which saves costs. Offshore logistics can also be optimised due to personnel, machinery and workshops on site. For this purpose, they would like to provide the island with its own harbour and a landing strip. All in all, the price for wind energy will decrease as a result. According to the initiators, this is an important prerequisite for making renewable energy competitive.

 Landing strip for aeroplanes

Provided with a harbour, a landing strip for aeroplanes, warehouses, workshops and accommodations, the island is to serve as the base for the construction and operation of thousands of wind turbines on the sandbank.

According to an assessment by project partners, facilities with a total capacity of 70 to 100 gigawatts could be linked to the island. With strong wind they would be able to supply up to a hundred million households with electricity, say the companies.

Since the island shall be linked at several spots with the networks of neighbouring North Sea states, it could also become a hub for European electricity trading. Surpluses and deficits in the respective energy systems can be better offset as a result.

 
"Absolutely determined"

“We are absolutely determined to build the island”, emphasises TenneT spokesman Mathias Fischer. But for the time being, the framework conditions must be reviewed and open questions clarified. Now the partners are conducting a feasibility analysis to this end.

“If they arrive at a positive result, we will get started at full speed”, explains Fischer. In the process, several islands could be built on the sandbank if required. According to an assessment by Energinet.dk, it would be possible to complete the first island by about 2035.

In addition to the logistics infrastructure, the island shall also accommodate the converter stations which collect the generated wind energy. They convert energy into direct current and conduct it to land via a submarine cable. With existing offshore wind farms these stations rest on massive stilts between the wind turbines.

"Just as simple as on the mainland"

Converter stations today weigh up to 20,000 tonnes. Their installation is very elaborate. An expensive special ship is required to lift such loads”, says Andreas Wagner, Managing Director of the German Offshore wind Energy Foundation. "With an artificial island, however, the installation would be almost as simple as on the mainland. That reduces the costs significantly."

The island would also provide advantages with regard to maintenance and repairs of wind turbines and network technology. Specialists could stay overnight there, and spare parts and tools also could be stored. A costly service platform in the water would therefore be superfluous.

The construction of an artificial island on the Dogger Bank should not be that much of a major challenge, says TenneT spokesman Fischer. However, two other issues could pose difficulties. “How can the project be integrated in energy markets? And how must the regulatory framework be organised? That must be clarified before construction can begin”, says Fischer.

It also remains to be seen whether the project can be harmonised with nature conservation. Large parts of the sandbank are classified as a Natura 2000 protection area.

“If we take energy transition and climate protection seriously, we must also massively expand offshore wind energy”, says Volker Quaschning from the University of Applied Sciences in Berlin (HTW Berlin). “That is why the project is definitely interesting – even if it comes quite late for Germany, since the conversion of the energy system should be largely completed between 2030 and 2040.”

Transporting energy across the country

However, the scientist points out that the situation is not solved solely with the construction of offshore wind farms. “The electricity must be conducted from the coastline across the countryside to the consumers. But the planned network expansion is not enough to transport very large quantities of offshore wind energy into the south”, explains Quaschning.

The domestic “electricity highways” – whose construction is currently being prepared – shall have a combined capacity of about eight gigawatts. If large quantities of electricity are generated on the Dogger Bank during strong wind, the network could quickly reach its loading limit.

But the construction of other lines in the south is hardly politically feasible. Yet alternatively, says Quaschning, power-to-gas facilities and other storage facilities, which store the electricity from the North Sea as required, could be built on the coastline.

According to current estimates, the implementation of the project will cost 1.3 billion euros. However, that only concerns the expenditures for raising the island – this does not include the costs for the wind turbines and the general infrastructure. It is unclear when the construction of the island would begin. For the time being the project is being reviewed for benefit and feasibility.