About Offshore Interconnections

Offshore interconnection involves the use of seaward cables to connect two or more offshore platforms, creating transmission capacity that benefits onshore grid connection points. This approach offers several options for bringing the electricity onshore and enhancing the robustness and flexibility of the energy system. A differentiation can be made between national and international offshore interconnection.

National interconnection involves linking offshore grid connection systems within the German Exclusive Economic Zone (EEZ). This can reduce onshore grid bottlenecks, create greater redundancy in the grid connection of offshore wind parks, save costs in congestion management, and reduce the curtailment of renewable energies. Due to the shorter distances at sea, investment costs are also significantly lower compared to onshore measures.

In international offshore interconnection, offshore grid connection systems from the German EEZ are linked to systems from the EEZ of countries bordering the North Sea. Such interconnections across national borders strengthen international electricity trading and promote the integration of the European electricity markets. This leads to lower electricity prices overall and promotes the integration of renewable energies.

Complex offshore grids require modular and flexible planning

Interconnecting offshore platforms at sea is a challenging goal. Amprion is gradually increasing the degree of interconnection to master the complexity of offshore grids. Initially, two offshore systems will be connected with a DC cable. By interconnecting systems from the same manufacturer, the technological challenge is minimized. However, it is not possible to expand or later connect these systems with those from other manufacturers. Despite this limitation, the positive effects of offshore interconnections remain. To avoid compromising national offshore expansion targets, we are planning appropriate fallback levels on the path to larger offshore grids. Simple point-to-point systems serve as the lowest fallback level. Connecting more than two systems can offer benefits such as redundancy, flexibility, and trading opportunities with other countries. However, suitable technologies must be developed first. In large offshore grids, electrical components from different manufacturers must work together. Experts refer to this as the interoperability or multi-vendor capability of HVDC systems. Amprion is involved in several research and development projects to establish the standards that are still missing.