ABSTRACT
Offshore wind turbines are designed for a lifetime of 20 to 25 years. Therefore, many wind turbines will have to be removed from the German North Sea and Baltic Sea in the next few years without leaving any residue. With alpha ventus and BARD Offshore 1, two wind farms have already reached about half of their useful lifetime. On the one hand, this process is complex and, on the other hand, requires high efforts of resources within a harsh maritime environment. Due to the high costs of the required installation vessel, the decommissioning must be as efficient as possible. Moreover, the installation vessels could be a limiting factor. They might be requested by other industries and are also required for the installation of new offshore wind turbines. Besides, weather windows with special weather conditions will also be needed for decommissioning. Based on this motivation, a simulation study was carried out which considers the decommissioning of wind turbines in the German North Sea. Real wind farms as well as weather restrictions and process times are taken into account. The results of the simulation show how many additional resources will be needed for the decommissioning of offshore wind turbines in the coming years.
The German government has the aim that renewable energies should cover 80 percent of the electricity supply by 2050 (Deutsche WindGuard, 2019). Offshore wind energy plays a key role here, with 6.5 GW to be installed at sea by 2020 and 15 GW by 2050. These targets have already been met or exceeded, with 1,407 turbines or around 7 GW having been installed by June 2019 (Deutsche WindGuard, 2019).
However, the lifetime of the plants is only 20–25 years. Afterwards, the plants must be dismantled without any residues according to the guideline of the Federal Maritime and Hydrographic Agency (BSH, 2019). Assuming a lifetime of 20 years, more than 1,000 turbines have to be decommissioned between 2030 and 2040, alone in the German North Sea and the German Baltic Sea.
