TenneT Offers Ways to Dutch Offshore Wind Capacity Surge

Transmission system operator TenneT has laid out its ideas for supporting the possible further expansion of offshore wind energy in the Dutch North Sea.

An artist's impression of an island-hub facilitating HVDC converters. Source: TenneT

According to TenneT, the currently standardized connection method – based on Alternating Current (AC) technology – is the best solution for connecting wind farm zones located relatively close to the Dutch coast to the grid.

The electricity generated at these wind farms is transported to a TenneT transformer platform, and then via 220 kV Alternating Current (AC) cables buried in the seabed to an onshore high-voltage substation located near the coast. Each of these standardized connection systems has a capacity of 700MW, and will also be used by TenneT to connect the 1.4GW Borssele wind farm zone, as well as the 1.4GW Hollandse Kust (zuid) and 700MW Hollandse Kust (noord) wind farm zones to the national high-voltage grid.

This connection system would also be usable for the other designated wind energy areas that are relatively close to the coast, according to TenneT.

Far offshore wind farms

It is crucial for further cost reduction and thus the success of offshore wind to support larger scale, TenneT said. In order to be able to realize larger amounts of offshore wind energy, wind farms will also be needed further offshore.

In order to connect offshore wind energy on a large scale and further offshore in a cost efficient way, TenneT believes that the use of direct current connections becomes necessary. Further innovation of these connections should enable these direct current connections to transport power up to 2GW.

TenneT has investigated two options for this. The first option is to use offshore converter platforms to convert the alternating current produced by the wind farms into direct current for efficient transport to the onshore grid. In Germany, TenneT has gained experience in using DC connections in combination with converter platforms; seven such platforms are already in operation, while another two are under construction.

Artificial islands

The second option is based on the construction of an artificial island instead of platforms. This allows the DC converters to be placed and maintained on solid ground. With sufficient scale it is more advantageous to realize one artificial island instead of multiple platforms, according to TenneT.

In addition to the benefits mentioned above, an artificial island can also accommodate port and maintenance facilities and systems for the conversion of wind energy to hydrogen, and can facilitate a so-called WindConnector link to the UK.

A WindConnector is an electricity connection that not only makes it possible to transport offshore wind energy to the onshore grid of one country, but also interconnects the markets of different countries. This can take the form of a direct connection from a wind farm zone to a neighbouring country, or an interconnection between two different wind farm zones.

In addition to transporting wind energy, such a configuration would also facilitate international electricity exchange. The infrastructure can be used in less windy conditions, and would therefore be utilized more efficiently, TenneT said.

Together with The Crown Estate, TenneT has performed a study examining the feasibility of a WindConnector link between the Netherlands and the UK, with the results published on Tuesday, 28 November.