A new study by Frontier Economics, commissioned by Bundesverband Windenergie Offshore and Bundesverband der Energie- und Wasserwirtschaft, finds that the economically optimal level of overdimensioning for offshore grid connections in the German North Sea is around 5–10%. The analysis indicates that a uniform requirement of 20%, as outlined in the 2025 area development plan, would lead to unnecessary system costs.
The study, Analysis of a socio-economically optimal overdimensioning of offshore wind grid connections, examines four undeveloped offshore areas in the German North Sea. It evaluates different combinations of wind farm capacity and grid connection capacity to determine the balance of costs and benefits for the energy system.
The results show that the socio-economically optimal level of overdimensioning ranges from 5–10%, depending on the site and scenario. At this level, curtailment of generated electricity is estimated at about 3–4%. From a project developer perspective, however, the economic optimum is lower, at roughly 2.5–5%, meaning the system-wide optimum exceeds the level that developers would typically choose based on project economics.
The study concludes that fixed overdimensioning requirements can increase electricity costs if they exceed the economically efficient range. Developers already tend to overdimension within economically viable limits, and site-specific approaches are considered more appropriate than uniform requirements.
The analysis also highlights the need for broader optimisation of offshore wind deployment. This includes more efficient use of available sites and grid infrastructure, improvements in full-load hours to increase utilisation of turbines and grid connections, and greater international cooperation on offshore development in neighbouring areas.
According to the industry organisations, several measures could support more cost-efficient offshore wind expansion. These include reducing capacity density on new sites to below 10 MW per square kilometre, planning sites to minimise wake losses between wind farms, and expanding cross-border cooperation, including potential development of suitable offshore areas in Denmark.
Overdimensioning refers to installing more wind capacity than the export cable capacity available for a wind farm. The approach can improve utilisation of grid infrastructure during periods of low wind. During periods of high wind generation, however, the grid connection cannot export all produced electricity and the surplus generation must be curtailed.
The study by Frontier Economics examines four offshore sites in the German North Sea: N-10, N-12, N-17+20 and N-19. Its assumptions build on earlier research, International Optimisation of Full Load Hours in the German Bight – Cross-Border Radials, by Fraunhofer IWES, also commissioned by Bundesverband Windenergie Offshore and Bundesverband der Energie- und Wasserwirtschaft. The studies aim to provide a scientific basis for improving offshore wind development planning in Germany.
