A meshed grid
Until now, all North Sea wind farms have been connected individually to the onshore grid. With the creation of a modular grid or ‘power socket’, wind farms will be connected to a high-voltage substation located on an offshore platform, which will, in turn, be connected to the onshore grid. The exact design of the modular grid and its regulatory framework are currently being examined, in collaboration with the various stakeholders.
An international direct-current platform
In the long term, the modular grid infrastructure will then be connected to an international platform using direct-current connections. These make it possible to transmit greater quantities of power over longer distances. Some of Belgium's neighbouring countries, like the United Kingdom and the Netherlands, are also working to develop grids in their territorial waters in the North Sea.
Such an international platform will facilitate access to other types of energy, particularly hydropower in Scandinavia. These resources could be used in the event of there being insufficient wind in the North Sea. The connections will also allow wind power to be stored in dedicated infrastructure when a surplus of energy is generated. This new North Sea grid will enable Belgian consumers to be supplied with green energy, even when there is no wind!
To ensure that wind farms in the North Sea are optimally connected to Elia's onshore grid, the solution is a modular offshore grid or offshore ‘power socket’.
Elia is currently consulting with stakeholders – the relevant authorities and the operators of the offshore wind farms that are still to be built (Mermaid, Northwester II, Rentel and Seastar) – to decide on the best way to implement this offshore grid. A modular grid is ideal from a technical, economic but also environmental viewpoint as it will facilitate shared use of the grid by as many wind farms as possible.
One major long-term objective of the offshore ‘power socket’ is to concentrate all the available electrical capacity at a single point, so that the energy generated offshore can be transmitted to centres of consumption via direct-current infrastructure to be built offshore. With this move, Elia and its partners want to lay the foundations for a vast direct-current offshore grid in Europe.
Stage one: consolidating the onshore grid
First of all, Elia consolidated its onshore grid in coastal areas, which was an essential step to allow for a massive injection of energy in that region for onward transmission to the main centres of consumption inland.
To achieve this, Elia:
- laid a new 150-kV underground line between the Koksijde and Slijkens substations;
- upgraded the Slijkens high-voltage substation; and
- strengthened the connection between Zeebrugge and Blauwe Toren with two 150-kV cables, plus an extra cable between the Bruges and Blauwe Toren substations.
These developments made it possible to connect the first wind farms, providing a capacity of approximately 900 MW. Elia also began implementing the Stevin project in early 2015. This involves upgrading the high-voltage grid along the coast by installing a 380-kV line between Zomergem and Zeebrugge, so that power generated by offshore wind farms can be transmitted inland.
Stage two: determining the design of the modular offshore grid or ‘power socket’
Elia is currently working with the various stakeholders to determine the best solution from a technical, economic and environmental viewpoint.