Enhancing Blue Economy Through Multi-Use Offshore Wind Farms: Hydrodynamic Impacts and Opportunities for Sustainable Resource Use

The European Green Deal's goal of transforming the EU into a modern, resource-efficient and competitive economy depends on the establishment of a sustainable blue economy. This study pursues a multi-use resource strategy to promote the Blue Economy under the EU Green Deal, with a particular focus on the potential of multi-use offshore wind energy and low trophic level aquaculture. The multi-use of offshore wind farms (OWFs) for the dual purpose of energy and food production exemplifies the benefits of multi-use of marine space, such as promoting restoration and regeneration, nutrient and carbon sequestration or improving water quality. This study is a fundamental step in our efforts to simulate realistic hydrodynamic conditions at the Meerwind-OWF site (German Bight, North Sea).

We investigate the interactions between OWF monopiles and wind-driven waves, with a focus on how these structures influence local and regional hydrodynamics. The model captures detailed transitions from broad ocean boundaries down to near foundation scales, providing insights into flow modification and changes in wave patterns around the OWF. To this end, a high-resolution 3D modelling framework (coupled circulation-wave-sediment-biogeochemistry) based on unstructured grids is employed, allowing an effective transition in resolution from ~2 km at open marine boundaries to ~2 m near foundations. Our analysis reveals a reduction in mean current velocities near the structures and changes in wave heights, which affect the potential energy distribution of the surrounding water column.  The monthly potential energy anomaly increases outside the OWF, affecting an area well beyond the farm boundaries, while decreasing within the farm boundaries. The monopiles reduce the monthly significant wave height (Hs) within the OWF and beyond. The prevailing westerly waves affect the tidal asymmetry, particularly on the eastern side of the piles. This results in an asymmetry in the intensity of turbulent wakes on either side of the piles, in both monthly and tidal timescales.  These changes can significantly affect sediment transport, nutrient dynamics, and habitat conditions around the OWF.

Building on these findings, we have developed a series of what-if scenarios to assess the potential of combining OWFs with aquaculture facilities. The scenarios explore different configurations within and around OWFs and assess their impact on ocean dynamics, nutrient cycling and ecosystem health. By varying factors such as climate change, the spatial arrangement of monopiles or operational strategies, the scenarios provide critical insights into optimising multi-use strategies. For instance, co-locating low trophic level aquaculture in OWF can enhance nutrient uptake and improve local water quality, while also contributing to carbon sequestration and supporting biodiversity. This approach is consistent with the principles of sustainable blue growth, which emphasises the importance of maximising economic benefits while mitigating environmental impacts. By integrating advanced modelling techniques and scenario-based analysis, the study provides a robust framework for assessing the trade-offs and synergies of multi-use ocean space. Our findings contribute to a broader understanding of how multi-use offshore platforms can be used to support the transition to a sustainable blue economy. This can be useful for policy makers, industry stakeholders and coastal managers.